ATMEL AT86RF231-ZU

Features
• High Performance RF-CMOS 2.4 GHz Radio Transceiver Targeted for IEEE 802.15.4™,
ZigBee®, 6LoWPAN, RF4CE, SP100, WirelessHART™ and ISM Applications
• Industry Leading Link Budget (104 dB)
– Receiver Sensitivity -101 dBm
– Programmable Output Power from -17 dBm up to +3 dBm
• Ultra-Low Current Consumption:
– SLEEP
= 0.02 µA
– TRX_OFF
= 0.4 mA
– RX_ON
= 12.3 mA
– BUSY_TX
= 14 mA (at max. Transmit Power of +3 dBm)
• Ultra-Low Supply Voltage (1.8V to 3.6V) with Internal Regulator
• Optimized for Low BoM Cost and Ease of Production:
•
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•
•
•
•
•
•
– Few External Components Necessary (Crystal, Capacitors and Antenna)
– Excellent ESD Robustness
Easy to Use Interface:
– Registers, Frame Buffer and AES Accessible through Fast SPI
– Only Two Microcontroller GPIO Lines Necessary
– One Interrupt Pin from Radio Transceiver
– Clock Output with Prescaler from Radio Transceiver
Radio Transceiver Features:
– 128-byte FIFO (SRAM) for Data Buffering
– Programmable Clock Output, to Clock the Host Microcontroller or as Timer
Reference
– Integrated RX/TX Switch
– Fully Integrated, Fast Settling PLL to support Frequency Hopping
– Battery Monitor
– Fast Wake-Up Time < 0.4 msec
Special IEEE 802.15.4-2006 Hardware Support:
– FCS Computation and Clear Channel Assessment
– RSSI Measurement, Energy Detection and Link Quality Indication
MAC Hardware Accelerator:
– Automated Acknowledgement, CSMA-CA and Retransmission
– Automatic Address Filtering
– Automated FCS Check
Extended Feature Set Hardware Support:
– AES 128-bit Hardware Accelerator
– RX/TX Indication (external RF Front-End Control)
– RX Antenna Diversity
– Supported PSDU data rates: 250 kb/s, 500 kb/s, 1 Mb/s and 2 Mb/s
– True Random Number Generation for Security Application
Industrial and Extended Temperature Range:
– -40°C to +85°C and -40°C to +125°C
I/O and Packages:
– 32-pin Low-Profile QFN Package 5 x 5 x 0.9 mm³
– RoHS/Fully Green
Compliant to IEEE 802.15.4-2006 and IEEE 802.15.4-2003
Compliant to EN 300 328/440, FCC-CFR-47 Part 15, ARIB STD-T66, RSS-210
Low Power
2.4 GHz
Transceiver for
ZigBee,
IEEE 802.15.4,
6LoWPAN,
RF4CE, SP100,
WirelessHART,
and ISM
Applications
AT86RF231-ZU
AT86RF231-ZF
8111C–MCU Wireless–09/09
AT86RF231
1. Pin-out Diagram
D IG 3
1
D IG 4
2
AVSS
3
R FP
4
R FN
5
AVSS
X TA L 2
X TA L 1
AVSS
E V DD
A V DD
AVSS
32 31 30 29 28 27 26 25
24
exposed paddle
IR Q
/SEL
22
M OSI
21
D VSS
20
M IS O
6
19
SC LK
D VSS
7
18
D VSS
/R S T
8
17
9 10 11 12 13 14 15 16
C LKM
DE V D D
DV D D
DV D D
D VSS
DI G 2
S L P _ TR
A T86 R F2 3 1
D VSS
23
AVSS
DI G 1
Note:
AVSS
AT86RF231 Pin-out Diagram
AVSS
Figure 1-1.
The exposed paddle is electrically connected to the die inside the package. It shall be soldered to
the board to ensure electrical and thermal contact and good mechanical stability.
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1.1
Pin Descriptions
Table 1-1.
Pin Description AT86RF231
Pins
Name
Type
Description
1
DIG3
Digital output (Ground)
1. RX/TX Indicator, see Section 11.5
2. If disabled, pull-down enabled (AVSS)
2
DIG4
Digital output (Ground)
1. RX/TX indicator (DIG3 inverted), see Section 11.5
2. If disabled, pull-down enabled (AVSS)
3
AVSS
Ground
Ground for RF signals
4
RFP
RF I/O
Differential RF signal
5
RFN
RF I/O
Differential RF signal
6
AVSS
Ground
Ground for RF signals
7
DVSS
Ground
Digital ground
8
/RST
Digital input
Chip reset; active low
9
DIG1
Digital output (Ground)
1. Antenna Diversity RF switch control, see Section 11.4
2. If disabled, pull-down enabled (DVSS)
10
DIG2
Digital output (Ground)
1. Antenna Diversity RF switch control (DIG1 inverted), see Section 11.4
2. Signal IRQ_2 (RX_START) for RX Frame Time Stamping, see Section 11.6
3. If functions disabled, pull-down enabled (DVSS)
11
SLP_TR
Digital input
Controls sleep, transmit start, receive states; active high, see Section 6.5
12
DVSS
Ground
Digital ground
13
DVDD
Supply
Regulated 1.8V voltage regulator; digital domain, see Section 9.4
14
DVDD
Supply
Regulated 1.8V voltage regulator; digital domain, see Section 9.4
15
DEVDD
Supply
External supply voltage; digital domain
16
DVSS
Ground
Digital ground
17
CLKM
Digital output
Master clock signal output; low if disabled, see Section 9.6
18
DVSS
Ground
Digital ground
19
SCLK
Digital input
SPI clock
20
MISO
Digital output
SPI data output (Master Input Slave Output)
21
DVSS
Ground
Digital ground
22
MOSI
Digital input
SPI data input (Master Output Slave Input)
23
/SEL
Digital input
SPI select, active low
24
IRQ
Digital output
1. Interrupt request signal; active high or active low; configurable
2. Frame Buffer Empty Indicator; active high, see Section 11.7
25
XTAL2
Analog input
Crystal pin, see Section 9.6
26
XTAL1
Analog input
Crystal pin or external clock supply, see Section 9.6
27
AVSS
Ground
Analog ground
28
EVDD
Supply
External supply voltage, analog domain
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Table 1-1.
Pin Description AT86RF231 (Continued)
Pins
Name
Type
Description
29
AVDD
Supply
Regulated 1.8V voltage regulator; analog domain, see Section 9.4
30
AVSS
Ground
Analog ground
31
AVSS
Ground
Analog ground
32
AVSS
Ground
Analog ground
Paddle
AVSS
Ground
Analog ground; Exposed paddle of QFN package
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1.2
1.2.1
Analog and RF Pins
Supply and Ground Pins
EVDD, DEVDD
EVDD and DEVDD are analog and digital supply voltage pins of the AT86RF231 radio
transceiver.
AVDD, DVDD
AVDD and DVDD are outputs of the internal 1.8V voltage regulators. The voltage regulators are
controlled independently by the radio transceivers state machine and are activated dependent
on the current radio transceiver state. The voltage regulators can be configured for external
supply.
For details, refer to Section 9.4 “Voltage Regulators (AVREG, DVREG)” on page 110.
AVSS, DVSS
AVSS and DVSS are analog and digital ground pins respectively. The analog and digital power
domains should be separated on the PCB.
1.2.2
RF Pins
RFN, RFP
A differential RF port (RFP/RFN) provides common-mode rejection to suppress the switching
noise of the internal digital signal processing blocks. At board-level, the differential RF layout
ensures high receiver sensitivity by rejecting any spurious emissions originated from other digital
ICs such as a microcontroller.
A simplified schematic of the RF front end is shown in Figure 1-2 on page 5.
Figure 1-2.
Simplified RF Front-end Schematic
PCB
AT86RF231
RFP
RFN
0.9V
M0
LNA
RX
PA
TX
CM
Feedback
RXTX
The RF port is designed for a 100Ω differential load. A DC path between the RF pins is allowed.
A DC path to ground or supply voltage is not allowed. Therefore, when connecting an RF-load
providing a DC path to the power supply or ground, AC-coupling is required as indicated in Table
1-2 on page 6.
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The RF port DC values depend on the operating state, refer to Section 7. “Operating Modes” on
page 33. In TRX_OFF state, when the analog front-end is disabled (see Section 7.1.2.3
“TRX_OFF - Clock State” on page 35), the RF pins are pulled to ground, preventing a floating
voltage.
In transmit mode, a control loop provides a common-mode voltage of 0.9V. Transistor M0 is off,
allowing the PA to set the common-mode voltage. The common-mode capacitance at each pin
to ground shall be < 30 pF to ensure the stability of this common-mode feedback loop.
In receive mode, the RF port provides a low-impedance path to ground when transistor M0, see
Figure 1-2 on page 5, pulls the inductor center tap to ground. A DC voltage drop of 20 mV
across the on-chip inductor can be measured at the RF pins.
1.2.3
Crystal Oscillator Pins
XTAL1, XTAL2
The pin XTAL1 is the input of the reference oscillator amplifier (XOSC), XTAL2 is the output. A
detailed description of the crystal oscillator setup and the related XTAL1/XTAL2 pin configuration can be found in Section 9.6 “Crystal Oscillator (XOSC)” on page 116.
When using an external clock reference signal, XTAL1 shall be used as input pin.
For further details, refer to Section 9.6.3 “External Reference Frequency Setup” on page 117.
1.2.4
Analog Pin Summary
Table 1-2.
Analog Pin Behavior - DC values
Pin
Values and Conditions
Comments
RFP/RFN
VDC = 0.9V (BUSY_TX)
VDC = 20 mV (receive states)
VDC = 0 mV (otherwise)
DC level at pins RFP/RFN for various transceiver states
AC coupling is required if an antenna with a DC path to ground is used.
Serial capacitance and capacitance of each pin to ground must be < 30 pF.
XTAL1/ XTAL2
VDC = 0.9V at both pins
CPAR = 3 pF
DC level at pins XTAL1/XTAL2 for various transceiver states
Parasitic capacitance (CPAR) of the pins must be considered as additional
load capacitance to the crystal.
DVDD
VDC = 1.8V (all states, except SLEEP)
VDC = 0 mV (otherwise)
DC level at pin DVDD for various transceiver states
Supply pins (voltage regulator output) for the digital 1.8V voltage domain,
recommended bypass capacitor 1 µF.
AVDD
VDC = 1.8V (all states, except P_ON,
SLEEP, RESET, and TRX_OFF)
VDC = 0 mV (otherwise)
DC level at pin AVDD for various transceiver states
Supply pin (voltage regulator output) for the analog 1.8V voltage domain,
recommended bypass capacitor 1 µF.
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1.3
Digital Pins
The AT86RF231 provides a digital microcontroller interface. The interface comprises a slave
SPI (/SEL, SCLK, MOSI and MISO) and additional control signals (CLKM, IRQ, SLP_TR, /RST
and DIG2). The microcontroller interface is described in detail in Section 6. “Microcontroller
Interface” on page 16.
Additional digital output signals DIG1...DIG4 are provided to control external blocks, i.e. for
Antenna Diversity RF switch control or as an RX/TX Indicator, see Section 11.4 “Antenna Diversity” on page 142 and Section 11.5 “RX/TX Indicator” on page 147. After reset, these pins are
pulled-down to digital ground (DIG1/DIG2) or analog ground (DIG3/DIG4).
1.3.1
Table 1-3.
Driver Strength Settings
The driver strength of all digital output pins (MISO, IRQ, DIG1, DIG2, DIG3, DIG4) and CLKM
pin can be configured using register 0x03 (TRX_CTRL_0), see Table 1-3 on page 7.
Digital Output Driver Configuration
Pins
Default Driver Strength
Recommendation/Comment
MISO, IRQ, DIG1,..., DIG4
2 mA
Adjustable to 2 mA, 4 mA, 6 mA and 8 mA
CLKM
4 mA
Adjustable to 2 mA, 4 mA, 6 mA and 8 mA
The capacitive load should be as small as possible as, not larger than 50 pF when using the
2 mA minimum driver strength setting. Generally, the output driver strength should be adjusted
to the lowest possible value in order to keep the current consumption and the emission of digital
signal harmonics low.
1.3.2
Pull-Up and Pull-Down Configuration
All digital input pins are internally pulled-up or pulled-down in radio transceiver state P_ON, see
Section 7.1.2.1 “P_ON - Power-On after VDD” on page 34. Table 1-4 on page 7 summarizes the
pull-up and pull-down configuration.
Table 1-4.
Pull-Up / Pull-Down Configuration of Digital Input Pins in P_ON State
Pins
H =ˆ pull-up, L =ˆ pull-down
/RST
H
/SEL
H
SCLK
L
MOSI
L
SLP_TR
L
In all other radio transceiver states, no pull-up or pull-down circuitry is connected to any of the
digital input pins mentioned in Table 1-4 on page 7. In RESET state, the pull-up / pull-down configuration is disabled.
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1.3.3
Register Description
Register 0x03 (TRX_CTRL_0):
The TRX_CTRL_0 register controls the drive current of the digital output pads and the CLKM
clock rate.
Bit
7
0x03
6
5
PAD_IO
4
PAD_IO_CLKM
3
2
CLKM_SHA_SEL
1
0
CLKM_CTRL
TRX_CTRL_0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
1
1
0
0
1
• Bit [7:6] - PAD_IO
The register bits set the output driver current of all digital output pads, except CLKM.
Table 1-5.
Digital Output Driver Strength
Register Bit
Value
PAD_IO
Note:
Description
0(1)
2 mA
1
4 mA
2
6 mA
3
8 mA
1. Reset values of register bits are underlined characterized in the document.
• Bit [5:4] - PAD_IO_CLKM
The register bits set the output driver current of pin CLKM. Refer also to Section 9.6 “Crystal
Oscillator (XOSC)” on page 116.
Table 1-6.
CLKM Driver Strength
Register Bit
PAD_IO_CLKM
Value
Description
0
2 mA
1
4 mA
2
6 mA
3
8 mA
• Bit 3 - CLKM_SHA_SEL
Refer to Section 9.6 “Crystal Oscillator (XOSC)” on page 116.
• Bit [2:0] - CLKM_CTRL
Refer to Section 9.6 “Crystal Oscillator (XOSC)” on page 116.
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2. Disclaimer
Typical values contained in this datasheet are based on simulations and testing. Min and Max
values are available when the radio transceiver has been fully characterized.
3. Overview
The AT86RF231 is a feature rich, low-power 2.4 GHz radio transceiver designed for industrial
and consumer ZigBee/IEEE 802.15.4, 6LoWPAN, RF4CE and high data rate 2.4 GHz ISM band
applications. The radio transceiver is a true SPI-to-antenna solution. All RF-critical components
except the antenna, crystal and de-coupling capacitors are integrated on-chip. Therefore, the
AT86RF231 is particularly suitable for applications like:
• 2.4 GHz IEEE 802.15.4 and ZigBee systems
• 6LoWPAN and RF4CE systems
• Wireless sensor networks
• Industrial control, sensing and automation (SP100, WirelessHART)
• Residential and commercial automation
• Health care
• Consumer electronics
• PC peripherals
The AT86RF231 can be operated by using an external microcontroller like Atmel's AVR microcontrollers. A comprehensive software programming description can be found in reference [6],
AT86RF231 Software Programming Model.
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4. General Circuit Description
This single-chip radio transceiver provides a complete radio transceiver interface between an
antenna and a microcontroller. It comprises the analog radio, digital modulation and demodulation including time and frequency synchronization and data buffering. The number of external
components is minimized such that only the antenna, the crystal and decoupling capacitors are
required. The bidirectional differential antenna pins (RFP, RFN) are used for transmission and
reception, thus no external antenna switch is needed.
The AT86RF231 block diagram is shown in Figure 4-1 on page 10.
ext. PA and Power
Control
DIG3/4
PA
XTAL2
AT86RF231 Block Diagram
XTAL1
Figure 4-1.
XOSC
PLL
AVREG
TX Data
Configuration Registers
TX BBP
/SEL
DVREG
SPI
(Slave)
RFP
FTN, BATMON
Frame
Buffer
MISO
MOSI
SCLK
RFN
LNA
PPF
BPF
Limiter
ADC
RX BBP
AES
IRQ
CLKM
DIG2
AGC
AD
DIG1/2
Analog Domain
/RST
RSSI
Control Logic
SLP_TR
Antenna Diversity
Digital Domain
The received RF signal at pins RFN and RFP is differentially fed through the low-noise amplifier
(LNA) to the RF filter (PPF) to generate a complex signal, driving the integrated channel filter
(BPF). The limiting amplifier provides sufficient gain to drive the succeeding analog-to-digital
converter (ADC) and generates a digital RSSI signal. The ADC output signal is sampled by the
digital base band receiver (RX BBP).
The transmit modulation scheme is offset-QPSK (O-QPSK) with half-sine pulse shaping and 32length block coding (spreading) according to [1] and [2]. The modulation signal is generated in
the digital transmitter (TX BBP) and applied to the fractional-N frequency synthesis (PLL), to
ensure the coherent phase modulation required for demodulation of O-QPSK signals. The frequency-modulated signal is fed to the power amplifier (PA).
A differential pin pair DIG3/DIG4 can be enabled to control an external RF front-end.
Two on-chip low-dropout voltage regulators (A|DVREG) provide the analog and digital 1.8V
supply.
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An internal 128-byte RAM for RX and TX (Frame Buffer) buffers the data to be transmitted or the
received data.
The configuration of the AT86RF231, reading and writing of Frame Buffer is controlled by the
SPI interface and additional control lines.
The AT86RF231 further contains comprehensive hardware-MAC support (Extended Operating
Mode) and a security engine (AES) to improve the overall system power efficiency and timing.
The stand-alone 128-bit AES engine can be accessed in parallel to all PHY operational transactions and states using the SPI interface, except during SLEEP state.
For applications not necessarily targeting IEEE 802.15.4 compliant networks, the radio transceiver also supports alternative data rates up to 2 Mb/s.
For long-range applications or to improve the reliability of an RF connection the RF performance
can further be improved by using an external RF front-end or Antenna Diversity. Both operation
modes are supported by the AT86RF231 with dedicated control pins without the interaction of
the microcontroller.
Additional features of the Extended Feature Set, see Section 11. “AT86RF231 Extended Feature Set” on page 128, are provided to simplify the interaction between radio transceiver and
microcontroller.
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5. Application Circuits
5.1
Basic Application Schematic
A basic application schematic of the AT86RF231 with a single-ended RF connector is shown in
Figure 5-1 on page 12. The 50Ω single-ended RF input is transformed to the 100Ω differential
RF port impedance using balun B1. The capacitors C1 and C2 provide AC coupling of the RF
input to the RF port, optional capacitor C4 improves matching if required.
Figure 5-1.
Basic Application Schematic
CB2
CX1
XTAL
CX2
VDD
CB1
DVSS 21
AT86RF231
MISO 20
DVSS
CLKM 17
DEVDD
8 /RST
DVDD
DVSS 18
DVDD
7 DVSS
DVSS
SCLK 19
DIG2
6 AVSS
9
Digital Interface
XTAL2
XTAL1
AVSS
MOSI 22
DIG1
C2
EVDD
3 AVSS
5 RFN
C4
AVDD
/SEL 23
4 RFP
B1
IRQ 24
2 DIG4
SLP_TR
C1
RF
30 29 28 27 26 25
AVSS
1 DIG3
AVSS
AVSS
32 31
R1
C3
10 11 12 13 14 15 16
VDD
CB3
CB4
The power supply decoupling capacitors (CB2, CB4) are connected to the external analog supply pin (EVDD, pin 28) and external digital supply pin (DEVDD, pin 15). Capacitors CB1 and
CB3 are bypass capacitors for the integrated analog and digital voltage regulators to ensure stable operation. All decoupling and bypass capacitors should be placed as close as possible to the
pins and should have a low-resistance and low-inductance connection to ground to achieve the
best performance.
The crystal (XTAL), the two load capacitors (CX1, CX2), and the internal circuitry connected to
pins XTAL1 and XTAL2 form the crystal oscillator. To achieve the best accuracy and stability of
the reference frequency, large parasitic capacitances should be avoided. Crystal lines should be
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routed as short as possible and not in proximity of digital I/O signals. This is especially required
for the High Data Rate Modes, refer to Section 11.3 “High Data Rate Modes” on page 137.
Crosstalk from digital signals on the crystal pins or the RF pins can degrade the system performance. Therefore, a low-pass filter (C3, R1) is placed close to the CLKM output pin to reduce
the emission of CLKM signal harmonics. This is not needed if the CLKM pin is not used as a
microcontroller clock source. In that case, the output should be turned off during device
initialization.
The ground plane of the application board should be separated into four independent fragments,
the analog, the digital, the antenna and the XTAL ground plane. The exposed paddle shall act as
the reference point of the individual grounds.
Table 5-1.
Example Bill of Materials (BoM) for Basic Application Schematic
Designator
Description
Value
B1
SMD balun
SMD balun / filter
B1
(alternatively)
CB1
CB3
Manufacture
Part Number
Comment
2.45 GHz
Wuerth
748421245
2.45 GHz Balun
2.45 GHz
Johanson
Technology
2450FB15L0001
2.45 GHz Balun / Filter
1 µF
AVX
Murata
0603YD105KAT2A
GRM188R61C105KA12D
X5R
(0603)
10%
LDO VREG
bypass capacitor
CB2
CB4
Power Supply decoupling
CX1, CX2
Crystal load capacitor
12 pF
AVX
Murata
06035A120JA
GRP1886C1H120JA01
COG
(0603)
5%
22 pF
B37930
B37920
06035A220JAT2A
5%
RF coupling capacitor
Epcos
Epcos
AVX
COG
C1, C2
AVX
Murata
06035A229DA
GRP1886C1H2R0DA01
CLKM low-pass
filter capacitor
C3
2.2 pF
16V
50V
(0402 or 0603)
COG
(0603)
±0.5 pF
Designed for fCLKM=1 MHz
C4 (optional)
RF matching
R1
CLKM low-pass
filter resistor
XTAL
Crystal
Note:
Depends on final PCB
implementation
0.47 pF
Designed for fCLKM=1 MHz
680Ω
CX-4025 16 MHz
SX-4025 16 MHz
ACAL Taitjen
Siward
XWBBPL-F-1
A207-011
Please note that pins DIG1...4 are connected to the ground in the Basic Application Schematic, refer to Figure 5-1 on page 12.
Special programming of these pins require a different schematic, refer to “Extended Feature Set Application Schematic” on
page 14.
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5.2
Extended Feature Set Application Schematic
The AT86RF231 supports additional features like:
•
Security Module (AES)
see Section 11.1
•
High Data Rate Mode
see Section 11.3
•
Antenna Diversity
uses pins DIG1/2
see Section 11.4
•
RX/TX indicator
uses pins DIG3/4
see Section 11.5
•
RX Frame Time Stamp
uses pin DIG2
see Section 11.6
An extended feature set application schematic illustrating the use of the AT86RF231 Extended
Feature Set, see Section 11. “AT86RF231 Extended Feature Set” on page 128, is shown in Figure 5-2 on page 14. Although this example shows all additional hardware features combined, it
is possible to use all features separately or in various combinations.
Figure 5-2.
Extended Feature Application Schematic
CB2
CX1
XTAL
CX2
VDD
26
25
AVDD
EVDD
AVSS
XTAL1
XTAL2
4 RFP
DVSS 21
AT86RF231
5 RFN
MISO 20
8 /RST
CLKM 17
DVSS
DVSS 18
DEVDD
SCLK 19
7 DVSS
DVDD
6 AVSS
DVDD
B1
MOSI 22
DVSS
SW1
3 AVSS
SLP_TR
Balun
N1
/SEL 23
DIG2
PA
RFSwitch
RFSwitch
LNA
IRQ 24
2 DIG4
Digital Interface
27
AVSS
28
DIG1
ANT1
30 29
1 DIG3
N2
SW2
31
AVSS
ANT0
32
AVSS
CB1
9
10
11
12
13
14
15
16
R1
C3
VDD
CB3
CB4
In this example, a balun (B1) transforms the differential RF signal at the radio transceiver RF
pins (RFP/RFN) to a single ended RF signal, similar to the Basic Application Schematic; refer to
Figure 5-1 on page 12. The RF-Switches (SW1, SW2) separate between receive and transmit
path in an external RF front-end.
These switches are controlled by the RX/TX Indicator, represented by the differential pin pair
DIG3/DIG4, refer to Section 11.5 “RX/TX Indicator” on page 147.
During receive the radio transceiver searches for the most reliable RF signal path using the
Antenna Diversity algorithm. One antenna is selected (SW2) by the Antenna Diversity RF switch
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control pins DIG1/DIG2, the RF signal is amplified by an optional low-noise amplifier (N2) and
fed to the radio transceiver using the second RX/TX switch (SW1).
During transmit the AT86RF231 TX signal is amplified using an external PA (N1) and fed to the
antennas via an RF switch (SW2). In this example RF switch SW2 further supports Antenna
Diversity controlled by the differential pin pair DIG1/DIG2.
The security engine (AES) and High Data Rate Modes do not require specific circuitry to operate. The security engine (AES) has to be configured in advance, for details refer to Section 11.1
“Security Module (AES)” on page 128. The High Data Rate Modes are enabled by register bits
OQPSK_DATA_RATE (register 0x0C, TRX_CTRL_2), for details refer to Section 11.3 “High
Data Rate Modes” on page 137.
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AT86RF231
6. Microcontroller Interface
This section describes the AT86RF231 to microcontroller interface. The interface comprises a
slave SPI and additional control signals; see Figure 6-1 on page 16. The SPI timing and protocol
are described below.
Microcontroller to AT86RF231 Interface
SPI
AT86RF231
/SEL
/SEL
/SEL
MOSI
MOSI
MOSI
MISO
MISO
MISO
SCLK
SCLK
SCLK
GPIO1/CLK
CLKM
CLKM
GPIO2/IRQ
IRQ
SPI - Master
Microcontroller
SPI - Slave
Figure 6-1.
IRQ
SLP_TR
GPIO3
SLP_TR
GPIO4
/RST
/RST
GPIO5
DIG2
DIG2
Microcontrollers with a master SPI such as Atmel's AVR family interface directly to the
AT86RF231. The SPI is used for register, Frame Buffer, SRAM and AES access. The additional
control signals are connected to the GPIO/IRQ interface of the microcontroller.
Table 6-1 on page 16 introduces the radio transceiver I/O signals and their functionality.
Table 6-1.
Signal Description of Microcontroller Interface
Signal
Description
/SEL
SPI select signal, active low
MOSI
SPI data (master output slave input) signal
MISO
SPI data (master input slave output) signal
SCLK
SPI clock signal
CLKM
Clock output, refer to Section 9.6.4 usable as:
-microcontroller clock source
-high precision timing reference
-MAC timer reference
IRQ
Interrupt request signal, further used as:
-Frame Buffer Empty Indicator, refer to Section 11.7
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Table 6-1.
6.1
Signal Description of Microcontroller Interface (Continued)
SLP_TR
Multipurpose control signal (functionality is state dependent, see Section 6.5):
-Sleep/Wakeup
enable/disable SLEEP state
-TX start
BUSY_TX_(ARET) state
-disable/enable CLKM
RX_(AACK)_ON state
/RST
AT86RF231 reset signal, active low
DIG2
Optional, IRQ_2 (RX_START) for RX Frame Time Stamping, see Section 11.6
SPI Timing Description
Pin 17 (CLKM) can be used as a microcontroller master clock source. If the microcontroller
derives the SPI master clock (SCLK) directly from CLKM, the SPI operates in synchronous
mode, otherwise in asynchronous mode.
In synchronous mode, the maximum SCLK frequency is 8 MHz.
In asynchronous mode, the maximum SCLK frequency is limited to 7.5 MHz. The signal at pin
CLKM is not required to derive SCLK and may be disabled to reduce power consumption and
spurious emissions.
Figure 6-2 on page 17 and Figure 6-3 on page 17 illustrate the SPI timing and introduces its
parameters. The corresponding timing parameter definitions t1 - t9 are defined in Section 12.4
“Digital Interface Timing Characteristics” on page 157.
Figure 6-2.
SPI Timing, Global Map and Definition of Timing Parameters t5, t6, t8 and t9
t8
t9
/SEL
SCLK
MOSI
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
t5
MISO
Figure 6-3.
Bit 7
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
t6
Bit 7
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
SPI Timing, Detailed Drawing of Timing Parameter t1 to t4
/SEL
SCLK
t3
MOSI
t4
Bit 7
Bit 6
t1
MISO
Bit 5
t2
Bit 7
Bit 6
Bit 5
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The SPI is based on a byte-oriented protocol and is always a bidirectional communication
between master and slave. The SPI master starts the transfer by asserting /SEL = L. Then the
master generates eight SPI clock cycles to transfer one byte to the radio transceiver (via MOSI).
At the same time, the slave transmits one byte to the master (via MISO). When the master wants
to receive one byte of data from the slave it must also transmit one byte to the slave. All bytes
are transferred with MSB first. An SPI transaction is finished by releasing /SEL = H.
An SPI register access consists of two bytes, a Frame Buffer or SRAM access of at least two or
more bytes as described in Section 6.2 “SPI Protocol” on page 19.
/SEL = L enables the MISO output driver of the AT86RF231. The MSB of MISO is valid after t1
(see Section 12.4 “Digital Interface Timing Characteristics” on page 157 parameter 12.4.3) and
is updated at each falling edge of SCLK. If the driver is disabled, there is no internal pull-up circuitry connected to it. Driving the appropriate signal level must be ensured by the master device
or an external pull-up resistor. Note, when both /SEL and /RST are active, the MISO output
driver is also enabled.
Referring to Figure 6-2 on page 17 and Figure 6-3 on page 17 MOSI is sampled at the rising
edge of the SCLK signal and the output is set at the falling edge of SCLK. The signal must be
stable before and after the rising edge of SCLK as specified by t3 and t4, refer to Section 12.4
“Digital Interface Timing Characteristics” on page 157 parameters 12.4.5 and 12.4.6.
This SPI operational mode is commonly known as "SPI mode 0".
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6.2
SPI Protocol
Each SPI sequence starts with transferring a command byte from the SPI master via MOSI (see
Table 6-2 on page 19) with MSB first. This command byte defines the SPI access mode and
additional mode-dependent information.
Table 6-2.
SPI Command Byte definition
Bit 7
Bit 6
1
0
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access Mode
Access Type
Register address [5:0]
Read access
Register access
1
1
0
0
Register address [5:0]
1
Write access
Reserved
Read access
Frame Buffer access
0
1
1
Reserved
0
0
0
Reserved
Write access
Read access
SRAM access
0
1
0
Reserved
Write access
Each SPI transfer returns bytes back to the SPI master on MISO. The content of the first byte
(see value "PHY_STATUS" in Figure 6-4 on page 19 to Figure 6-14 on page 23) is set to zero
after reset. To transfer status information of the radio transceiver to the microcontroller, the content of the first byte can be configured with register bits SPI_CMD_MODE (register 0x04,
TRX_CTRL_1). For details, refer to Section 6.3.1 “Register Description - SPI Control” on page
24.
In Figure 6-4 on page 19 to Figure 6-14 on page 23 and the following chapters logic values
stated with XX on MOSI are ignored by the radio transceiver, but need to have a valid logic level.
Return values on MISO stated as XX shall be ignored by the microcontroller.
The different access modes are described within the following sections.
6.2.1
Register Access Mode
A register access mode is a two-byte read/write operation initiated by /SEL = L. The first transferred byte on MOSI is the command byte including an identifier bit (bit7 = 1), a read/write select
bit (bit 6), and a 6-bit register address.
On read access, the content of the selected register address is returned in the second byte on
MISO (see Figure 6-4 on page 19).
Figure 6-4.
Packet Structure - Register Read Access
byte 1 (command byte)
MOSI
MISO
Note:
1
0
ADDRESS[5:0]
PHY_STATUS(1)
byte 2 (data byte)
XX
READ DATA[7:0]
1. Each SPI access can be configured to return radio controller status information
(PHY_STATUS) on MISO, for details refer to Section 6.3 “Radio Transceiver Status information” on page 24.
On write access, the second byte transferred on MOSI contains the write data to the selected
address (see Figure 6-5 on page 20).
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Figure 6-5.
Packet Structure - Register Write Access
byte 1 (command byte)
MOSI
1
1
MISO
ADDRESS[5:0]
byte 2 (data byte)
WRITE DATA[7:0]
PHY_STATUS
XX
Each register access must be terminated by setting /SEL = H.
Figure 6-6 on page 20 illustrates a typical SPI sequence for a register access sequence for write
and read respectively.
Figure 6-6.
Example SPI Sequence - Register Access Mode
Register Write Access
Register Read Access
/SEL
SCLK
MOSI
WRITE COMMAND
MISO
PHY_STATUS
6.2.2
WRITE DATA
READ COMMAND
XX
XX
PHY_STATUS
READ DATA
Frame Buffer Access Mode
The 128-byte Frame Buffer can hold the PHY service data unit (PSDU) data of one
IEEE 802.15.4 compliant RX or one TX frame of maximum length at a time. A detailed description of the Frame Buffer can be found in Section 9.3 “Frame Buffer” on page 107. An introduction
to the IEEE 802.15.4 frame format can be found in Section 8.1 “Introduction - IEEE 802.15.4 2006 Frame Format” on page 79.
Frame Buffer read and write accesses are used to read or write frame data (PSDU and additional information) from or to the Frame Buffer. Each access starts with /SEL = L followed by a
command byte on MOSI. If this byte indicates a frame read or write access, the next byte
PHR[7:0] indicates the frame length followed by the PSDU data, see Figure 6-7 on page 20 and
Figure 6-8 on page 21.
On Frame Buffer read access, PHY header (PHR) and PSDU are transferred via MISO starting
with the second byte. After the PSDU data, one more byte is transferred containing the link quality indication (LQI) value of the received frame, for details refer to Section 8.6 “Link Quality
Indication (LQI)” on page 99. Figure 6-7 on page 20 illustrates the packet structure of a Frame
Buffer read access.
Figure 6-7.
Packet Structure - Frame Read Access
byte 1 (command byte)
byte 2 (data byte)
byte 3 (data byte)
byte n-1 (data byte)
byte n (data byte)
MOSI
0 0 1 reserved[4:0]
XX
XX
XX
XX
MISO
PHY_STATUS
PHR[7:0]
PSDU[7:0]
PSDU[7:0]
LQI[7:0]
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Note, the Frame Buffer read access can be terminated at any time without any consequences by
setting /SEL = H, e.g. after reading the PHR byte only.
On Frame Buffer write access the second byte transferred on MOSI contains the frame length
(PHR field) followed by the payload data (PSDU) as shown by Figure 6-8 on page 21.
Figure 6-8.
Packet Structure - Frame Write Access
byte 1 (command byte)
byte 2 (data byte)
byte 3 (data byte)
byte n-1 (data byte)
byte n (data byte)
MOSI
0 1 1 reserved[4:0]
PHR[7:0]
PSDU[7:0]
PSDU[7:0]
PSDU[7:0]
MISO
PHY_STATUS
XX
XX
XX
XX
The number of bytes n for one frame access is calculated as follows:
• Read Access:
n = 3 + frame_length
[PHY_STATUS, PHR byte, PSDU data, and LQI byte]
• Write Access:
n = 2 + frame_length
[command byte, PHR byte, and PSDU data]
The maximum value of frame_length is 127 bytes. That means that n ≤ 130 for Frame Buffer
read and n ≤ 129 for Frame Buffer write accesses.
Each read or write of a data byte increments automatically the address counter of the Frame
Buffer until the access is terminated by setting /SEL = H. A Frame Buffer read access may be
terminated (/SEL = H) at any time without affecting the Frame Buffer content. Another Frame
Buffer read operation starts again at the PHR field.
The content of the Frame Buffer is only overwritten by a new received frame or a Frame Buffer
write access.
Figure 6-9 on page 21 and Figure 6-10 on page 22 illustrate an example SPI sequence of a
Frame Buffer access to read and write a frame with 4-byte PSDU respectively.
Figure 6-9.
Example SPI Sequence - Frame Buffer Read of a Frame with 4-byte PSDU
/SEL
SCLK
MOSI
COMMAND
XX
MISO
PHY_STATUS
PHR
XX
PSDU 1
XX
PSDU 2
XX
PSDU 3
XX
PSDU 4
XX
LQI
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Figure 6-10. Example SPI Sequence - Frame Buffer Write of a Frame with 4 byte PSDU
/SEL
SCLK
MOSI
COMMAND
MISO
PHY_STATUS
PHR
PSDU 1
XX
XX
PSDU 2
XX
PSDU 3
PSDU 4
XX
XX
Access violations during a Frame Buffer read or write access are indicated by interrupt IRQ_6
(TRX_UR). For further details, refer to Section 9.3 “Frame Buffer” on page 107.
Notes
• The Frame Buffer is shared between RX and TX; therefore, the frame data are overwritten by
new incoming frames. If the TX frame data are to be retransmitted, it must be ensured that no
frame was received in the meanwhile.
• To avoid overwriting during receive Dynamic Frame Buffer Protection can be enabled, refer to
Section 11.8 “Dynamic Frame Buffer Protection” on page 154.
• It is not possible to retransmit received frames without a Frame Buffer read and write access
cycle.
• For exceptions, e.g. receiving acknowledgement frames in Extended Operating Mode
(TX_ARET) refer to Section 7.2.4 “TX_ARET_ON - Transmit with Automatic Retry and
CSMA-CA Retry” on page 64.
6.2.3
SRAM Access Mode
The SRAM access mode allows accessing dedicated bytes within the Frame Buffer. This may
reduce the SPI traffic.
The SRAM access mode is useful, for instance, if a transmit frame is already stored in the Frame
Buffer and dedicated bytes (e.g. sequence number, address field) need to be replaced before
retransmitting the frame. Furthermore, it can be used to access only the LQI value after frame
reception. A detailed description of the user accessible frame content can be found in Section
9.3 “Frame Buffer” on page 107.
Each SRAM access starts with /SEL = L. The first transferred byte on MOSI shall be the command byte and must indicate an SRAM access mode according to the definition in Table 6-2 on
page 19. The following byte indicates the start address of the write or read access. The address
space is 0x00 to 0x7F for radio transceiver receive or transmit operations.
On SRAM read access, one or more bytes of read data are transferred on MISO starting with the
third byte of the access sequence (see Figure 6-11 on page 22).
Figure 6-11. Packet Structure - SRAM Read Access
byte 1 (command byte)
MOSI
MISO
0 0 0 reserved[4:0] 0
PHY_STATUS
byte 2 (address)
ADDRESS[6:0]
XX
byte 3 (data byte)
byte n-1 (data byte)
byte n (data byte)
XX
XX
XX
DATA[7:0]
DATA[7:0]
DATA[7:0]
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On SRAM write access, one or more bytes of write data are transferred on MOSI starting with
the third byte of the access sequence (see Figure 6-12 on page 23).
On SRAM read or write accesses do not attempt to read or write bytes beyond the SRAM buffer
size.
Figure 6-12. Packet Structure - SRAM Write Access
byte 1 (command byte)
MOSI
MISO
byte 2 (address)
0 1 0 reserved[4:0] 0
ADDRESS[6:0]
PHY_STATUS
XX
byte 3 (data byte)
byte n-1 (data byte)
byte n (data byte)
DATA[7:0]
DATA[7:0]
DATA[7:0]
XX
XX
XX
As long as /SEL = L, every subsequent byte read or byte write increments the address counter
of the Frame Buffer until the SRAM access is terminated by /SEL = H.
Figure 6-13 on page 23 and Figure 6-14 on page 23 illustrate an example SPI sequence of a
SRAM access to read and write a data package of 5-byte length respectively.
Figure 6-13. Example SPI Sequence - SRAM Read Access of a 5 byte Data Package
/SEL
SCLK
MOSI
COMMAND
MISO
PHY_STATUS
ADDRESS
XX
XX
DATA 1
XX
DATA 2
XX
DATA 3
XX
XX
DATA 4
DATA 5
DATA 4
DATA 5
Figure 6-14. Example SPI Sequence - SRAM Write Access of a 5 byte Data Package
/SEL
SCLK
MOSI
COMMAND
MISO
PHY_STATUS
ADDRESS
XX
DATA 1
XX
DATA 2
XX
DATA 3
XX
XX
XX
Notes
• The SRAM access mode is not intended to be used as an alternative to the Frame Buffer
access modes (see Section 6.2.2 “Frame Buffer Access Mode” on page 20).
• If the SRAM access mode is used to read PSDU data, the Frame Buffer contains all PSDU
data except the frame length byte (PHR). The frame length information can be accessed only
using Frame Buffer access.
• Frame Buffer access violations are not indicated by a TRX_UR interrupt when using the
SRAM access mode, for further details refer to Section 9.3.3 “Interrupt Handling” on page
109.
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6.3
Radio Transceiver Status information
Each SPI access can be configured to return status information of the radio transceiver
(PHY_STATUS) to the microcontroller using the first byte of the data transferred via MISO.
The content of the radio transceiver status information can be configured using register bits
SPI_CMD_MODE (register 0x04, TRX_CTRL_1). After reset, the content on the first byte send
on MISO to the microcontroller is set to 0x00.
6.3.1
Register Description - SPI Control
Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
1
0
0
+0x04
3
2
1
0
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
0
0
0
SPI_CMD_MODE
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
Refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
Refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Each SPI transfer returns bytes back to the SPI master. The content of the first byte can be configured using register bits SPI_CMD_MODE. The transfer of the following status information can
be configured as follows:
Table 6-3.
Radio Transceiver Status Information - PHY_STATUS
Register Bit
SPI_CMD_MODE
Value
Description
0
default (empty, all bits 0x00)
1
monitor TRX_STATUS register; see Section 7.1.5
2
monitor PHY_RSSI register; see Section 8.3
3
monitor IRQ_STATUS register; see Section 6.6
• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
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6.4
Radio Transceiver Identification
The AT86RF231 can be identified by four registers. One register contains a unique part number
and one register the corresponding version number. Two additional registers contain the JEDEC
manufacture ID.
6.4.1
Register Description - AT86RF231 Identification
Register 0x1C (PART_NUM):
Bit
7
6
5
4
+0x1C
3
2
1
0
PART_NUM[7:0]
PART_NUM
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
1
1
• Bit [7:0] - PART_NUM
This register contains the radio transceiver part number.
Table 6-4.
Radio Transceiver Part Number
Register Bit
Value
PART_NUM
3
Description
AT86RF231 part number
Register 0x1D (VERSION_NUM):
Bit
7
6
5
Read/Write
R
R
R
R
Reset Value
0
0
0
0
+0x1D
4
3
2
1
0
R
R
R
R
0
0
1
0
2
1
0
VERSION_NUM[7:0]
VERSION_NUM
• Bit [7:0] - VERSION_NUM
This register contains the radio transceiver version number.
Table 6-5.
Radio Transceiver Version Number
Register Bit
Value
VERSION_NUM
Description
Revision A
2
Register 0x1E (MAN_ID_0):
Bit
7
6
5
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
1
1
1
1
1
+0x1E
4
3
MAN_ID_0[7:0]
MAN_ID_O
• Bit [7:0] - MAN_ID_0
Bits [7:0] of the 32-bit JEDEC manufacturer ID are stored in register bits MAN_ID_0. Bits [15:8]
are stored in register 0x1F (MAN_ID_1). The highest 16 bits of the ID are not stored in registers.
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Table 6-6.
JEDEC Manufacturer ID - Bits [7:0]
Register Bit
Value
Description
MAN_ID_0
0x1F
Atmel JEDEC manufacturer ID,
Bits [7:0] of 32 bit manufacturer ID: 00 00 00 1F
Register 0x1F (MAN_ID_1):
Bit
7
6
5
Read/Write
R
R
R
R
Reset Value
0
0
0
0
+0x1F
4
3
2
1
0
R
R
R
R
0
0
0
0
MAN_ID_1[7:0]
MAN_ID_1
• Bit [7:0] - MAN_ID_1
Bits [15:8] of the 32-bit JEDEC manufacturer ID are stored in register bits MAN_ID_1. Bits [7:0]
are stored in register 0x1E (MAN_ID_0). The higher 16 bits of the ID are not stored in registers.
Table 6-7.
JEDEC Manufacturer ID - Bits [15:8]
Register Bit
Value
Description
MAN_ID_1
0x00
Atmel JEDEC manufacturer ID,
Bits [15:8] of 32 bit manufacturer ID: 00 00 00 1F
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6.5
Sleep/Wake-up and Transmit Signal (SLP_TR)
Pin 11 (SLP_TR) is a multi-functional pin. Its function relates to the current state of the
AT86RF231 and is summarized in Table 6-8 on page 27. The radio transceiver states are
explained in detail Section 7. “Operating Modes” on page 33.
Table 6-8.
SLP_TR Multi-functional Pin
Transceiver Status
Function
Transition
Description
PLL_ON
TX start
L⇒H
Starts frame transmission
TX_ARET_ON
TX start
L⇒H
Starts TX_ARET transaction
TRX_OFF
Sleep
L⇒H
Takes the radio transceiver into SLEEP state, CLKM disabled
SLEEP
Wakeup
H⇒L
Takes the radio transceiver back into TRX_OFF state, level sensitive
RX_ON
Disable CLKM
L⇒H
Takes the radio transceiver into RX_ON_NOCLK state and disables CLKM
RX_ON_NOCLK
Enable CLKM
H⇒L
Takes the radio transceiver into RX_ON state and enables CLKM
RX_AACK_ON
Disable CLKM
L⇒H
Takes the radio transceiver into RX_AACK_ON_NOCLK state and disables
CLKM
RX_AACK_ON_NOCLK
Enable CLKM
H⇒L
Takes the radio transceiver into RX_AACK_ON state and enables CLKM
In states PLL_ON and TX_ARET_ON, pin SLP_TR is used as trigger input to initiate a TX transaction. Here pin SLP_TR is sensitive on rising edge only.
After initiating a state change by a rising edge at pin SLP_TR in radio transceiver states
TRX_OFF, RX_ON or RX_AACK_ON, the radio transceiver remains in the new state as long as
the pin is logical high and returns to the preceding state with the falling edge.
SLEEP state
The SLEEP state is used when radio transceiver functionality is not required, and thus the
AT86RF231 can be powered down to reduce the overall power consumption.
A power-down scenario is shown in Figure 6-15 on page 28. When the radio transceiver is in
TRX_OFF state the microcontroller forces the AT86RF231 to SLEEP by setting SLP_TR = H. If
pin 17 (CLKM) provides a clock to the microcontroller this clock is switched off after 35 clock
cycles. This enables a microcontroller in a synchronous system to complete its power-down routine and prevent deadlock situations. The AT86RF231 awakes when the microcontroller
releases pin SLP_TR. This concept provides the lowest possible power consumption.
The CLKM clock frequency settings for 250 kHz and 62.5 kHz are not intended to directly clock
the microcontroller. When using these clock rates, CLKM is turned off immediately when entering SLEEP state.
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Figure 6-15. Sleep and Wake-up Initiated by Asynchronous Microcontroller Timer
SLP_TR
tTR15
CLKM
35 CLKM clock cycles
CLKM off
async timer elapses
(microcontroller)
Note: Timing figure tTR15 refer to section Table 7-1 on page 42.
RX_ON and RX_AACK_ON states
For synchronous systems, where CLKM is used as a microcontroller clock source and the SPI
master clock (SCLK) is directly derived from CLKM, the AT86RF231 supports an additional
power-down mode for receive operating states (RX_ON and RX_AACK_ON).
If an incoming frame is expected and no other applications are running on the microcontroller, it
can be powered down without missing incoming frames.
This can be achieved by a rising edge on pin SLP_TR that turns off the CLKM. Then the radio
transceiver state changes from RX_ON or RX_AACK_ON (Extended Operating Mode) to
RX_ON_NOCLK or RX_AACK_ON_NOCLK respectively.
In case that a frame is received (e.g. indicated by an IRQ_2 (RX_START) interrupt) the clock
output CLKM is automatically switched on again.
This scenario is shown in Figure 6-16 on page 28. In RX_ON state, the clock at pin 17 (CLKM) is
switched off after 35 clock cycles when setting the pin SLP_TR = H.
The CLKM clock frequency settings for 250 kHz and 62.5 kHz are not intended to directly clock
the microcontroller. When using these clock rates, CLKM is turned off immediately when entering RX_ON_NOCLK and RX_AACK_ON_NOCLK respectively.
In states RX_(AACK)_ON_NOCLK and RX_(AACK)_ON, the radio transceiver current consumptions are equivalent. However, the RX_(AACK)_ON_NOCLK current consumption is
reduced by the current required for driving pin 17 (CLKM).
Figure 6-16. Wake-Up Initiated by Radio Transceiver Interrupt
radio transceiver
IRQ issued
IRQ
typ. 5 µs
SLP_TR
CLKM
35 CLKM clock cycles
CLKM off
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6.6
Interrupt Logic
6.6.1
Overview
The AT86RF231 differentiates between nine interrupt events (eight physical interrupt registers,
one shared by two functions). Each interrupt is enabled by setting the corresponding bit in the
interrupt mask register 0x0E (IRQ_MASK). Internally, each pending interrupt is stored in a separate bit of the interrupt status register. All interrupt events are OR-combined to a single external
interrupt signal (IRQ, pin 24). If an interrupt is issued (pin IRQ = H), the microcontroller shall read
the interrupt status register 0x0F (IRQ_STATUS) to determine the source of the interrupt. A read
access to this register clears the interrupt status register and thus the IRQ pin, too.
Interrupts are not cleared automatically when the event that caused them vanishes. Exceptions
are IRQ_0 (PLL_LOCK) and IRQ_1 (PLL_UNLOCK) because the occurrence of one clears the
other.
The supported interrupts for the Basic Operating Mode are summarized in Table 6-9 on page
29.
Table 6-9.
Interrupt Description in Basic Operating Mode
IRQ Name
Description
IRQ_7 (BAT_LOW)
Indicates a supply voltage below the programmed threshold.
9.5.4
IRQ_6 (TRX_UR)
Indicates a Frame Buffer access violation.
9.3.3
IRQ_5 (AMI)
Indicates address matching.
IRQ_4 (CCA_ED_DONE)
Multi-functional interrupt:
1. AWAKE_END:
• Indicates radio transceiver reached TRX_OFF state after P_ON, RESET, or SLEEP states.
2. CCA_ED_DONE:
Section
7.2.3.5
7.1.2.3
• Indicates the end of a CCA or ED measurement.
8.4.4
8.5.4
IRQ_3 (TRX_END)
RX: Indicates the completion of a frame reception.
TX: Indicates the completion of a frame transmission.
7.1.3
7.1.3
IRQ_2 (RX_START)
Indicates the start of a PSDU reception. The TRX_STATE changes to BUSY_RX, the PHR is
valid to read from Frame Buffer.
7.1.3
IRQ_1 (PLL_UNLOCK)
Indicates PLL unlock. If the radio transceiver is BUSY_TX / BUSY_TX_ARET state, the PA is
turned off immediately.
9.7.5
IRQ_0 (PLL_LOCK)
Indicates PLL lock.
9.7.5
The interrupt IRQ_4 has two meanings, depending on the current radio transceiver state, refer to
register 0x01 (TRX_STATUS).
After P_ON, SLEEP, or RESET, the radio transceiver issues an interrupt IRQ_4 (AWAKE_END)
when it enters state TRX_OFF.
The second meaning is only valid for receive states. If the microcontroller initiates an energydetect (ED) or clear-channel-assessment (CCA) measurement, the completion of the measurement is indicated by interrupt IRQ_4 (CCA_ED_DONE), refer to Section 8.4.4 “Interrupt
Handling” on page 92 and Section 8.5.4 “Interrupt Handling” on page 95 for details.
After P_ON or RESET all interrupts are disabled. During radio transceiver initialization it is recommended to enable IRQ_4 (AWAKE_END) to be notified once the TRX_OFF state is entered.
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Note that AWAKE_END interrupt can usually not be seen when the transceiver enters
TRX_OFF state after RESET, because register 0x0E (IRQ_MASK) is reset to mask all interrupts. In this case, state TRX_OFF is normally entered before the microcontroller could modify
the register.
The interrupt handling in Extended Operating Mode is described in Section 7.2.5 “Interrupt Handling” on page 67.
If register bit IRQ_MASK_MODE (register 0x04, TRX_CTRL_1) is set, an interrupt event can be
read from IRQ_STATUS register even if the interrupt itself is masked. However, in that case no
timing information for this interrupt is provided.
The IRQ pin polarity can be configured with register bit IRQ_POLARITY (register 0x04,
TRX_CTRL_1). The default behavior is active high, which means that pin IRQ = H issues an
interrupt request.
If "Frame Buffer Empty Indicator" is enabled during Frame Buffer read access the IRQ pin has
an alternative functionality, refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152 for
details.
6.6.2
Register Description
Register 0x0E (IRQ_MASK):
The IRQ_MASK register is used to enable or disable individual interrupts. An interrupt is enabled
if the corresponding bit is set to 1. All interrupts are disabled after power up sequence (P_ON
state) or reset (RESET state).
Bit
7
6
5
4
3
2
1
0
MASK_BAT_LOW
MASK_TRX_UR
MASK_AMI
MASK_CCA_ED_DONE
MASK_TRX_END
MASK_RX_START
MASK_PLL_UNLOCK
MASK_PLL_LOCK
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
+0x0E
IRQ_MASK
If an interrupt is enabled it is recommended to read the interrupt status register 0x0F
(IRQ_STATUS) first to clear the history.
Register 0x0F (IRQ_STATUS):
The IRQ_STATUS register contains the status of the pending interrupt requests.
Bit
7
6
5
4
3
2
1
0
BAT_LOW
TRX_UR
AMI
CCA_ED_DONE
TRX_END
RX_START
PLL_UNLOCK
PLL_LOCK
Read/Write
R
R
R
R
R
R
R
R
Initial Value
0
0
0
0
0
0
0
0
+0x0F
IRQ_STATUS
By reading the register after an interrupt is signaled at pin 24 (IRQ) the source of the issued
interrupt can be identified. A read access to this register resets all interrupt bits, and so clears
the IRQ_STATUS register.
If register bit IRQ_MASK_MODE (register 0x04, TRX_CTRL_1) is set, an interrupt event can be
read from IRQ_STATUS register even if the interrupt itself is masked. However in that case no
timing information for this interrupt is provided.
If register bit IRQ_MASK_MODE is set, it is recommended to read the interrupt status register
0x0F (IRQ_STATUS) first to clear the history.
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Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
+0x04
3
2
1
0
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
0
0
0
SPI_CMD_MODE
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
The timing of a received frame can be determined by a separate pin. If register bit
IRQ_2_EXT_EN is set to 1, the reception of a PHR is directly issued on pin 10 (DIG2), similar to
interrupt IRQ_2 (RX_START). Note that this pin is also active even if the corresponding interrupt
event IRQ_2 (RX_START) mask bit in register 0x0E (IRQ_MASK) is set to 0. The pin remains at
high level until the end of the frame receive procedure.
For further details refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
Refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
• Bit 1 - IRQ_MASK_MODE
The AT86RF231 supports polling of interrupt events. Interrupt polling can be enabled by register
bit IRQ_MASK_MODE. Even if an interrupt request is masked by the corresponding bit in register 0x0E (IRQ_MASK), the event is indicated in register 0x0F (IRQ_STATUS).
Table 6-10.
Interrupt Polling Configuration
Register Bit
IRQ_MASK_MODE
Value
Description
0
Interrupt polling disabled
1
Interrupt polling enabled
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• Bit 0 - IRQ_POLARITY
The default polarity of the IRQ pin is active high. The polarity can be configured to active low via
register bit IRQ_POLARITY, see Table 6-11 on page 32.
Table 6-11.
Configuration of Pin 24 (IRQ)
Register Bit
IRQ_POLARITY
Value
Description
0
pin IRQ high active
1
pin IRQ low active
This setting does not affect the polarity of the Frame Buffer Empty Indicator, refer to Section
11.7 “Frame Buffer Empty Indicator” on page 152. The Frame Buffer Empty Indicator is always
active high.
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7. Operating Modes
7.1
Basic Operating Mode
This section summarizes all states to provide the basic functionality of the AT86RF231, such as
receiving and transmitting frames, the power up sequence and sleep. The Basic Operating
Mode is designed for IEEE 802.15.4 and ISM applications; the corresponding radio transceiver
states are shown in Figure 7.1 on page 33.
Basic Operating Mode State Diagram (for timing refer to Table 7-1 on page 42)
P_ON
SLEEP
(Power-on after VDD)
(Sleep State)
XOSC=ON
Pull=ON
XOSC=OFF
Pull=OFF
_O
N
_O
FF
RX
TR
X
H
=
4
11
RX_ON
PLL_ON
(PLL State)
PLL_ON 9
10
BUSY_TX
(Transmit State)
=
14
L
=
TR
SL
P_
SL
P_
TR
FORCE_PLL_ON
(all states except SLEEP,
P_ON, TRX_OFF, RX_ON_NOCLK)
Legend:
Blue: SPI Write to Register TRX_STATE (0x02)
Red: Control signals via IC Pin
Green: Event
Basic Operating Mode States
CLKM=OFF
X
7.1.1
Frame
End
SLP_TR = H
or
TX_START
H
SHR
Detected
N
RX_ON
(Rx Listen State)
Frame
End
RX_ON_NOCLK
(Rx Listen State)
8
RESET
O
L_
PL
BUSY_RX
(Receive State)
FF
_O
SHR
Detected
5
X
TR
6
/RST = H
(all states except P_ON)
XOSC=ON
Pull=OFF
7
/RST = L
13
(Clock State)
(all states except SLEEP)
(from all states)
R
TRX_OFF
12
3
SL
P_
T
F
OF
X_
TR
FORCE_TRX_OFF
2
1
SL
P_
TR
=
L
Figure 7-1.
State transition number, see Table 7-1
State Control
The radio transceiver states are controlled either by writing commands to register bits
TRX_CMD (register 0x02, TRX_STATE), or directly by two signal pins: pin 11 (SLP_TR) and
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pin 8 (/RST). A successful state change can be verified by reading the radio transceiver status
from register 0x01 (TRX_STATUS).
If TRX_STATUS = 0x1F (STATE_TRANSITION_IN_PROGRESS) the AT86RF231 is on a state
transition. Do not try to initiate a further state change while the radio transceiver is in
STATE_TRANSITION_IN_PROGRESS.
Pin SLP_TR is a multifunctional pin, refer to Section 6.5 “Sleep/Wake-up and Transmit Signal
(SLP_TR)” on page 27. Dependent on the radio transceiver state, a rising edge of pin SLP_TR
causes the following state transitions:
• TRX_OFF
⇒
SLEEP
(level sensitive)
• RX_ON
⇒
RX_ON_NOCLK
(level sensitive)
• PLL_ON
⇒
BUSY_TX
Whereas the falling edge of pin SLP_TR causes the following state transitions:
• SLEEP
⇒
TRX_OFF
(level sensitive)
• RX_ON_NOCLK
⇒
RX_ON
(level sensitive)
Pin 8 (/RST) causes a reset of all registers (register bits CLKM_CTRL are shadowed, for details
refer to Section 9.6.4 “Master Clock Signal Output (CLKM)” on page 117) and forces the radio
transceiver into TRX_OFF state. However, if the device was in P_ON state it remains in the
P_ON state.
For all states except SLEEP, the state change commands FORCE_TRX_OFF or TRX_OFF lead
to a transition into TRX_OFF state. If the radio transceiver is in active receive or transmit states
(BUSY_*), the command FORCE_TRX_OFF interrupts these active processes, and forces an
immediate transition to TRX_OFF. In contrast a TRX_OFF command is stored until an active
state (receiving or transmitting) has been finished. After that the transition to TRX_OFF is
performed.
For a fast transition from receive or active transmit states to PLL_ON state the command
FORCE_PLL_ON is provided. In contrast to FORCE_TRX_OFF this command does not disable
the PLL and the analog voltage regulator AVREG. It is not available in states SLEEP, P_ON,
RESET, TRX_OFF, and all *_NOCLK states.
The completion of each requested state change shall always be confirmed by reading the register bits TRX_STATUS (register 0x01, TRX_STATUS).
7.1.2
7.1.2.1
Basic Operating Mode Description
P_ON - Power-On after VDD
When the external supply voltage (VDD) is firstly applied to the AT86RF231, the radio transceiver
goes into the P_ON state performing an on-chip reset. The crystal oscillator is activated and the
default 1 MHz master clock is provided at pin 17 (CLKM) after the crystal oscillator has stabilized. CLKM can be used as a clock source to the microcontroller. The SPI interface and digital
voltage regulator are enabled.
The on-chip power-on-reset sets all registers to their default values. A dedicated reset signal
from the microcontroller at pin 8 (/RST) is not necessary, but recommended for hardware / software synchronization reasons.
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All digital inputs are pulled-up or pulled-down during P_ON state, refer to Section 1.3.2 “Pull-Up
and Pull-Down Configuration” on page 7. This is necessary to support microcontrollers where
GPIO signals are floating after power on or reset. The input pull-up and pull-down circuitry is disabled when the radio transceiver leaves the P_ON state. Output pins DIG1/DIG2 are pulleddown to digital ground, whereas pins DIG3/DIG4 are pulled-down to analog ground, unless their
configuration is changed.
Prior to leaving P_ON, the microcontroller must set the pins to the default operating values:
SLP_TR = L, /RST = H and /SEL = H.
All interrupts are disabled by default. Thus, interrupts for state transition control are to be
enabled first, e.g. enable IRQ_4 (AWAKE_END) to indicate a state transition to TRX_OFF state
or interrupt IRQ_0 (PLL_LOCK) to signal a locked PLL in PLL_ON state. In P_ON state a first
access to the radio transceiver registers is possible after a default 1 MHz master clock is provided at pin 17 (CLKM), refer to Table 7-1 on page 42.
Once the supply voltage has stabilized and the crystal oscillator has settled (see Section 12.5
“General RF Specifications” on page 158, parameter 12.5.7), a valid SPI write access to register
bits TRX_CMD (register 0x02, TRX_STATE) with the command TRX_OFF or
FORCE_TRX_OFF initiate a state change from P_ON towards TRX_OFF state, which is then
indicated by an AWAKE_END interrupt if enabled.
7.1.2.2
SLEEP - Sleep State
In SLEEP state, the entire radio transceiver is disabled. No circuitry is operating. The radio
transceiver current consumption is reduced to leakage current only. This state can only be
entered from state TRX_OFF, by setting the pin SLP_TR = H.
If CLKM is enabled, the SLEEP state is entered 35 CLKM cycles after the rising edge at pin 11
(SLP_TR). At that time CLKM is turned off. If the CLKM output is already turned off (bits
CLKM_CTRL = 0 in register 0x03), the SLEEP state is entered immediately. At clock rates
250 kHz and 62.5 kHz, the main clock at pin 17 (CLKM) is turned off immediately.
Setting SLP_TR = L returns the radio transceiver to the TRX_OFF state. During SLEEP the register contents remains valid while the content of the Frame Buffer and the security engine (AES)
are cleared.
/RST = L in SLEEP state returns the radio transceiver to TRX_OFF state and thereby sets all
registers to their default values. Exceptions are register bits CLKM_CTRL (register 0x03,
TRX_CTRL_0). These register bits require a specific treatment, for details see Section 9.6.4
“Master Clock Signal Output (CLKM)” on page 117.
7.1.2.3
TRX_OFF - Clock State
In TRX_OFF the crystal oscillator is running and the master clock is available at pin 17 (CLKM)
after the crystal oscillator has stabilized. The SPI interface and digital voltage regulator are
enabled, thus the radio transceiver registers, the Frame Buffer and security engine (AES) are
accessible (see Section 9.3 “Frame Buffer” on page 107 and Section 11.1 “Security Module
(AES)” on page 128).
In contrast to P_ON state the pull-up and pull-down configuration is disabled.
Pin 11 (SLP_TR) and pin 8 (/RST) are available for state control. Note that the analog front-end
is disabled during TRX_OFF.
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Entering the TRX_OFF state from P_ON, SLEEP, or RESET state is indicated by interrupt
IRQ_4 (AWAKE_END).
7.1.2.4
PLL_ON - PLL State
Entering the PLL_ON state from TRX_OFF state enables the analog voltage regulator (AVREG)
first. After the voltage regulator has been settled, the PLL frequency synthesizer is enabled.
When the PLL has been settled at the receive frequency to a channel defined by register bits
CHANNEL (register 0x08, PHY_CC_CCA), a successful PLL lock is indicated by issuing an
interrupt IRQ_0 (PLL_LOCK).
If an RX_ON command is issued in PLL_ON state, the receiver is immediately enabled. If the
PLL has not been settled before the state change nevertheless takes place. Even if the register
bits TRX_STATUS (register 0x01, TRX_STATUS) indicates RX_ON, actual frame reception can
only start once the PLL has locked.
The PLL_ON state corresponds to the TX_ON state in IEEE 802.15.4.
7.1.2.5
RX_ON and BUSY_RX - RX Listen and Receive State
In RX_ON state the receiver blocks and the PLL frequency synthesizer are enabled.
The AT86RF231 receive mode is internally separated into RX_ON state and BUSY_RX state.
There is no difference between these states with respect to the analog radio transceiver circuitry, which are always turned on. In both states the receiver and the PLL frequency
synthesizer are enabled.
During RX_ON state the receiver listens for incoming frames. After detecting a valid synchronization header (SHR), the AT86RF231 automatically enters the BUSY_RX state. The reception
of a valid PHY header (PHR) generates an IRQ_2 (RX_START) and receives and demodulates
the PSDU data.
During PSDU reception the frame data are stored continuously in the Frame Buffer until the last
byte was received. The completion of the frame reception is indicated by an interrupt IRQ_3
(TRX_END) and the radio transceiver reenters the state RX_ON. At the same time the register
bit RX_CRC_VALID (register 0x06, PHY_RSSI) is updated with the result of the FCS check (see
Section 8.2 “Frame Check Sequence (FCS)” on page 85).
Received frames are passed to the frame filtering unit, refer to Section 7.2.3.5 “Frame Filtering”
on page 61. If the content of the MAC addressing fields (refer to IEEE 802.15.4-2006,
Section 7.2.1) of a frame matches to the expected addresses, which is further dependent on the
addressing mode, an address match interrupt IRQ_5 (AMI) is issued, refer to Section 6.6 “Interrupt Logic” on page 29. The expected address values are to be stored in registers 0x20 - 0x2B
(Short address, PAN-ID and IEEE address). Frame filtering is available in Basic and Extended
Operating Mode, refer to Section 7.2.3.5 “Frame Filtering” on page 61.
Leaving state RX_ON is only possible by writing a state change command to register bits
TRX_CMD in register 0x02 (TRX_STATE).
7.1.2.6
RX_ON_NOCLK - RX Listen State without CLKM
If the radio transceiver is listening for an incoming frame and the microcontroller is not running
an application, the microcontroller may be powered down to decrease the total system power
consumption. This specific power-down scenario for systems running in clock synchronous
mode (see Section 6. “Microcontroller Interface” on page 16), is supported by the AT86RF231
using the state RX_ON_NOCLK.
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This state can only be entered by setting pin 11 (SLP_TR) = H while the radio transceiver is in
the RX_ON state, refer to Section 7.1.2.5 “RX_ON and BUSY_RX - RX Listen and Receive
State” on page 36. Pin 17 (CLKM) is disabled 35 clock cycles after the rising edge at the
SLP_TR pin, see Figure 6-16 on page 28. This allows the microcontroller to complete its powerdown sequence.
Note that for CLKM clock rates 250 kHz and 62.5 kHz the master clock signal CLKM is switched
off immediately after rising edge of SLP_TR.
The reception of a frame shall be indicated to the microcontroller by an interrupt indicating the
receive status. CLKM is turned on again, and the radio transceiver enters the BUSY_RX state
(see Section 6.5 “Sleep/Wake-up and Transmit Signal (SLP_TR)” on page 27 and Figure 6-16
on page 28). Using this radio transceiver state it is essential to enable at least one interrupt indicating the reception status. Otherwise the reception of a frame does not activate CLKM and the
microcontroller remains in its power-down mode.
After the receive transaction has been completed, the radio transceiver enters the RX_ON state.
The radio transceiver only reenters the RX_ON_NOCLK state, when the next rising edge of pin
SLP_TR pin occurs.
If the AT86RF231 is in the RX_ON_NOCLK state, and pin SLP_TR is reset to logic low, it enters
the RX_ON state, and it starts to supply clock on the CLKM pin again.
In states RX_ON_NOCLK and RX_ON, the radio transceiver current consumptions are equivalent. However, the RX_ON_NOCLK current consumption is reduced by the current required for
driving pin 17 (CLKM).
Note
• A reset in state RX_ON_NOCLK requires further to reset pin SLP_TR to logic low, otherwise
the radio transceiver enters directly the SLEEP state.
7.1.2.7
BUSY_TX - Transmit State
A transmission can only be initiated in state PLL_ON. There are two ways to start a
transmission:
• Rising edge of pin 11 (SLP_TR)
• TX_START command to register bits TRX_CMD (register 0x02, TRX_STATE).
Either of these causes the radio transceiver into the BUSY_TX state.
During the transition to BUSY_TX state, the PLL frequency shifts to the transmit frequency. The
actual transmission of the first data chip of the SHR starts after 16 µs to allow PLL settling and
PA ramp-up, see Figure 7-6 on page 41. After transmission of the SHR, the Frame Buffer content is transmitted. In case the PHR indicates a frame length of zero, the transmission is aborted.
After the frame transmission has completed, the AT86RF231 automatically turns off the power
amplifier, generates an IRQ_3 (TRX_END) interrupt and returns into PLL_ON state.
7.1.2.8
RESET State
The RESET state is used to set back the state machine and to reset all registers of the
AT86RF231 to their default values, exception are register bits CLKM_CTRL (register 0x03,
TRX_CTRL_0). These register bits require a specific treatment, for details see Section 9.6.4
“Master Clock Signal Output (CLKM)” on page 117.
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A reset forces the radio transceiver into TRX_OFF state. If the device is still in the P_ON state it
remains in the P_ON state though.
A reset is initiated with pin /RST = L and the state is left after setting /RST = H. The reset pulse
should have a minimum length as specified in Section 12.4 “Digital Interface Timing Characteristics” on page 157 see parameter 12.4.13.
During reset the microcontroller has to set the radio transceiver control pins SLP_TR and /SEL
to their default values.
An overview about the register reset values is provided in Table 14-1 on page 170.
7.1.3
Interrupt Handling
All interrupts provided by the AT86RF231 (see Table 6-9 on page 29) are supported in Basic
Operating Mode.
For example, interrupts are provided to observe the status of radio transceiver RX and
TX operations.
On receive IRQ_2 (RX_START) indicates the detection of a valid PHR first, IRQ_5 (AMI) an
address match and IRQ_3 (TRX_END) the completion of the frame reception.
On transmit IRQ_3 (TRX_END) indicates the completion of the frame transmission.
Figure 7-2 on page 39 shows an example for a transmit/receive transaction between two
devices and the related interrupt events in Basic Operating Mode. Device 1 transmits a frame
containing a MAC header (in this example of length 7), payload and valid FCS. The frame is
received by Device 2 which generates the interrupts during the processing of the incoming
frame. The received frame is stored in the Frame Buffer.
The first interrupt IRQ_2 (RX_START) signals the reception of a valid PHR.
If the received frame passes the address filter, refer to Section 7.2.3.5 “Frame Filtering” on page
61, an address match interrupt IRQ_5 (AMI) is issued after the reception of the MAC
header (MHR).
In Basic Operating Mode the third interrupt IRQ_3 (TRX_END) is issued at the end of the
received frame. In Extended Operating Mode, refer to Section 7.2 “Extended Operating Mode”
on page 47; the interrupt is only issued if the received frame passes the address filter and the
FCS is valid. Further exceptions are explained in Section 7.2 “Extended Operating Mode” on
page 47.
Processing delay tIRQ is a typical value, refer to Section 12.4 “Digital Interface Timing Characteristics” on page 157.
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Timing of RX_START, AMI and TRX_END Interrupts in Basic Operating Mode
TRX_STATE
128
160
PLL_ON
192
192+(9+m)*32
BUSY_TX
Time [µs]
PLL_ON
TX
(Device1)
-16 0
SLP_TR
IRQ
IRQ_3 (TRX_END)
16 µs
Number of Octets
Frame Content
TRX_STATE
4
1
1
7
m
2
Preamble
SFD
PHR
MHR
MSDU
FCS
RX_ON
BUSY_RX
IRQ
IRQ_2 (RX_START)
Interrupt latency
7.1.4
7.1.4.1
Frame
on Air
Typ. Processing Delay
RX_ON
IRQ_5 (AMI)
TRX_END
tIRQ
tIRQ
tIRQ
RX
(Device 2)
Figure 7-2.
Basic Operating Mode Timing
The following paragraphs depict state transitions and their timing properties. Timing figures are
explained in Table 7-1 on page 42 and Section 12.4 “Digital Interface Timing Characteristics” on
page 157.
Power-on Procedure
The power-on procedure to P_ON state is shown in Figure 7-3 on page 39.
Figure 7-3.
Power-on Procedure to P_ON State
0
100
Event
VDD on
State
P_ON
Block
XOSC, DVREG
Time
400
Time [µs]
CLKM on
tTR1
When the external supply voltage (VDD) is firstly supplied to the AT86RF231, the radio transceiver enables the crystal oscillator (XOSC) and the internal 1.8 V voltage regulator for the
digital domain (DVREG). After tTR1 = 330 µs (typ.), the master clock signal is available at pin 17
(CLKM) at default rate of 1 MHz. If CLKM is available the SPI is already enabled and can be
used to control the transceiver. As long as no state change towards state TRX_OFF is performed the radio transceiver remains in P_ON state.
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7.1.4.2
Wake-up Procedure
The wake-up procedure from SLEEP state is shown in Figure 7-4 on page 40.
Figure 7-4.
Wake-up Procedure from SLEEP State
0
400
200
CLKM on
SLP_TR = L
Event
State
100
IRQ_4 (AWAKE_END)
TRX_OFF
SLEEP
Block
Time [µs]
XOSC, DVREG
FTN XOSC, DVREG
Time
tTR2
The radio transceivers SLEEP state is left by releasing pin SLP_TR to logic low. This restarts the
XOSC and DVREG. After tTR2 = 380 µs (typ.) the radio transceiver enters TRX_OFF state. The
internal clock signal is available and provided to pin 17 (CLKM), if CLKM was enabled.
This procedure is similar to the Power-On Procedure. However the radio transceiver continues
the state change automatically to the TRX_OFF state. During this the filter-tuning network (FTN)
calibration is performed. Entering TRX_OFF state is signaled by IRQ_4 (AWAKE_END), if this
interrupt was enabled by the appropriate mask register bit.
7.1.4.3
PLL_ON and RX_ON States
The transition from TRX_OFF to PLL_ON and RX_ON mode is shown in Figure 7-5 on page 40.
Figure 7-5.
Transmission from TRX_OFF to PLL_ON and RX_ON State
0
100
IRQ_0 (PLL_LOCK)
Event
State
Note:
PLL_ON
TRX_OFF
Block
AVREG
Command
PLL_ON
Time
Time [µs]
PLL
RX_ON
RX
R_ON
tTR4
tTR8
If TRX_CMD = RX_ON in TRX_OFF state RX_ON state is entered immediately, even if the PLL
has not settled.
In TRX_OFF state, entering the commands PLL_ON or RX_ON initiates a ramp-up sequence of
the internal 1.8V voltage regulator for the analog domain (AVREG). RX_ON state can be
entered any time from PLL_ON state regardless whether the PLL has already locked, which is
indicated by IRQ_0 (PLL_LOCK).
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7.1.4.4
BUSY_TX and RX_ON States
The transition from PLL_ON to BUSY_TX state and subsequent to RX_ON state is shown in
Figure 7-6 on page 41.
Figure 7-6.
PLL_ON to BUSY_TX to RX_ON Timing
0
Pin
16
x
x + 32 Time [µs]
SLP_TR
PLL_ON
State
Block
BUSY_TX
PLL
Command
PA
RX_ON
PA, TX
or command TX_START
Time
PLL
RX
RX_ON
tTR10
tTR11
Starting from PLL_ON state it is further assumed that the PLL is already locked. A transmission
is initiated either by a rising edge of pin 11 (SLP_TR) or by command TX_START. The PLL settles to the transmit frequency and the PA is enabled.
tTR10 = 16 µs after initiating the transmission the AT86RF231 changes into BUSY_TX state and
the internally generated SHR is transmitted. After that the PSDU data are transmitted from the
Frame Buffer.
After completing the frame transmission, indicated by IRQ_3 (TRX_END), the PLL settles back
to the receive frequency within tTR11 = 32 µs in state PLL_ON.
If during TX_BUSY the radio transmitter is programmed to change to a receive state it automatically proceeds the state change to RX_ON state after finishing the transmission.
7.1.4.5
Reset Procedure
The radio transceiver reset procedure is shown in Figure 7-7 on page 41.
Figure 7-7.
Reset Procedure
x
0
x + 10
x + 40
Event
State
Block
Time [µs]
[IRQ_4 (AWAKE_END)]
various
TRX_OFF
XOSC, DVREG
FTN
XOSC, DVREG
Pin /RST
Time
Note:
>t10
>t11
tTR13
Timing figure tTR13 refers to Table 7-1 on page 42, t10, t11 refers to Section 12.4 “Digital Interface
Timing Characteristics” on page 157.
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/RST = L sets all registers to their default values. Exceptions are register bits CLKM_CTRL (register 0x03, TRX_CTRL_0), refer to Section 9.6.4 “Master Clock Signal Output (CLKM)” on page
117.
After releasing the reset pin (/RST = H) the wake-up sequence including an FTN calibration
cycle is performed, refer to Section 9.8 “Automatic Filter Tuning (FTN)” on page 125. After that
the TRX_OFF state is entered.
Figure 7-7 on page 41 illustrates the reset procedure once the P_ON state was left and the radio
transceiver was not in SLEEP state.
The reset procedure is identical for all originating radio transceiver states except of state P_ON
and SLEEP state. Instead, here the procedure described in Section 7.1.2.1 “P_ON - Power-On
after VDD” on page 34 must be followed to enter the TRX_OFF state.
If the radio transceiver was in SLEEP state, the XOSC and DVREG are enabled before entering
TRX_OFF state.
If register TRX_STATUS indicates STATE_TRANSITION_IN_PROGRESS during system initialization until the AT86RF231 reaches TRX_OFF, do not try to initiate a further state change while
the radio transceiver is in this state.
Notes
• The reset impulse should have a minimum length t10 = 625 ns as specified in Section 12.4
“Digital Interface Timing Characteristics” on page 157, see parameter 12.4.13.
• An access to the device should not occur earlier than t11 625 ns after releasing the pin
/RST; refer to Section 12.4 “Digital Interface Timing Characteristics” on page 157, parameter
12.4.14.
• A reset overrides an SPI command request that might be queued.
7.1.4.6
State Transition Timing Summary
The transition numbers correspond to Figure 7-1 on page 33 and do not include SPI access time
if not otherwise stated. See measurement setup in Figure 5-1 on page 12.
Table 7-1.
State Transition Timing
No
Symbol
Transition
Time [µs], (type)
1
tTR1
P_ON
⇒
until CLKM
available
330
Depends on external capacitor at DVDD (1 µF nom) and crystal
oscillator setup (CL = 10 pF)
2
tTR2
SLEEP
⇒
TRX_OFF
380
Depends on external capacitor at DVDD (1 µF nom) and crystal
oscillator setup (CL = 10 pF)
TRX_OFF state indicated by IRQ_4 (AWAKE_END)
3
tTR3
TRX_OFF
⇒
SLEEP
4
tTR4
TRX_OFF
⇒
PLL_ON
5
tTR5
PLL_ON
⇒
TRX_OFF
6
tTR6
TRX_OFF
⇒
RX_ON
7
tTR7
RX_ON
⇒
TRX_OFF
1
8
tTR8
PLL_ON
⇒
RX_ON
1
9
tTR9
RX_ON
⇒
PLL_ON
1
35*1/fCLKM
110
Comments
For fCLKM > 250 kHz
Depends on external capacitor at AVDD (1 µF nom)
1
110
Depends on external capacitor at AVDD (1 µF nom)
Transition time is also valid for TX_ARET_ON, RX_AACK_ON
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Table 7-1.
No
Symbol
10
tTR10
11
State Transition Timing (Continued)
Transition
Time [µs], (type)
Comments
PLL_ON
⇒
BUSY_TX
16
When asserting pin 11 (SLP_TR) or TRX_CMD = TX_START
first symbol transmission is delayed by 16 µs delay (PLL
settling and PA ramp up)
tTR11
BUSY_TX
⇒
PLL_ON
32
PLL settling time from TX_BUSY to PLL_ON state
12
tTR12
All states
⇒
TRX_OFF
1
Using TRX_CMD = FORCE_TRX_OFF (see register 0x02,
TRX_STATE),
Not valid for SLEEP state
13
tTR13
RESET
⇒
TRX_OFF
37
Valid for P_ON or SLEEP state
14
tTR14
Various
states
⇒
PLL_ON
1
Using TRX_CMD = FORCE_PLL_ON (see register 0x02,
TRX_STATE),
Not valid for SLEEP, P_ON, RESET, TRX_OFF and *_NOCLK
The state transition timing is calculated based on the timing of the individual blocks shown in
Figure 7-3 on page 39 to Figure 7-7 on page 41. The worst case values include maximum operating temperature, minimum supply voltage, and device parameter variations.
Table 7-2.
Analog Block Initialization and Settling Time
No
Symbol
Block
Time [µs], (type)
Time [µs], (max)
15
tTR15
XOSC
330
1000
16
tTR16
FTN
17
tTR17
DVREG
60
1000
Depends on external bypass capacitor at DVDD
(CB3 = 1 µF nom., 10 µF worst case), depends on VDD
18
tTR18
AVREG
60
1000
Depends on external bypass capacitor at AVDD
(CB1 = 1 µF nom, 10 µF worst case), depends on VDD
19
tTR19
PLL, initial
110
155
PLL settling time TRX_OFF ⇒PLL_ON, including 60 µs
AVREG settling time
20
tTR20
PLL settling
11
24
Settling time between channels switch
21
tTR21
PLL, CF cal
35
22
tTR22
PLL, DCU cal
6
PLL DCU calibration, refer to Section 9.7.4
23
tTR23
PLL, RX ⇒TX
16
Maximum PLL settling time RX ⇒TX
24
tTR24
PLL, TX ⇒RX
32
Maximum PLL settling time TX ⇒RX
25
tTR25
RSSI, update
2
RSSI update period in receive states, refer to Section 8.3.2
26
tTR26
ED
27
tTR27
SHR, sync
28
tTR28
CCA
29
tTR29
Random value
25
Comment
Leaving SLEEP state, depends on crystal Q factor and
load capacitor
FTN tuning time fixed
PLL center frequency calibration, refer to Section 9.7.4
140
96
ED measurement period, refer to Section 8.4.2
Typical SHR synchronisation period, refer to Section 8.4.2
140
1
CCA measurement period, refer to Section 8.5.2
Random value update period, refer to Section 11.2.1
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7.1.5
Register Description
Register 0x01 (TRX_STATUS):
A read access to TRX_STATUS register signals the current radio transceiver state. A state
change is initiated by writing a state transition command to register bits TRX_CMD (register
0x02, TRX_STATE). Alternatively a state transition can be initiated by the rising edge of pin 11
(SLP_TR) in the appropriate state.
This register is used for Basic and Extended Operating Mode, refer to Section 7.2 “Extended
Operating Mode” on page 47.
Bit
7
6
5
CCA_DONE
CCA_STATUS
Reserved
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
+0x01
4
3
2
1
0
TRX_STATUS
TRX_STATUS
• Bit 7 - CCA_DONE
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94.
• Bit 6 - CCA_STATUS
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94.
• Bit 5 - Reserved
• Bit [4:0] - TRX_STATUS
The register bits TRX_STATUS signals the current radio transceiver status. If the requested
state transition is not completed yet, the TRX_STATUS returns
STATE_TRANSITION_IN_PROGRESS. Do not try to initiate a further state change while the
radio transceiver is in STATE_TRANSITION_IN_PROGRESS. State transition timings are
defined in Table 7-1 on page 42.
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Table 7-3.
Radio Transceiver Status, Register Bits TRX_STATUS
Register Bits
Value
State Description
TRX_STATUS
0x00
P_ON
0x01
BUSY_RX
0x02
BUSY_TX
0x06
RX_ON
0x08
TRX_OFF (CLK Mode)
0x09
PLL_ON (TX_ON)
(3)
SLEEP
(1)
BUSY_RX_AACK
(1)
0x12
BUSY_TX_ARET
0x16(1)
RX_AACK_ON
(1)
TX_ARET_ON
0x0F
0x11
0x19
0x1C
(1)
RX_ON_NOCLK
0x1D
RX_AACK_ON_NOCLK
0x1E(1)
BUSY_RX_AACK_NOCLK
0x1F(2)
STATE_TRANSITION_IN_PROGRESS
All other values are reserved
Notes:
1. Extended Operating Mode only, refers to Section 7.2 “Extended Operating Mode” on page 47.
2. Do not try to initiate a further state change while the radio transceiver is in
STATE_TRANSITION_IN_PROGRESS state.
3. In SLEEP state register not accessible.
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Register 0x02 (TRX_STATE):
The radio transceiver states are controlled via register bits TRX_CMD, which receives the state
transition commands.
This register is used for Basic and Extended Operating Mode, refer to Section 7.2 “Extended
Operating Mode” on page 47.
Bit
7
+0x02
6
5
4
3
TRAC_STATUS
2
1
0
TRX_CMD
TRX_STATE
Read/Write
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
• Bit [7:5] - TRAC_STATUS
Refer to Section 7.2.7 “Register Description - Control Registers” on page 68.
• Bit [4:0] - TRX_CMD
A write access to register bits TRX_CMD initiate a radio transceiver state transition towards the
new state as defined by the write access:
Table 7-4.
State Control Command, Register Bits TRX_CMD
Register Bit
Value
State Description
TRX_CMD
0x00
NOP
0x02
TX_START
0x03
FORCE_TRX_OFF
0x04(1)
FORCE_PLL_ON
0x06
RX_ON
0x08
TRX_OFF (CLK Mode)
0x09
PLL_ON (TX_ON)
(2)
RX_AACK_ON
(2)
TX_ARET_ON
0x16
0x19
All other values are reserved and mapped to NOP
Notes:
1. FORCE_PLL_ON is not valid for states SLEEP, P_ON, RESET, TRX_OFF, and all *_NOCLK
states, as well as STATE_TRANSITION_IN_PROGRESS towards these states.
2. Extended Operating Mode only, refers to Section 7.2.7 “Register Description - Control Registers” on page 68.
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7.2
Extended Operating Mode
The Extended Operating Mode is a hardware MAC accelerator and goes beyond the basic radio
transceiver functionality provided by the Basic Operating Mode. It handles time critical MAC
tasks, requested by the IEEE 802.15.4 standard, by hardware, such as automatic acknowledgement, automatic CSMA-CA and retransmission. This results in a more efficient IEEE 802.15.4
software MAC implementation including reduced code size and may allow the use of a smaller
microcontroller or to operate at low clock rates.
The Extended Operating Mode is designed to support IEEE 802.15.4-2006 compliant frames;
the mode is backward compatible to IEEE 802.15.4-2003 and supports non IEEE 802.15.4 compliant frames. This mode comprises the following procedures:
Automatic acknowledgement (RX_AACK) divides into the tasks:
• Frame reception and automatic FCS check
• Configurable addressing fields check
• Interrupt indicating address match
• Interrupt indicating frame reception, if it passes address filtering and FCS check
• Automatic ACK frame transmission (if the received frame passed the address filter and FCS
check and if an ACK is required by the frame type and ACK request)
• Support of slotted acknowledgment using SLP_TR pin
Automatic CSMA-CA and Retransmission (TX_ARET) divides into the tasks:
• CSMA-CA including automatic CCA retry and random back-off
• Frame transmission and automatic FCS field generation
• Reception of ACK frame (if an ACK was requested)
• Automatic frame retry if ACK was expected but not received
• Interrupt signaling with transaction status
Automatic FCS check and generation, refer to Section 8.2 “Frame Check Sequence (FCS)” on
page 85, is used by the RX_AACK and TX_ARET modes. In RX_AACK mode, an automatic
FCS check is always performed for incoming frames.
In TX_ARET mode, an ACK, received within the time required by IEEE 802.15.4, is accepted if
the FCS is valid, and if the sequence number of the ACK matches the sequence number of the
previously transmitted frame. Dependent on the value of the frame pending subfield in the
received acknowledgement frame the transaction status is set, see Table 7-16 on page 70.
An AT86RF231 state diagram including the Extended Operating Mode states is shown in Figure
7-8 on page 48. Yellow marked states represent the Basic Operating Mode; blue marked states
represent the Extended Operating Mode.
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Extended Operating Mode State Diagram
P_ON
SLEEP
(Power-on after VDD)
(Sleep State)
XOSC=ON
Pull=ON
XOSC=OFF
Pull=OFF
2
H
TRX_OFF
12
13
(Clock State)
(all modes except SLEEP)
(from all states)
/RST = L
SL
P
FF
_O
FORCE_TRX_OFF
1
3
_T
R=
X
TR
SL
P_
TR
=
L
Figure 7-8.
/RST = H
RESET
(all modes except P_ON)
X_
OF
F
_O
RX
Frame
End
PLL_ON
PLL_ON
9
=H
PLL_ON
TX_ARET_ON
TX
_A
RE
T_
TR
ON
X_
OF
F
RX
_
From / To
TRX_OFF
SLP_TR=H
or
TX_START
CLKM=OFF
SHR
Detected
Frame
Rejected
SLP_TR=H
Frame
Accepted
BUSY_RX_
AACK_NOCLK
RX_AACK_ON
SLP_TR=L
Transaction
Finished
Frame
End
see notes
SHR
Detected
BUSY_RX_AACK
BUSY_TX
(Transmit State)
FORCE_PLL_ON
N
N
AA
CK
_O
TR
N
X_
OF
F
(Rx Listen State)
AC
K_
O
L_
O
From / To
TRX_OFF
PL
RX_ON_NOCLK
CLKM=OFF
11
(PLL State)
14
RX
_A
R
RX_ON
SLP_TR=H
or
TX_START
10
=L
T
P_
L
S
TR
(Rx Listen State)
SL
P_
TR
SHR
Detected
(Receive State)
8
RX_ON
4
F
OF
BUSY_RX
SHR
Detected
X_
TR
6
5
ON
L_
7
PL
N
XOSC=ON
Pull=OFF
RX_AACK_
ON_NOCLK
CLKM=OFF
TX_ARET_ON
Frame
End
BUSY_TX_ARET
Legend:
Blue: SPI Write to Register TRX_STATE (0x02)
Red: Control signals via IC Pin
Green: Event
Basic Operating Mode States
Extended Operating Mode States
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7.2.1
State Control
The Extended Operating Mode states RX_AACK and TX_ARET are controlled via register bits
TRX_CMD (register 0x02, TRX_STATE), which receives the state transition commands. The
states are entered from TRX_OFF or PLL_ON state as illustrated by Figure 7-8 on page 48. The
completion of each state change command shall always be confirmed by reading the register
0x01 (TRX_STATUS).
RX_AACK - Receive with Automatic ACK
A state transition to RX_AACK_ON from PLL_ON or TRX_OFF is initiated by writing the command RX_AACK_ON to the register bits TRX_CMD. The state change can be confirmed by
reading register 0x01 (TRX_STATUS), those changes to RX_AACK_ON or BUSY_RX_AACK
on success. The latter one is returned if a frame is currently about being received.
The RX_AACK state is left by writing command TRX_OFF or PLL_ON to the register bits
TRX_CMD. If the AT86RF231 is within a frame receive or acknowledgment procedure
(BUSY_RX_AACK) the state change is executed after finish. Alternatively, the commands
FORCE_TRX_OFF or FORCE_PLL_ON can be used to cancel the RX_AACK transaction and
change into radio transceiver state TRX_OFF or PLL_ON, respectively.
TX_ARET - Transmit with Automatic Retry and CSMA-CA Retry
Similarly, a state transition to TX_ARET_ON from PLL_ON or TRX_OFF is initiated by writing
command TX_ARET_ON to register bits TRX_CMD. The radio transceiver is in the
TX_ARET_ON state after TRX_STATUS (register 0x01) changes to TX_ARET_ON. The
TX_ARET transaction is started with a rising edge of pin 11 (SLP_TR) or writing the command
TX_START to register bits TRX_CMD.
The TX_ARET state is left by writing the command TRX_OFF or PLL_ON to the register bits
TRX_CMD. If the AT86RF231 is within a CSMA-CA, a frame-transmit or an acknowledgment
procedure (BUSY_TX_ARET) the state change is executed after finish. Alternatively the command FORCE_TRX_OFF or FORCE_PLL_ON can be used to instantly terminate the TX_ARET
transaction and change into radio transceiver state TRX_OFF or PLL_ON, respectively.
Note
• A state change request from TRX_OFF to RX_AACK_ON or TX_ARET_ON internally passes the state
PLL_ON to initiate the radio transceiver. Thus the readiness to receive or transmit data is delayed
accordingly. It is recommended to use interrupt IRQ_0 (PLL_LOCK) as an indicator.
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7.2.2
Configuration
The use of the Extended Operating Mode is based on Basic Operating Mode functionality. Only
features beyond the basic radio transceiver functionality are described in the following sections.
For details on the Basic Operating Mode refer to Section 7.1 “Basic Operating Mode” on page
33.
When using the RX_AACK or TX_ARET modes, the following registers needs to be configured.
RX_AACK configuration steps:
• Short address, PAN-ID and IEEE address
registers 0x20 - 0x2B
• Configure RX_AACK properties
registers 0x2C, 0x2E
– Handling of Frame Version Subfield
– Handling of Pending Data Indicator
– Characterize as PAN coordinator
– Handling of Slotted Acknowledgement
• Additional Frame Filtering Properties
registers 0x17, 0x2E
– Promiscuous Mode
– Enable or disable automatic ACK generation
– Handling of reserved frame types
The addresses for the address match algorithm are to be stored in the appropriate address registers. Additional control of the RX_AACK mode is done with register 0x17 (XAH_CTRL_1) and
register 0x2E (CSMA_SEED_1).
As long as a short address has not been set, only broadcast frames and frames matching the
IEEE address can be received.
Configuration examples for different device operating modes and handling of various frame
types can be found in Section 7.2.3.1 “Description of RX_AACK Configuration Bits” on page 54.
TX_ARET configuration steps:
• Leave register bit TX_AUTO_CRC_ON = 1
register 0x04, TRX_CTRL_1
• Configure CSMA-CA
– MAX_FRAME_RETRIES
register 0x2C, XAH_CTRL_0
– MAX_CSMA_RETRIES
register 0x2C, XAH_CTRL_0
– CSMA_SEED
registers 0x2D, 0x2E
– MAX_BE, MIN_BE
register 0x2F, CSMA_BE
• Configure CCA (see Section 8.5)
M A X _ F R A M E _ R E T R IE S ( re g i s te r 0 x 2 C) d e fi n e s t h e m a x i m u m n u m b e r o f f ra m e
retransmissions.
The register bits MAX_CSMA_RETRIES (register 0x2C) configure the number of CSMA-CA
retries after a busy channel is detected.
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The CSMA_SEED_0 and CSMA_SEED_1 register bits (registers 0x2D, 0x2E) define a random
seed for the back-off-time random-number generator in the AT86RF231.
The MAX_BE and MIN_BE register bits (register 0x2F) sets the maximum and minimum CSMA
back-off exponent (according to [1]).
7.2.3
RX_AACK_ON - Receive with Automatic ACK
The general functionality of the RX_AACK procedure is shown in Figure 7-9 on page 53.
The gray shaded area is the standard flow of an RX_AACK transaction for IEEE 802.15.4 compliant frames, refer Section 7.2.3.2 “Configuration of IEEE Scenarios” on page 55. All other
procedures are exceptions for specific operating modes or frame formats, refer to Section
7.2.3.3 “Configuration of non IEEE 802.15.4 Compliant Scenarios” on page 58.
The frame filtering operations is described in detail in Section 7.2.3.5 “Frame Filtering” on page
61.
In RX_AACK_ON state, the radio transceiver listens for incoming frames. After detecting a valid
PHR, the radio transceiver parses the frame content of the MAC header (MHR), refer to Section
8.1.2 “MAC Protocol Layer Data Unit (MPDU)” on page 80.
Generally, at nodes, configured as a normal device or PAN coordinator, a frame is not indicated
if the frame filter does not match and the FCS is invalid. Otherwise, the interrupt IRQ_3
(TRX_END) is issued after the completion of the frame reception. The microcontroller can then
read the frame. An exception applies if promiscuous mode is enabled; see Section 7.2.3.2 “Configuration of IEEE Scenarios” on page 55, in that case an IRQ_3 (TRX_END) interrupt is issued,
even if the FCS fails.
If the content of the MAC addressing fields of the received frame (refer to IEEE 802.15.4 section
7.2.1) matches one of the configured addresses, dependent on the addressing mode, an
address match interrupt IRQ_5 (AMI) is issued, refer to Section 7.2.3.5 “Frame Filtering” on
page 61. The expected address values are to be stored in registers 0x20 - 0x2B (Short address,
PAN-ID and IEEE address). Frame filtering as described in Section 7.2.3.5 “Frame Filtering” on
page 61 is also valid for Basic Operating Mode.
During reception the AT86RF231 parses bit [5] (ACK Request) of the frame control field of the
received data or MAC command frame to check if an ACK reply is expected. In that case and if
the frame passes the third level of filtering, see IEEE 802.15.4-2006, section 7.5.6.2, the radio
transceiver automatically generates and transmits an ACK frame.
The content of the frame pending subfield of the ACK response is set by register bit
AACK_SET_PD (register 0x2E, CSMA_SEED_1) when the ACK frame is sent in response to a
data request MAC command frame, otherwise this subfield is set to 0. The sequence number is
copied from the received frame.
Optionally, the start of the transmission of the acknowledgement frame can be influenced by
register bit AACK_ACK_TIME. Default value (according to standard IEEE 802.15.4) is 12 symbol times after the reception of the last symbol of a data or MAC command frame.
If the register bit AACK_DIS_ACK (register 0x2E, CSMA_SEED_1) is set, no acknowledgement
frame is sent even if an acknowledgment frame was requested. This is useful for operating the
MAC hardware accelerator in promiscuous mode, see Section 7.2.3.2 “Configuration of IEEE
Scenarios” on page 55.
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The status of the RX_AACK operation is indicated by register bits TRAC_STATUS (register
0x02, TRAC_STATUS), see Section 7.2.7 “Register Description - Control Registers” on page
68.
During the operations described above the AT86RF231 remains in BUSY_RX_AACK state.
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Figure 7-9.
Flow Diagram of RX_AACK
TRX_STATE = RX_AACK_ON
N
SHR detected
Y
TRX_STATE = BUSY_RX_AACK
Generate IRQ_2 (RX_START)
Scanning MHR
Frame Filtering
Note 1: Address match, Promiscuous Mode and
Reserved Frames:
- A radio transceiver in Promiscuous
Mode, or configured to receive Reserved
Frames handles received frames passing
the third level of filtering
- For details refer to the description of
Promiscuous Mode and Reserved
Frame Types
Promiscuous Mode
N
(see Note 1)
Y
Reserved Frames
Frame reception
Generate IRQ_5 (AMI)
AACK_PROM_MODE
== 1
Frame reception
N
Y
N
FCS valid
N
(see Note 2)
Note 2: FCS check is omitted for Promiscous Mode
Y
Y
Generate IRQ_3 (TRX_END)
N
N
ACK requested
Y
Y
N
N
Slotted Operation
== 0
AACK_ACK_TIME
== 0
AACK_ACK_TIME
== 0
Generate IRQ_3
(TRX_END)
N
Generate IRQ_3
(TRX_END)
Y
Y
Wait 6 symbol
periods
pin 11 (SLP_TR)
rising edge
FCS valid
Y
Y
Wait 2 symbol
periods
AACK_UPLD_RES_FT
== 1
(see Note 3)
Note 3: Additional conditions:
- ACK requested &
- ACK_DIS_ACK==0 &
- frame_version<=AACK_FVN_MODE
N
FCF[2:0]
>3
Wait 12 symbol
periods
Wait 2 symbol
periods
N
Y
Transmit ACK
TRX_STATE = RX_AACK_ON
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7.2.3.1
Description of RX_AACK Configuration Bits
Overview
Table 7-5 on page 54 summarizes all register bits which affect the behavior of an RX_AACK
transaction. For address filtering it is further required to setup address registers to match to the
expected address.
Configuration and address bits are to be set in TRX_OFF or PLL_ON state prior to switching to
RX_AACK mode.
A graphical representation of various operating modes is illustrated in Figure 7-9 on page 53.
Table 7-5.
Overview of RX_AACK Configuration Bits
Register
Register
Address
Bits
0x20,0x21
0x22,0x23
0x24
...........
0x2B
Register Name
Description
SHORT_ADDR_0/1
PAN_ADDR_0/1
IEEE_ADDR_0
........
IEEE_ADDR_7
Set node addresses
0x0C
7
RX_SAFE_MODE
Protect buffer after frame receive
0x17
1
AACK_PROM_MODE
Support promiscuous mode
0x17
2
AACK_ACK_TIME
Change auto acknowledge start time
0x17
4
AACK_UPLD_RES_FT
Enable reserved frame type reception, needed
to receive non-standard compliant frames
0x17
5
AACK_FLTR_RES_FT
Filter reserved frame types like data frame
type, needed for filtering of non-standard
compliant frames
0x2C
0
SLOTTED_OPERATION
If set, acknowledgment transmission has to be
triggered by pin 11 (SLP_TR)
0x2E
3
AACK_I_AM_COORD
If set, the device is a PAN coordinator
0x2E
4
AACK_DIS_ACK
Disable generation of acknowledgment
0x2E
5
AACK_SET_PD
Set frame pending subfield in Frame Control
Field (FCF), refer to Section 8.1.2.2
0x2E
7:6
AACK_FVN_MODE
Controls the ACK behavior, depending on FCF
frame version number
The usage of the RX_AACK configuration bits for various operating modes of a node is
explained in the following sections. Configuration bits not mentioned in the following two sections should be set to their reset values according to Table 14-1 on page 170.
All registers mentioned in Table 7-5 on page 54 are described in Section 7.2.6 “Register Summary” on page 68.
Note, that the general behavior of the "AT86RF231 Extended Feature Set", Section 11.
“AT86RF231 Extended Feature Set” on page 128, settings:
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• OQPSK_DATA_RATE
(PSDU data rate)
• SFD_VALUE
(alternative SFD value)
• ANT_DIV
(Antenna Diversity)
• RX_PDT_LEVEL
(blocking frame reception of lower power signals)
are completely independent from RX_AACK mode. Each of these operating modes can be combined with the RX_AACK mode.
7.2.3.2
Configuration of IEEE Scenarios
Normal Device
Table 7-6 on page 55 shows a typical RX_AACK configuration of an IEEE 802.15.4 device operating as a normal device, rather than a PAN coordinator or router.
Table 7-6.
Configuration of IEEE 802.15.4 Devices
Register
Register
Address
Bits
0x20,0x21
0x22,0x23
0x24,
...........
0x2B
Register Name
Description
SHORT_ADDR_0/1
PAN_ADDR_0/1
IEEE_ADDR_0
........
IEEE_ADDR_7
Set node addresses
0x0C
7
RX_SAFE_MODE
0: disable frame protection
1: enable frame protection
0x2C
0
SLOTTED_OPERATION
0: if transceiver works in unslotted mode
1: if transceiver works in slotted mode
0x2E
7:6
AACK_FVN_MODE
Controls the ACK behavior, depending on FCF
frame version number
0x00: acknowledges only frames with version
number 0, i.e. according to IEEE 802.15.4-2003
frames
0x01: acknowledges only frames with version
number 0 or 1, i.e. frames according to IEEE
802.15.4-2006
0x10: acknowledges only frames with version
number 0 or 1 or 2
0x11: acknowledges all frames, independent of
the FCF frame version number
Notes
• If no short address has been configured before the device has been assigned one by the
PAN-coordinator, only frames directed to either the broadcast address or the IEEE address
are received.
• In IEEE 802.15.4-2003 standard the frame version subfield did not yet exist but was marked
as reserved. According to this standard, reserved fields have to be set to zero. On the other
hand, IEEE 802.15.4-2003 standard requires ignoring reserved bits upon reception. Thus,
there is a contradiction in the standard which can be interpreted in two ways:
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1.
If a network should only allow access to nodes which use the IEEE 802.15.4-2003,
then AACK_FVN_MODE should be set to 0.
2.
If a device should acknowledge all frames independent of its frame version,
AACK_FVN_MODE should be set to 3. However, this can result in conflicts with
co-existing IEEE 802.15.4-2006 standard compliant networks.
The same holds for PAN coordinators, see Table 7-7 on page 56.
PAN-Coordinator
Table 7-7.
Configuration of a PAN Coordinator
Register
Register
Address
Bits
0x20,0x21
0x22,0x23
0x24,
...........
0x2B
Register Name
Description
SHORT_ADDR_0/1
PAN_ADDR_0/1
IEEE_ADDR_0
........
IEEE_ADDR_7
Set node addresses
0x0C
7
RX_SAFE_MODE
0: disable frame protection
1: enable frame protection
0x2C
0
SLOTTED_OPERATION
0: if transceiver works in unslotted mode
1: if transceiver works in slotted mode
0x2E
3
AACK_I_AM_COORD
1: device is PAN coordinator
0x2E
5
AACK_SET_PD
0: frame pending subfield is not set in FC
1: frame pending subfield is set in FCF
0x2E
7:6
AACK_FVN_MODE
Controls the ACK behavior, depending on FCF
frame version number
0x00: acknowledges only frames with version
number 0, i.e. according to IEEE 802.15.4-2003
frames
0x01: acknowledges only frames with version
number 0 or 1, i.e. frames according to IEEE
802.15.4-2006
0x10: acknowledges only frames with version
number 0 or 1 or 2
0x11: acknowledges all frames, independent of
the FCF frame version number
Promiscuous Mode
The promiscuous mode is described in IEEE 802.15.4-2006, section 7.5.6.2. This mode is further illustrated in Figure 7-9 on page 53. According to IEEE 802.15.4-2006 when in promiscuous
mode, the MAC sub layer shall pass received frames with correct FCS to the next higher layer
and shall not be processed further. That implies that frames should never be acknowledged.
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Only second level filter rules as defined by IEEE 802.15.4-2006, section 7.5.6.2, are applied to
the received frame.
Table 7-8 on page 57 shows the typical configuration of a device operating promiscuous mode.
Table 7-8.
Configuration of Promiscuous Mode
Register
Register
Address
Bits
0x20,0x21
0x22,0x23
0x24,
...
0x2B
Register Name
Description
SHORT_ADDR_0/1
PAN_ADDR_0/1
IEEE_ADDR_0
...
IEEE_ADDR_7
Address shall be set: 0x00
0x17
1
AACK_PROM_MODE
1: Enable promiscuous Mode
0x2E
4
AACK_DIS_ACK
1: Disable generation of acknowledgment
0x2E
7:6
AACK_FVN_MODE
Controls the ACK behavior, depending on FCF
frame version number
0x00: acknowledges only frames with version
number 0, i.e. according to IEEE 802.15.4-2003
frames
0x01: acknowledges only frames with version
number 0 or 1, i.e. frames according to
IEEE 802.15.4-2006
0x10: acknowledges only frames with version
number 0 or 1 or 2
0x11: acknowledges all frames, independent of
the FCF frame version number
If the radio transceiver is in promiscuous mode, second level of filtering according to
IEEE 802.15.4-2006, section 7.5.6.2, is applied to a received frame. However, an IRQ_3
(TRX_END) is issued even if the FCS is invalid. Thus, it is necessary to read register bit
RX_CRC_VALID (register 0x06, PHY_RSSI) after IRQ_3 (TRX_END) in order to verify the
reception of a frame with a valid FCS.
If a device, operating in promiscuous mode, receives a frame with a valid FCS which further
passed the third level of filtering according to IEEE 802.15.4-2006, section 7.5.6.2, an acknowledgement frame would be transmitted. According to the definition of the promiscuous mode a
received frame shall not be acknowledged, even if it is requested. Thus register bit
AACK_DIS_ACK (register 0x2E, CSMA_SEED_1) has to be set to 1.
In all receive modes an IRQ_5 (AMI) interrupt is issued, when the received frame matches the
node's address according to the filter rules described in Section 7.2.3.5 “Frame Filtering” on
page 61
Alternatively, in Basic Operating Mode RX_ON state, when a valid PHR is detected, an IRQ_2
(RX_START) is generated and the frame is received. The end of the frame reception is signalized with an IRQ_3 (TRX_END). At the same time the register bit RX_CRC_VALID (register
0x06, PHY_RSSI) is updated with the result of the FCS check (see Section 8.2 “Frame Check
Sequence (FCS)” on page 85). According to the promiscuous mode definition the
RX_CRC_VALID bit needs to be checked in order to dismiss corrupted frames.
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7.2.3.3
Configuration of non IEEE 802.15.4 Compliant Scenarios
Sniffer
Table 7-9 on page 58 shows an RX_AACK configuration to setup a sniffer device. Other
RX_AACK configuration bits, refer to Table 7-5 on page 54, should be set to their reset values.
All frames received are indicated by an IRQ_2 (RX_START) and IRQ_3 (TRX_END). After
frame reception register bit RX_CRC_VALID (register 0x06, PHY_RSSI) is updated with the
result of the FCS check (see Section 8.2 “Frame Check Sequence (FCS)” on page 85). The
RX_CRC_VALID bit needs to be checked in order to dismiss corrupted frames.
Table 7-9.
Configuration of a Sniffer Device
Register
Register
Register Name
Description
Address
Bits
0x17
1
AACK_PROM_MODE
1: Enable promiscuous Mode
0x2E
4
AACK_DIS_ACK
1: Disable generation of acknowledgment
This operating mode is similar to the promiscuous mode.
Reception of Reserved Frames
In RX_AACK mode, frames with reserved frame types, refer to Section 8.1.2.2 “Frame Control
Field (FCF)” on page 80, can also be handled. This might be required when implementing proprietary, non-standard compliant, protocols. It is an extension of the address filtering in RX_AACK
mode. Received frames are either handled similar to data frames, or may be allowed to completely bypass the address filter.
Table 7-10 on page 58 shows the required configuration for a node to receive reserved frames,
Figure 7-9 on page 53 shows the corresponding flow chart.
Table 7-10.
RX_AACK Configuration to Receive Reserved Frame Types
Register
Register
Address
Bits
0x20,0x21
0x22,0x23
0x24,
...........
0x2B
Register Name
Description
SHORT_ADDR_0/1
PAN_ADDR_0/1
IEEE_ADDR_0
........
IEEE_ADDR_7
Set node addresses
0x0C
7
RX_SAFE_MODE
0: disable frame protection
1: enable frame protection
0x17
4
AACK_UPLD_RES_FT
1: Enable reserved frame type reception
0x17
5
AACK_FLTR_RES_FT
Filter reserved frame types like data frame type,
see note below
0: disable
1: enable
0x2C
0
SLOTTED_OPERATION
0: if transceiver works in unslotted mode
1: if transceiver works in slotted mode
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Table 7-10.
RX_AACK Configuration to Receive Reserved Frame Types (Continued)
0x2E
3
AACK_I_AM_COORD
0: device is not PAN coordinator
1: device is PAN coordinator
0x2E
4
AACK_DIS_ACK
0: Enable generation of acknowledgment
1: Disable generation of acknowledgment
0x2E
7:6
AACK_FVN_MODE
Controls the ACK behavior, depending on FCF
frame version number
0x00: acknowledges only frames with version
number 0, i.e. according to IEEE 802.15.4-2003
frames
0x01: acknowledges only frames with version
number 0 or 1, i.e. frames according to
IEEE 802.15.4-2006
0x10: acknowledges only frames with version
number 0 or 1 or 2
0x11: acknowledges all frames, independent of
the FCF frame version number
There are two different options for handling reserved frame types.
1.
AACK_UPLD_RES_FT = 1, AACK_FLT_RES_FT = 0:
Any non-corrupted frame with a reserved frame type is indicated by an
IRQ_3 (TRX_END) interrupt. No further address filtering is applied on those frames. An
IRQ_5 (AMI) interrupt is never generated and the acknowledgment subfield is ignored.
2.
AACK_UPLD_RES_FT = 1, AACK_FLT_RES_FT = 1:
If AACK_FLT_RES_FT = 1 any frame with a reserved frame type is filtered by the
address filter similar to a data frame as described in the standard. This implies the
generation of the IRQ_5 (AMI) interrupts upon address match. An IRQ_3 (TRX_END)
interrupt is only generated if the address matched and the frame was not corrupted. An
acknowledgment is only send, when the ACK request subfield was set in the received
frame and an IRQ_3 (TRX_END) interrupt occurred.
3.
AACK_UPLD_RES_FT = 0:
Any received frame indicated as a reserved frame is discarded.
Short Acknowledgment Frame (ACK) Start Timing
Register bit AACK_ACK_TIME (register 0x17, XAH_CTRL_1), see Table 7-11 on page 60,
defines the symbol time between frame reception and transmission of an acknowledgment
frame.
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Table 7-11.
Overview of RX_AACK Configuration Bits
Register
Register
Address
Bit
0x17
2
Register Name
Description
AACK_ACK_TIME
0: Standard compliant acknowledgement timing
of 12 symbol periods. In slotted acknowledgement operation mode, the acknowledgment
frame transmission can be triggered 6 symbol
periods after reception of the frame earliest.
1: Reduced acknowledgment timing of 2 symbol
periods (32 µs).
Note that this feature can be used in all scenarios, independent of other configurations. However, shorter acknowledgment timing is especially useful when using High Data Rate Modes to
increase battery lifetime and to improve the overall data throughput; refer to Section 11.3 “High
Data Rate Modes” on page 137.
7.2.3.4
RX_AACK_NOCLK - RX_AACK_ON without CLKM
If the AT86RF231 is listening for an incoming frame and the microcontroller is not running an
application, the microcontroller can be powered down to decrease the total system power consumption. This special power-down scenario for systems running in clock synchronous mode
(see Section 6. “Microcontroller Interface” on page 16) is supported by the AT86RF231 using the
state RX_AACK_ON_NOCLK. The radio transceiver functionality in this state is based on that in
state RX_AACK_ON with pin 17 (CLKM) disabled.
The RX_AACK_NOCLK state is entered from RX_AACK_ON by a rising edge at pin 11
(SLP_TR). The return to RX_AACK_ON state results either from a successful frame reception or
a falling edge on pin SLP_TR.
The CLKM pin is disabled 35 clock cycles after the rising edge at SLP_TR pin. This allows the
microcontroller to complete its power-down sequence. This is not valid for clock rates 250 kHz
and 62.5 kHz, where the main clock at pin 17 (CLKM) is switched off immediately.
In case of the reception of a valid frame, IRQ_3 (TRX_END) is issued and pin 17 (CLKM) is
turned on. A timing diagram is shown in Figure 6-16 on page 28. A received frame is considered
valid if it passes address filtering and has a correct FCS. If an ACK was requested the radio
transceiver enters BUSY_RX_AACK state and follows the procedure described in Section 7.2.3
“RX_AACK_ON - Receive with Automatic ACK” on page 51.
After the transaction has been completed, the radio transceiver reenters the RX_AACK_ON
state.
The radio transceiver reenters the RX_AACK_ON_NOCLK state only, when the next rising edge
at SLP_TR pin occurs.
It is not recommended to operate the receiver in state RX_AACK_NOCLK with register bit
SLOTTED_OPERATION (register 0x2C, XAH_XTRL_0) set, refer to “Register Description Control Registers” on page 68.
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7.2.3.5
Frame Filtering
Frame Filtering is an evaluation whether or not a received frame is dedicated for this node. To
accept a received frame and to generate an address match interrupt IRQ_5 (AMI) a filtering procedure as described in IEEE 802.15.4-2006, section 7.5.6.2 (Third level of filtering) is applied to
the frame. The AT86RF231 RX_AACK mode accepts only frames that satisfy all of the following
requirements (quote from IEEE 802.15.4-2006, section 7.5.6.2):
1.
The Frame Type subfield shall not contain a reserved frame type.
2.
The Frame Version subfield shall not contain a reserved value.
3.
If a destination PAN identifier is included in the frame, it shall match macPANId or shall
be the broadcast PAN identifier (0xFFFF).
4.
If a short destination address is included in the frame, it shall match either
macShortAddress or the broadcast address (0xFFFF). Otherwise, if an extended
destination address is included in the frame, it shall match aExtendedAddress.
5.
If the frame type indicates that the frame is a beacon frame, the source PAN identifier
shall match macPANId unless macPANId is equal to 0xFFF, in which case the beacon
frame shall be accepted regardless of the source PAN identifier.
6.
If only source addressing fields are included in a data or MAC command frame, the
frame shall be accepted only if the device is the PAN coordinator and the source PAN
identifier matches macPANId.
The AT86RF231 requires satisfying two additional rules:
7.
The frame type indicates that the frame is not an ACK frame (refer to Table 8-4 on page
82).
8.
At least one address field must be configured.
Address match, indicated by interrupt IRQ_5 (AMI), is further controlled by the content of subfields of the frame control field of a received frame according to the following rule:
If (Destination Addressing Mode = 0 OR 1) AND (Source Addressing Mode = 0) no IRQ_5 (AMI)
is generated, refer to Section 8.1.2.2 “Frame Control Field (FCF)” on page 80. This effectively
causes all acknowledgement frames not to be announced, which otherwise always pass the filter, regardless of whether they are intended for this device or not.
For backward compatibility to IEEE 802.15.4-2003 third level filter rule 2 (Frame Version) can be
disabled by register bits AACK_FVN_MODE (register 0x2E, CSMA_SEED_1).
Frame filtering is available in Extended and Basic Operating Mode, refer to Section 7.1 “Basic
Operating Mode” on page 33, a frame passing the frame filtering generates an IRQ_5 (AMI), if
enabled.
Notes
• Filter rule 1 is affected by register bits AACK_FLTR_RES_FT and AACK_UPLD_RES_FT,
Section 7.2.7 “Register Description - Control Registers” on page 68.
• Filter rule 2 is affected by register bits AACK_FVN_MODE, Section 7.2.7 “Register
Description - Control Registers” on page 68.
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7.2.3.6
RX_AACK Slotted Operation - Slotted Acknowledgement
AT86RF231 supports slotted acknowledgement operation, refer to IEEE 802.15.4-2006, section
7.5.6.4.2, in conjunction with the microcontroller.
In RX_AACK mode with register bit SLOTTED_OPERATION (register 0x2C, XAH_CTRL_0) set,
the transmission of an acknowledgement frame has to be controlled by the microcontroller. If an
ACK frame has to be transmitted, the radio transceiver expects a rising edge on pin 11
(SLP_TR) to actually start the transmission. This waiting state is signaled 6 symbol periods after
the reception of the last symbol of a data or MAC command frame by register bits
TRAC_STATUS (register 0x02, XAH_CTRL_0), which are set to SUCCESS_WAIT_FOR_ACK
in that case. In networks using slotted operation the start of the acknowledgment frame, and
thus the exact timing, must be provided by the microcontroller.
A timing example of an RX_AACK transaction with register bit SLOTTED_OPERATION (register
0x2C, XAH_CTRL_0) set is shown in Figure 7-10 on page 62. The acknowledgement frame is
ready to transmit 6 symbol times after the reception of the last symbol of a data or MAC command frame. The transmission of the acknowledgement frame is initiated by the microcontroller
with the rising edge of pin 11 (SLP_TR) and starts tTR10 = 16 µs later. The interrupt latency tIRQ is
specified in Section 12.4 “Digital Interface Timing Characteristics” on page 157, parameter
12.4.17.
Figure 7-10. Example Timing of an RX_AACK Transaction for Slotted Operation
64
Frame Type
512
SFD
TRX_STATE
Data Frame (Length = 10, ACK=1)
BUSY_RX_AACK
tIRQ
96 µs
(6 symbols)
waiting period signalled by register bits TRAC_STATUS
SLP_TR
RX
RX/TX
TX
TX
TRX_END
Typ. Processing Delay
time [µs]
RX_AACK_ON
RX
IRQ
1026
ACK Frame
RX_AACK_ON
RX/TX
704
Frame
on Air
0
ACK transmission initated by microcontroller
SLP_TR
tTR10
If register bit AACK_ACK_TIME (register 0x17, XAH_CTRL_1) is set, an acknowledgment frame
can be sent already 2 symbol times after the reception of the last symbol of a data or MAC command frame.
7.2.3.7
RX_AACK Mode Timing
A timing example of an RX_AACK transaction is shown in Figure 7-11 on page 63. In this example a data frame of length 10 with an ACK request is received. The AT86RF231 changes to state
BUSY_RX_AACK after SFD detection. The completion of the frame reception is indicated by a
TRX_END interrupt. Interrupts IRQ_2 (RX_START) and IRQ_5 (AMI) are disabled in this example. The ACK frame is automatically transmitted after a default wait period of 12 symbols
(192 µs), register bit AACK_ACK_TIME = 0 (reset value). The interrupt latency tIRQ is specified
in Section 12.4 “Digital Interface Timing Characteristics” on page 157, parameter 12.4.17.
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Figure 7-11. Example Timing of an RX_AACK Transaction
Frame Type
TRX_STATE
RX/TX
512
SFD
Data Frame (Length = 10, ACK=1)
1088
time [µs]
ACK Frame
RX_AACK_ON
BUSY_RX_AACK
RX
RX_AACK_ON
TX
IRQ
Typ. Processing Delay
704
Frame
on Air
64
TRX_END
RX
RX/TX
0
tIRQ
192 µs
(12 symbols)
If register bit AACK_ACK_TIME (register 0x17, XAH_CTRL_1) is set, an acknowledgment frame
is sent already 2 symbol times after the reception of the last symbol of a data or MAC command
frame.
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7.2.4
TX_ARET_ON - Transmit with Automatic Retry and CSMA-CA Retry
Figure 7-12. Flow Diagram of TX_ARET
TRX_STATE = TX_ARET_ON
frame_rctr = 0
N
Start TX
Y
TRX_STATE = BUSY_TX_ARET
TRAC_STATUS = INVALID
(see Note 1)
N
Note 1: If MAX_CSMA_RETRIES = 7 no retry is
performed
MAX_CSMA_RETRIES
<7
Y
csma_rctr = 0
Random Back-Off
csma_rctr = csma_rctr + 1
CCA
N
CCA
Result
Failure
csma_rctr >
MAX_CSMA_RETRIES
Y
Success
Transmit Frame
frame_rctr = frame_rctr + 1
ACK requested
N
Y
N
Receive ACK
until timeout
Y
ACK valid
Y
N
N
frame_rctr >
MAX_FRAME_RETRIES
Y
TRAC_STATUS =
NO_ACK
Data Pending
N
Y
TRAC_STATUS =
SUCCESS_DATA_PENDING
TRAC_STATUS =
SUCCESS
TRAC_STATUS =
CHANNEL_ACCESS_FAILURE
Issue IRQ_3 (TRX_END) interrupt
TRX_STATE = TX_ARET_ON
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Overview
The implemented TX_ARET algorithm is shown in Figure 7-12 on page 64.
In TX_ARET mode, the AT86RF231 first executes the CSMA-CA algorithm, as defined by
IEEE 802.15.4-2006, section 7.5.1.4, initiated by a transmit start event. If the channel is IDLE a
frame is transmitted from the Frame Buffer. If the acknowledgement frame is requested the radio
transceiver additionally checks for an ACK reply.
The completion of the TX_ARET transmit transaction is indicated by an IRQ_3 (TRX_END)
interrupt.
Description
Configuration and address bits are to be set in TRX_OFF or PLL_ON state prior to switching to
TX_ARET mode. It is further recommended to transfer the PSDU data to the Frame Buffer in
advance. The transaction is started by either using pin 11 (SLP_TR), refer to Section 6.5
“Sleep/Wake-up and Transmit Signal (SLP_TR)” on page 27, or writing a TX_START command
to register 0x02 (TRX_STATE).
If the CSMA-CA detects a busy channel, it is retried as specified by the register bits
MAX_CSMA_RETRIES (register 0x2C, XAH_CTRL_0). In case that CSMA-CA does not detect
a clear channel after MAX_CSMA_RETRIES, it aborts the TX_ARET transaction, issues interrupt IRQ_3 (TRX_END), and set the value of the TRAC_STATUS register bits to
CHANNEL_ACCESS_FAILURE.
During transmission of a frame the radio transceiver parses bit 5 (ACK Request) of the MAC
header (MHR) frame control field of the PSDU data (PSDU octet #1) to be transmitted to check if
an ACK reply is expected.
If an ACK is expected, the radio transceiver automatically switches into receive mode to wait for
a valid ACK reply. After receiving an ACK frame the Frame Pending subfield of that frame is
parsed and the status register bits TRAC_STATUS are updated accordingly, refer to Table 7-12
on page 66. This receive procedure does not overwrite the Frame Buffer content. Transmit data
in the Frame Buffer is not changed during the entire TX_ARET transaction. Received frames
other than the expected ACK frame are discarded.
If no valid ACK is received or after timeout of 54 symbol periods (864 µs), the radio transceiver
retries the entire transaction, (including CSMA-CA) until the maximum number of retransmissions (as set by the register bits MAX_FRAME_RETRIES in register 0x2C (XAH_CTRL_0) is
exceeded.
After that, the microcontroller may read the value of the register bits TRAC_STATUS (register
0x02, TRX_STATE) to verify whether the transaction was successful or not. The register bits are
set according to the following cases, additional exit codes are described in Section 7.2.6 “Register Summary” on page 68:
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Table 7-12.
Value
Interpretation of TRAC_STATUS register bits
Name
Description
0
SUCCESS
The transaction was responded by a valid ACK, or, if no
ACK is requested, after a successful frame transmission
1
SUCCESS_DATA_PENDING
Equivalent to SUCCESS, indicates pending frame data
according to the MHR frame control field of the received
ACK response
3
CHANNEL_ACCESS_FAILURE
Channel is still busy after MAX_CSMA_RETRIES of
CSMA-CA
5
NO_ACK
No acknowledgement frames were received during all retry
attempts
7
INVALID
Entering TX_ARET mode sets TRAC_STATUS = 7
Note that if no ACK is expected (according to the content of the received frame in the Frame
Buffer), the radio transceiver issues IRQ_3 (TRX_END) directly after the frame transmission has
been completed. The value of register bits TRAC_STATUS (register 0x02, TRX_STATE) is set
to SUCCESS.
A value of MAX_CSMA_RETRIES = 7 initiates an immediate TX_ARET transaction without performing CSMA-CA. This is required to support slotted acknowledgement operation. Further the
value MAX_FRAME_RETRIES is ignored and the TX_ARET transaction is performed only once.
A timing example of a TX_ARET transaction is shown in Figure 7-13 on page 66.
Figure 7-13. Example Timing of a TX_ARET Transaction
FrameType
x
Data Frame (Length = 10, ACK=1)
TX_ARET_ON
RX/TX
ACK Frame
BUSY_TX_ARET
TX_ARET_ON
RX
TX
CSMA-CA
time [µs]
x+352
RX/TX
TRX_STATE
672
Frame
on Air
128
0
SLP_TR
IRQ
Typ. Processing Delay
TRX_END
tCSMA-CA
Note:
16 µs
32 µs
tIRQ
tCSMA-CA defines the random CSMA-CA processing time
Here an example data frame of length 10 with an ACK request is transmitted, see Table 7-13 on
page 67. After that the AT86RF231 switches to receive mode and expects an acknowledgement
response. During the whole transaction including frame transmit, wait for ACK and ACK receive
the radio transceiver status register TRX_STATUS (register 0x01, TRX_STATUS) signals
BUSY_TX_ARET.
A successful reception of the acknowledgment frame is indicated by IRQ_3 (TRX_END). The
status register TRX_STATUS (register 0x01, TRX_STATUS) changes back to TX_ARET_ON.
The TX_ARET status register TRAC_STATUS changes as well to TRAC_STATUS = SUCCESS
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or TRAC_STATUS = SUCCESS_DATA_PENDING if the frame pending subfield of the received
ACK frame was set to 1.
7.2.5
Interrupt Handling
The interrupt handling in the Extended Operating Mode is similar to the Basic Operating Mode,
refer to Section 7.1.3 “Interrupt Handling” on page 38. The microcontroller enables interrupts by
setting the appropriate bit in register 0x0E (IRQ_MASK).
For RX_AACK and TX_ARET the following interrupts inform about the status of a frame reception and transmission:
Table 7-13.
Interrupt Handling in Extended Operating Mode
Mode
Interrupt
Description
RX_AACK
IRQ_2 (RX_START)
Indicates a PHR reception
IRQ_5 (AMI)
Issued at address match
IRQ_3 (TRX_END)
Signals completion of RX_AACK transaction if successful
-
A received frame must pass the address filter
-
The FCS is valid
TX_ARET
IRQ_3 (TRX_END)
Signals completion of TX_ARET transaction
Both
IRQ_0 (PLL_LOCK)
Entering RX_AACK_ON or TX_ARET_ON state from
TRX_OFF state, the PLL_LOCK interrupt signals that the
transaction can be started
RX_AACK
For RX_AACK it is recommended to enable IRQ_3 (TRX_END). This interrupt is issued only if a
frame passes the frame filtering, refer to Section 7.2.3.5 “Frame Filtering” on page 61 and has a
valid FCS. This is in contrast to Basic Operating Mode, refer to Section 7.1.3 “Interrupt Handling”
on page 38. The use of the other interrupts is optional.
On reception of a valid PHR an IRQ_2 (RX_START) is issued. IRQ_5 (AMI) indicates address
match, refer to filter rules in Section 7.2.3.5 “Frame Filtering” on page 61, and the completion of
a frame reception with a valid FCS is indicated by interrupt IRQ_3 (TRX_END).
Thus, it can happen that an IRQ_2 (RX_START) and/or IRQ_5 (AMI) are issued, but no IRQ_3
(TRX_END) interrupt.
TX_ARET
In TX_ARET interrupt IRQ_3 (TRX_END) is only issued after completing the entire TX_ARET
transaction.
Acknowledgement frames do not issue IRQ_5 (AMI) or IRQ_3 (TRX_END) interrupts.
All other interrupts as described in Section 6.6 “Interrupt Logic” on page 29, are also available in
Extended Operating Mode.
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7.2.6
Register Summary
The following registers are to be configured to control the Extended Operating Mode:
Table 7-14.
Register Summary
Reg.-Addr
Register Name
Description
0x01
TRX_STATUS
Radio transceiver status, CCA result
0x02
TRX_STATE
Radio transceiver state control, TX_ARET status
0x04
TRX_CTRL_1
TX_AUTO_CRC_ON
0x08
PHY_CC_CCA
CCA mode control, see Section 8.5.6
0x09
CCA_THRES
CCA threshold settings, see Section 8.5.6
0x17
XAH_CTRL_1
RX_AACK control
0x20 - 0x2B
7.2.7
Address filter configuration
Short address, PAN-ID and IEEE address
0x2C
XAH_CTRL_0
TX_ARET control, retries value control
0x2D
CSMA_SEED_0
CSMA-CA seed value
0x2E
CSMA_SEED_1
CSMA-CA seed value, RX_AACK control
0x2F
CSMA_BE
CSMA-CA back-off exponent control
Register Description - Control Registers
Register 0x01 (TRX_STATUS):
The read-only register TRX_STATUS signals the present state of the radio transceiver as well
as the status of a CCA application. A state change is initiated by writing a state transition command to register bits TRX_CMD (register 0x02, TRX_STATE).
Bit
7
6
5
CCA_DONE
CCA_STATUS
Reserved
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
+0x01
4
3
2
1
0
TRX_STATUS
TRX_STATUS
• Bit 7 - CCA_DONE
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94, not updated in Extended
Operating Mode.
• Bit 6 - CCA_STATUS
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94, not updated in Extended
Operating Mode.
• Bit 5 - Reserved
• Bit [4:0] - TRX_STATUS
The register bits TRX_STATUS signal the current radio transceiver status.
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Table 7-15.
Radio Transceiver Status
Register Bit
Value
State Description
TRX_STATUS
0x00
P_ON
0x01
BUSY_RX
0x02
BUSY_TX
0x06
RX_ON
0x08
TRX_OFF (CLK Mode)
0x09
PLL_ON (TX_ON)
0x0F
(1)
SLEEP
0x11
BUSY_RX_AACK
0x12
BUSY_TX_ARET
0x16
RX_AACK_ON
0x19
TX_ARET_ON
0x1C
RX_ON_NOCLK
0x1D
RX_AACK_ON_NOCLK
0x1E
BUSY_RX_AACK_NOCLK
0x1F(2)
STATE_TRANSITION_IN_PROGRESS
All other values are reserved
Notes:
1. In SLEEP state register not accessible.
2. Do not try to initiate a further state change while the radio transceiver is in
STATE_TRANSITION_IN_PROGRESS state.
Register 0x02 (TRX_STATE):
The AT86RF231 radio transceiver states are controlled via register TRX_STATE using register
bits TRX_CMD. The read-only register bits TRAC_STATUS indicate the status or result of an
Extended Operating Mode transaction.
A successful state transition shall be confirmed by reading register bits TRX_STATUS (register
0x01, TRX_STATUS).
Register bits TRX_CMD are used for Extended and Basic Operating Mode, refer to Section 7.1
“Basic Operating Mode” on page 33.
Bit
7
+0x02
6
5
4
3
TRAC_STATUS
2
1
0
TRX_CMD
TRX_STATE
Read/Write
R
R
R
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
• Bit [7:5] - TRAC_STATUS
The status of the RX_AACK and TX_ARET procedure is indicated by register bits
TRAC_STATUS. Details of the algorithm and a description of the status information are given in
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Section 7.2.3 “RX_AACK_ON - Receive with Automatic ACK” on page 51 and Section 7.2.4
“TX_ARET_ON - Transmit with Automatic Retry and CSMA-CA Retry” on page 64.
Table 7-16.
TRAC_STATUS Transaction Status
Register Bits
Value
TRAC_STATUS
0(1)
Description
SUCCESS
RX_AACK
TX_ARET
X
X
1
SUCCESS_DATA_PENDING
2
SUCCESS_WAIT_FOR_ACK
3
CHANNEL_ACCESS_FAILURE
X
5
NO_ACK
X
(1)
INVALID
7
X
X
X
X
All other values are reserved
Notes:
1. Even though the reset value for register bits TRAC_STATUS is 0, the RX_AACK and
TX_ARET procedures set the register bits to TRAC_STATUS = 7 (INVALID) when it is started.
TX_ARET
SUCCESS_DATA_PENDING:
Indicates a successful reception of an ACK frame with
frame pending bit set to 1.
RX_AACK
SUCCESS_WAIT_FOR_ACK:
Indicates an ACK frame is about to sent in RX_AACK
slotted acknowledgement. Slotted acknowledgement
operation
must
be
enabled
with
register
bit
SLOTTED_OPERATION (register 0x2C, XAH_XTRL_0).
The microcontroller must pulse pin 11 (SLP_TR) at the next
back-off slot boundary in order to initiate a transmission of
the ACK frame. For details refer to IEEE 802.15.4-2006,
section 7.5.6.4.2.
• Bit [4:0] - TRX_CMD
A write access to register bits TRX_CMD initiate a radio transceiver state transition:
Table 7-17.
State Control Register
Register Bit
Value
State Description
TRX_CMD
0x00
NOP
0x02
TX_START
0x03
FORCE_TRX_OFF
0x04(1)(2)
FORCE_PLL_ON
0x06
RX_ON
0x08
TRX_OFF (CLK Mode)
0x09
PLL_ON (TX_ON)
0x16
RX_AACK_ON
0x19
TX_ARET_ON
All other values are reserved and mapped to NOP
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Notes:
1. FORCE_PLL_ON is not valid for states SLEEP, P_ON, RESET, TRX_OFF, and all *_NOCLK
states, as well as STATE_TRANSITION_IN_PROGRESS towards these states.
2. Using FORCE_PLL_ON to interrupt an TX_ARET transaction, it is recommended to check
register bits [7:5] of register address 0x32 for value 0. If this value is different, TRX_CMD
sequence FORCE_TRX_OFF shall be used immediately followed by TRX_CMD sequence
PLL_ON. This performs a state transition to PLL_ON.
Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
+0x04
3
2
1
0
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
0
0
0
SPI_CMD_MODE
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
Refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
If set, register bit TX_AUTO_CRC_ON enables the automatic FCS generation. For further
details refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
Register 0x17 (XAH_CTRL_1):
The XAH_CTRL_1 register is a control register for Extended Operating Mode.
Bit
7
+0x17
6
Reserved
5
4
3
2
1
0
AACK_FLTR_RES_FT
AACK_UPLD_RES_FT
Reserved
AACK_ACK_TIME
AACK_PROM_MODE
Reserved
Read/Write
R/W
R
R/W
R/W
R
R/W
R/W
R
Reset Value
0
0
0
0
0
0
0
0
XAH_CTRL_1
• Bit [7:6] - Reserved
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• Bit 5 - AACK_FLTR_RES_FT
This register bit shall only be set if AACK_UPLD_RES_FT = 1.
If AACK_FLTR_RES_FT = 1 reserved frame types are filtered similar to data frames as specified in IEEE 802.15.4-2006. Reserved frame types are explained in IEEE 802.15.4, section
7.2.1.1.1.
If AACK_FLTR_RES_FT = 0 the received reserved frame is only checked for a valid FCS.
• Bit 4 - AACK_UPLD_RES_FT
If AACK_UPLD_RES_FT = 1 received frames indicated as a reserved frame are further processed. For those frames, an IRQ_3 (TRX_END) interrupt is generated if the FCS is valid.
In conjunction with the configuration bit AACK_FLTR_RES_FT set, these frames are handled
like IEEE 802.15.4 compliant data frames during RX_AACK transaction. An IRQ_5 (AMI) interrupt is issued, if the addresses in the received frame match the node's addresses.
That means, if a reserved frame passes the third level filter rules, an acknowledgement frame is
generated and transmitted if it was requested by the received frame. If this is not wanted register
bit AACK_DIS_ACK (register 0x2E, CSMA_SEED_1) has to be set.
• Bit 3 - Reserved
• Bit 2 - AACK_ACK_TIME
According to IEEE 802.15.4, section 7.5.6.4.2, the transmission of an acknowledgment frame
shall commence 12 symbols (aTurnaroundTime) after the reception of the last symbol of a data
or MAC command frame. This is achieved with the reset value of the register bit
AACK_ACK_TIME.
Alternatively, if AACK_ACK_TIME = 1 an acknowledgment frame is sent already 2 symbol periods after the reception of the last symbol of a data or MAC command frame. This may be
applied to proprietary networks or networks using the High Data Rate Modes to increase battery
lifetime and to improve the overall data throughput; refer to Section 11.3 “High Data Rate
Modes” on page 137.
This setting affects also to acknowledgment frame response time for slotted acknowledgement
operation, see Section 7.2.3.6 “RX_AACK Slotted Operation - Slotted Acknowledgement” on
page 62.
• Bit 1 - AACK_PROM_MODE
Register bit AACK_PROM_MODE enables the promiscuous mode, within the RX_AACK mode;
refer to IEEE 802.15.4-2006, section 7.5.6.5.
If this bit is set, every incoming frame with a valid PHR finishes with IRQ_3 (TRX_END) interrupt
even if the third level filter rules do not match or the FCS is not valid. Register bit
RX_CRC_VALID (register 0x06, PHY_RSSI) is set accordingly.
Here, if a frame passes the third level filter rules, an acknowledgement frame is generated and
transmitted unless disabled by register bit AACK_DIS_ACK (register 0x2E, CSMA_SEED_1).
• Bit 0 - Reserved
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Register 0x2C (XAH_CTRL_0):
Register 0x2C (XAH_CTRL_0) is a control register for Extended Operating Mode.
Bit
7
+0x2C
6
5
4
3
MAX_FRAME_RETRIES
2
1
0
MAX_CSMA_RETRIES
SLOTTED_OPERATION
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
1
1
0
0
0
XAH_CTRL_0
• Bit [7:4] - MAX_FRAME_RETRIES
The setting of MAX_FRAME_RETRIES in TX_ARET mode specifies the number of attempts to
retransmit a frame, when it was not acknowledged by the recipient, before the transaction gets
cancelled.
• Bit [3:1] - MAX_CSMA_RETRIES
MAX_CSMA_RETRIES specifies the number of retries in TX_ARET mode to repeat the CSMACA procedure before the transaction gets cancelled. According IEEE 802.15.4 the valid range of
MAX_CSMA_RETRIES is [0, 1, …, 5].
A value of MAX_CSMA_RETRIES = 7 initiates an immediate frame transmission without performing CSMA-CA. This may especially be required for slotted acknowledgement operation.
MAX_CSMA_RETRIES = 6 is reserved.
• Bit 0 - SLOTTED_OPERATION
Using RX_AACK mode in networks operating in beacon or slotted mode, refer to IEEE 802.15.4
2006, section 5.5.1, register bit SLOTTED_OPERATION indicates that acknowledgement
frames are to be sent on back-off slot boundaries (slotted acknowledgement).
If this register bit is set the acknowledgement frame transmission has to be initiated by the
microcontroller using the rising edge of pin 11 (SLP_TR). This waiting state is signaled in sub
register TRAC_STATUS (register 0x02, TRX_STATE) with value SUCCESS_WAIT_FOR_ACK.
Table 7-18.
Register Bit Slotted Acknowledgement Operation
Register Bit
Value
SLOTTED_OPERATION
State Description
0
The radio transceiver operates in unslotted mode. An
acknowledgment frame is automatically sent if requested.
1
Refer to Section 7.2.3.6. The transmission of an
acknowledgement frame has to be controlled by the
microcontroller.
Register 0x2D (CSMA_SEED_0):
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
1
1
1
0
+0x2D
4
3
2
1
0
R/W
R/W
R/W
R/W
1
0
1
0
CSMA_SEED_0[7:0]
CSMA_SEED_0
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• Bit [7:0] - CSMA_SEED_0
This register contains the lower 8-bit of the CSMA_SEED, bits [7:0]. The higher 3 bit are part of
register bits CSMA_SEED_1 (register 0x2E, CSMA_SEED_1). CSMA_SEED is the seed for the
random number generation that determines the length of the back-off period in the CSMA-CA
algorithm.
It is recommended to initialize registers CSMA_SEED by random values. This can be done
using register bits RND_VALUE (register 0x06, PHY_RSSI), refer to Section 11.2 “Random
Number Generator” on page 136.
Register 0x2E (CSMA_SEED_1):
The CSMA_SEED_1 register is a control register for RX_AACK and contains a part of the
CSMA_SEED for the CSMA-CA algorithm.
Bit
7
6
5
4
3
AACK_SET_PD
AACK_DIS_ACK
AACK_I_AM_COORD
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
0
0
0
0
1
0
+0x2E
AACK_FVN_MODE
Read/Write
R/W
Reset Value
0
Note:
2
1
0
CSMA_SEED_1
CSMA_SEED_1
The register bits CSMA_SEED_0/1 content initializes the TX_ARET random backoff generator
after leaving SLEEP state. To prevent a reinitialization with the same value it is recommended to
reinitialize all register bits with random values before entering SLEEP state.
• Bit [7:6] - AACK_FVN_MODE
The frame control field of the MAC header (MHR) contains a frame version subfield. The setting
of AACK_FVN_MODE specifies the frame filtering behavior of the AT86RF231. According to the
content of these register bits the radio transceiver passes frames with a specific frame version
number, number group, or independent of the frame version number.
Thus the register bit AACK_FVN_MODE defines the maximum acceptable frame version.
Received frames with a higher frame version number than configured do not pass the address
filter and are not acknowledged.
Table 7-19.
Register Bit Slotted Acknowledgement Operation
Register Bit
AACK_FVN_MODE
Value
State Description
0
Acknowledge frames with version number 0
1
Acknowledge frames with version number 0 or 1
2
Acknowledge frames with version number 0 or 1 or 2
3
Acknowledge independent of frame version number
The frame version field of the acknowledgment frame is set to 0x00 according to IEEE 802.15.42006, section 7.2.2.3.1, Acknowledgment frame MHR fields.
• Bit 5 - AACK_SET_PD
The content of AACK_SET_PD bit is copied into the frame pending subfield of the acknowledgment frame if the ACK is the answer to a data request MAC command frame.
In addition, if register bits AACK_FVN_MODE (register 0x2E, CSMA_SEED_1) are configured
to accept frames with a frame version other than 0 or 1, the content of register bit
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AACK_SET_PD is also copied into the frame pending subfield of the acknowledgment frame for
any MAC command frame with a frame version of 2 or 3 that have the security enabled subfield
set to 1. This is done in the assumption that a future version of the standard [1] might change the
length or structure of the auxiliary security header, so it is not possible to safely detect whether
the MAC command frame is actually a data request command or not.
• Bit 4 - AACK_ DIS_ACK
If this bit is set no acknowledgment frames are transmitted in RX_AACK Extended Operating
Mode, even if requested.
• Bit 3 - AACK_I_AM_COORD
This register bit has to be set if the node is a PAN coordinator. It is used for address filtering in
RX_AACK.
If AACK_I_AM_COORD = 1 and if only source addressing fields are included in a data or MAC
command frame, the frame shall be accepted only if the device is the PAN coordinator and the
source PAN identifier matches macPANId, for details refer to IEEE 802.15.4, section 7.5.6.2
(third-level filter rule 6).
• Bit [2:0] - CSMA_SEED_1
These register bits are the higher 3-bit of the CSMA_SEED, bits [10:8]. The lower part is in register 0x2D (CSMA_SEED_0), see register CSMA_SEED_0 for details.
Register 0x2F (CSMA_BE):
Bit
7
6
5
4
3
2
MAX_BE
+0x2F
1
0
MIN_BE
CSMA_BE
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
1
0
1
0
0
1
1
• Bit [7:4] - MAX_BE
Register bits MAX_BE defines the maximum back-off exponent used in the CSMA-CA algorithm
to generate a pseudo random number for back off the CCA. For details refer to IEEE 802.15.42006, Section 7.5.1.4.
Valid values are [4'd8, 4'd7, … , 4'd3].
• Bit [3:0] - MIN_BE
Register bits MIN_BE defines the minimum back-off exponent used in the CSMA-CA algorithm
to generate a pseudo random number for back off the CCA. For details refer to IEEE 802.15.42006, Section 7.5.1.4.
Valid values are [MAX_BE, (MAX_BE - 1), … , 4'd0].
Note
• If MIN_BE = 0 and MAX_BE = 0 the CCA back off period is always set to 0.
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7.2.8
Register Description - Address Registers
Register 0x20 (SHORT_ADDR_0):
This register contains the lower 8 bit of the MAC short address for Frame Filter address recognition, bits [7:0].
Bit
7
6
5
+0x20
4
3
2
1
0
SHORT_ADDR_0[7:0]
SHORT_ADDR_0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
1
1
1
1
1
1
1
Register 0x21 (SHORT_ADDR_1):
This register contains the upper 8 bit of the MAC short address for Frame Filter address recognition, bits [15:8].
Bit
7
6
5
4
+0x21
3
2
1
0
SHORT_ADDR_1[7:0]
SHORT_ADDR_1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
1
1
1
1
1
1
1
Register 0x22 (PAN_ID_0):
This register contains the lower 8 bit of the MAC PAN ID for Frame Filter address recognition,
bits [7:0].
Bit
7
6
5
4
Read/Write
R/W
R/W
R/W
R/W
Reset Value
1
1
1
1
+0x22
3
2
1
0
R/W
R/W
R/W
R/W
1
1
1
1
PAN_ID_0[7:0]
PAN_ID_0
Register 0x23 (PAN_ID_1):
This register contains the upper 8 bit of the MAC PAN ID for Frame Filter address recognition,
bits [15:8].
Bit
7
6
5
4
Read/Write
R/W
R/W
R/W
R/W
Reset Value
1
1
1
1
+0x23
3
2
1
0
R/W
R/W
R/W
R/W
1
1
1
1
PAN_ID_1[7:0]
PAN_ID_1
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Register 0x24 (IEEE_ADDR_0):
This register contains the lower 8 bit of the MAC IEEE address for Frame Filter address recognition, bits [7:0].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x24
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_0[7:0]
IEEE_ADDR_0
Register 0x25 (IEEE_ADDR_1):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[15:8].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x25
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_1[7:0]
IEEE_ADDR_1
Register 0x26 (IEEE_ADDR_2):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[23:16].
Bit
7
6
5
+0x26
4
3
2
1
0
IEEE_ADDR_2[7:0]
IEEE_ADDR_2
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
Register 0x27 (IEEE_ADDR_3):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[31:24].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x27
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_3[7:0]
IEEE_ADDR_3
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Register 0x28 (IEEE_ADDR_4):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[39:32].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x28
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_4[7:0]
IEEE_ADDR_4
Register 0x29 (IEEE_ADDR_5):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[47:40].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x29
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_5[7:0]
IEEE_ADDR_5
Register 0x2A (IEEE_ADDR_6):
This register contains 8 bit of the MAC IEEE address for Frame Filter address recognition, bits
[55:48].
Bit
7
6
5
+0x2A
4
3
2
1
0
IEEE_ADDR_6[7:0]
IEEE_ADDR_6
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
Register 0x2B (IEEE_ADDR_7):
This register contains the most significant 8 bits of the MAC IEEE Frame Filter address for
address recognition, bits [63:56].
Bit
7
6
5
Read/Write
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
+0x2B
4
3
2
1
0
R/W
R/W
R/W
R/W
0
0
0
0
IEEE_ADDR_7[7:0]
IEEE_ADDR_7
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8. Functional Description
8.1
Introduction - IEEE 802.15.4 - 2006 Frame Format
Figure 8-1 on page 79 provides an overview of the physical layer (PHY) frame structure as
defined by IEEE 802.15.4. Figure 8-2 on page 80 shows the frame structure of the medium
access control (MAC) layer.
Figure 8-1.
IEEE 802.15.4 Frame Format - PHY-Layer Frame Structure (PPDU)
PHY Protocol Data Unit (PPDU)
Preamble Sequence
SFD
Frame Length
PHY Payload
5 octets
1 octet
max. 127 octets
Synchronization Header (SHR)
(PHR)
PHY Service Data Unit (PSDU)
MAC Protocol Data Unit (MPDU)
8.1.1
8.1.1.1
PHY Protocol Layer Data Unit (PPDU)
8.1.1.1 Synchronization Header (SHR)
The SHR consists of a four-octet preamble field (all zero), followed by a single byte start-offrame delimiter (SFD) which has the predefined value 0xA7. During transmit, the SHR is automatically generated by the AT86RF231, thus the Frame Buffer shall contain PHR and PSDU
only.
The transmission of the SHR requires 160 µs (10 symbols). As the SPI data rate is normally
higher than the over-air data rate, this allows the microcontroller to initiate a transmission without
having transferred the full frame data already. Instead it is possible to subsequently write the
frame content.
During frame reception, the SHR is used for synchronization purposes. The matching SFD
determines the beginning of the PHR and the following PSDU payload data.
8.1.1.2
PHY Header (PHR)
The PHY header is a single octet following the SHR. The least significant 7 bits denote the frame
length of the following PSDU, while the most significant bit of that octet is reserved, and shall be
set to 0 for IEEE 802.15.4 compliant frames.
On receive the PHR is returned as the first octet during Frame Buffer read access. Even though
the standard only defines frame lengths ≤127 bytes, AT86RF231 is able to transmit and receive
frame length values >127. For IEEE 802.15.4 compliant operation bit 7 has to be masked by
SW. The reception of a valid PHR is signaled by an interrupt IRQ_2 (RX_START).
On transmit the PHR is to be supplied by the microcontroller during Frame Buffer write access
as the first octet.
8.1.1.3
PHY Payload (PHY Service Data Unit, PSDU)
The PSDU has a variable length between 0 and aMaxPHYPacketSize (127, maximum PSDU
size in octets) whereas the last two octets are used for the Frame Check Sequence (FCS). The
length of the PSDU is signaled by the frame length field (PHR), refer to Table 8-1 on page 80.
The PSDU contains the MAC Protocol Layer Data Unit (MPDU).
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Received frames with a frame length field set to 0x00 (invalid PHR) are not signaled to the
microcontroller.
Table 8-1 on page 80 summarizes the type of payload versus the frame length value.
Table 8-1.
Frame Length Field - PHR
Frame Length Value
Payload
0-4
Reserved
5
MPDU (Acknowledgement)
6-8
Reserved
9 - aMaxPHYPacketSize
8.1.2
MPDU
MAC Protocol Layer Data Unit (MPDU)
Figure 8-2 on page 80 shows the frame structure of the MAC layer.
Figure 8-2.
IEEE 802.15.4 Frame Format - MAC-Layer Frame Structure (MPDU)
MAC Protocol Data Unit (MPDU)
Sequence
Number
FCF
Addressing Fields
MAC Payload
MAC Header (MHR)
Destination
PAN ID
0
1
2
Frame Type
Destination
Source
address
PAN ID
0/4/6/8/10/12/14/16/18/20 octets
3
4
5
Sec.
Enabled
Frame
Pending
ACK
Request
FCS
MAC Service Data Unit (MSDU)
6
7
Source
address
8
Auxiliary Security Header
CRC-16
0/5/6/10/14 octets
2 octets
9
Intra
Reserved
PAN
Frame Control Field 2 octets
(MFR)
10
11
Destination
addressing mode
12
13
14
Frame Version
15
Source
addressing mode
8.1.2.1
MAC Header (MHR) Fields
The MAC header consists of the Frame Control Field (FCF), a sequence number, and the
addressing fields (which are of variable length, and can even be empty in certain situations).
8.1.2.2
Frame Control Field (FCF)
The FCF consists of 16 bits, and occupies the first two octets of the MPDU or PSDU,
respectively.
Figure 8-3.
0
IEEE 802.15.4-2006 Frame Control Field (FCF)
1
Frame Type
2
3
4
5
6
Sec.
Enabled
Frame
Pending
ACK
Request
Intra
PAN
7
8
Reserved
9
10
11
Destination
addressing mode
12
13
Frame Version
14
15
Source
addressing mode
Frame Control Field 2 octets
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• Bit [2:0]:
describes the frame type. Table 8-2 on page 81 summarizes frame types defined by IEEE
802.15.4, section 7.2.1.1.1.
Table 8-2.
Frame Control Field - Frame Type Subfield
Frame Control Field Bit Assignments
Description
Frame Type Value
b2 b1 b0
Value
000
0
Beacon
001
1
Data
010
2
Acknowledge
011
3
MAC command
100 - 111
4-7
Reserved
This subfield is used for address filtering by the third level filter rules. Only frame types 0 - 3 pass
the third level filter rules, refer to Section 7.2.3.5 “Frame Filtering” on page 61 Automatic address
filtering by the AT86RF231 is enabled when using the RX_AACK mode, refer to Section 7.2.3
“RX_AACK_ON - Receive with Automatic ACK” on page 51.
However, a reserved frame (frame type value > 3) can be received if register bit
AACK_UPLD_RES_FT (register 0x17, XAH_CTRL_1) is set, for details refer to Section 7.2.3.3
“Configuration of non IEEE 802.15.4 Compliant Scenarios” on page 58.
Address filtering is also provided in Basic Operating Mode, refer to Section 7.1 “Basic Operating
Mode” on page 33.
• Bit 3:
indicates whether security processing applies to this frame.
• Bit 4:
is the "Frame Pending" subfield. This field can be set in an acknowledgment frame (ACK) in
response to a data request MAC command frame. This bit indicates that the node, which transmitted the ACK, has more data to send to the node receiving the ACK.
For acknowledgment frames automatically generated by the AT86RF231, this bit is set according to the content of register bit AACK_SET_PD in register 0x2E (CSMA_SEED_1) if the
received frame was a data request MAC command frame.
• Bit 5:
forms the "Acknowledgment Request" subfield. If this bit is set within a data or MAC command
frame that is not broadcast, the recipient shall acknowledge the reception of the frame within the
time specified by IEEE 802.15.4 (i.e. within 192 µs for non beacon-enabled networks).
The radio transceiver parses this bit during RX_AACK mode and transmits an acknowledgment
frame if necessary.
In TX_ARET mode this bit indicates if an acknowledgement frame is expected after transmitting
a frame. If this is the case, the receiver waits for the acknowledgment frame, otherwise the
TX_ARET transaction is finished.
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• Bit 6:
the "Intra-PAN" subfield indicates that in a frame, where both, the destination and source
addresses are present, the PAN-ID of the source address field is omitted. In RX_AACK mode,
this bit is evaluated by the address filter logic of the AT86RF231.
• Bit [11:10]:
the "Destination Addressing Mode" subfield describes the format of the destination address of
the frame. The values of the address modes are summarized in Table 8-3 on page 82, according
to IEEE 802.15.4.
Table 8-3.
Frame Control Field - Destination and Source Addressing Mode
Frame Control Field Bit Assignments
Description
Addressing Mode
b11 b10
b15 b14
Value
00
0
PAN identifier and address fields are not present
01
1
Reserved
10
2
Address field contains a 16-bit short address
11
3
Address field contains a 64-bit extended address
If the destination address mode is either 2 or 3 (i.e. if the destination address is present), it
always consists of a 16-bit PAN ID first, followed by either the 16-bit or 64-bit address as
described by the mode.
• Bit [13:12]:
the "Frame Version" subfield specifies the version number corresponding to the frame. These
register bits are reserved in IEEE 802.15.4-2003.
This subfield shall be set to 0 to indicate a frame compatible with IEEE 802.15.4-2003 and 1 to
indicate an IEEE 802.15.4-2006 frame. All other subfield values shall be reserved for future use.
RX_AACK register bit AACK_FVN_MODE (register 0x2E, CSMA_SEED_1) controls the behavior of frame acknowledgements. This register determines if, depending on the Frame Version
Number, a frame is acknowledged or not. This is necessary for backward compatibility to IEEE
802.15.4-2003 and for future use. Even if frame version numbers 2 and 3 are reserved, it can be
handled by the radio transceiver, for details refer to Section 7.2.7 “Register Description - Control
Registers” on page 68.
See IEEE 802.15.4-2006, section 7.2.3 for details on frame compatibility.
Table 8-4.
Frame Control Field - Frame Version Subfield
Frame Control Field Bit Assignments
Description
Frame Version
b13 b12
Value
00
0
Frames are compatible with IEEE 802.15.4 2003
01
1
Frames are compatible with IEEE 802.15.4-2006
10
2
Reserved
11
3
Reserved
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• Bit [15:14]:
the "Source Addressing Mode" subfield, with similar meaning as "Destination Addressing Mode",
see Table 8-3 on page 82.
The subfields of the FCF (Bits 0-2, 3, 6, 10-15) affect the address filter logic of the AT86RF231
while operating in RX_AACK operation, see Section 7.2.3 “RX_AACK_ON - Receive with Automatic ACK” on page 51.
8.1.2.3
Frame Compatibility between IEEE 802.15.4-2003 and IEEE 802.15.4-2006
All unsecured frames according to IEEE 802.15.4-2006 are compatible with unsecured frames
compliant with IEEE 802.15.4-2003 with two exceptions: a coordinator realignment command
frame with the "Channel Page" field present (see IEEE 802.15.4-2006, section 7.3.8) and any
frame with a MAC Payload field larger than aMaxMACSafePayloadSize octets.
Compatibility for secured frames is shown in Table 8-5 on page 83, which identifies the security
operating modes for IEEE 802.15.4-2006.
Table 8-5.
Frame Control Field - Security and Frame Version
Frame Control Field Bit Assignments
Description
Security Enabled
b3
Frame Version
b13 b12
0
00
No security. Frames are compatible between
IEEE 802.15.4-2003 and IEEE 802.15.4-2006.
0
01
No security. Frames are not compatible between
IEEE 802.15.4-2003 and IEEE 802.15.4-2006.
1
00
Secured frame formatted according to IEEE 802.15.4-2003.
This frame type is not supported in IEEE 802.15.4-2006.
1
01
Secured frame formatted according to IEEE 802.15.4-2006
8.1.2.4
Sequence Number
The one-octet sequence number following the FCF identifies a particular frame, so that duplicated frame transmissions can be detected. While operating in RX_AACK mode, the content of
this field is copied from the frame to be acknowledged into the acknowledgment frame.
8.1.2.5
Addressing Fields
The addressing fields of the MPDU are used by the AT86RF231 for address matching indication. The destination address (if present) is always first, followed by the source address (if
present). Each address field consists of the Intra PAN ID and a device address. If both
addresses are present, and the "Intra PAN-ID compression" subfield in the FCF is set to one, the
source Intra PAN ID is omitted.
Note that in addition to these general rules, IEEE 802.15.4 further restricts the valid address
combinations for the individual possible MAC frame types. For example, the situation where both
addresses are omitted (source addressing mode = 0 and destination addressing mode = 0) is
only allowed for acknowledgment frames. The address filter in the AT86RF231 has been
designed to apply to IEEE 802.15.4 compliant frames. It can be configured to handle other frame
formats and exceptions.
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8.1.2.6
Auxiliary Security Header Field
The Auxiliary Security Header specifies information required for security processing and has a
variable length. This field determines how the frame is actually protected (security level) and
which keying material from the MAC security PIB is used (see IEEE 802.15.4-2006, section
7.6.1). This field shall be present only if the Security Enabled subfield b3, see Section 8.1.2.3
“Frame Compatibility between IEEE 802.15.4-2003 and IEEE 802.15.4-2006” on page 83, is set
to one. For details of its structure, see IEEE 802.15.4-2006, section 7.6.2. Auxiliary security
header.
8.1.2.7
MAC Service Data Unit (MSDU)
This is the actual MAC payload. It is usually structured according to the individual frame type. A
description can be found in IEEE 802.15.4-2006, section 5.5.3.2.
8.1.2.8
MAC Footer (MFR) Fields
The MAC footer consists of a two-octet Frame Checksum (FCS), for details refer to Section 8.2
“Frame Check Sequence (FCS)” on page 85.
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8.2
Frame Check Sequence (FCS)
The Frame Check Sequence (FCS) is characterized by:
• Indicate bit errors, based on a cyclic redundancy check (CRC) of length 16 bit
• Uses International Telecommunication Union (ITU) CRC polynomial
• Automatically evaluated during reception
• Can be automatically generated during transmission
8.2.1
Overview
The FCS is intended for use at the MAC layer to detect corrupted frames at a first level of filtering. It is computed by applying an ITU CRC polynomial to all transferred bytes following the
length field (MHR and MSDU fields). The frame check sequence has a length of 16 bit and is
located in the last two bytes of a frame (MAC footer, see Figure 8-2 on page 80).
The AT86RF231 applies an FCS check on each received frame. The FCS check result is stored
in register bit RX_CRC_VALID in register 0x06 (PHY_RSSI).
On transmit the radio transceiver generates and appends the FCS bytes during the frame transmission. This behavior can be disabled by setting register bit TX_AUTO_CRC_ON = 0 (register
0x04, TRX_CTRL_1).
8.2.2
CRC Calculation
The CRC polynomial used in IEEE 802.15.4 networks is defined by:
G 16 ( x ) = x
16
+x
12
5
+x +1
The FCS shall be calculated for transmission using the following algorithm:
Let
M ( x ) = b0 x
k–1
+ b1 x
k–2
+ b2 x
k–3
+ … + bk – 2 x + bk – 1
be the polynomial representing the sequence of bits for which the checksum is to be computed.
Multiply M(x) by x16, giving the polynomial
N(x) = M( x) • x
16
Divide N(x) modulo 2 by the generator polynomial, G16(x), to obtain the remainder polynomial,
R ( x ) = r0 x
15
+ r1 x
14
+ … + r 14 x + r 15
The FCS field is given by the coefficients of the remainder polynomial, R(x).
Example:
Considering a 5 octet ACK frame. The MHR field consists of
0100 0000 0000 0000 0101 0110.
The leftmost bit (b0) is transmitted first in time. The FCS is in this case
0010 0111 1001 1110.
The leftmost bit (r0) is transmitted first in time.
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8.2.3
Automatic FCS generation
The automatic FCS generation is performed with register bit TX_AUTO_CRC_ON = 1 (reset
value). This allows the AT86RF231 to compute the FCS autonomously. For a frame with a frame
length specified as N (3 ≤ N ≤ 127), the FCS is calculated on the first N-2 octets in the Frame
Buffer, and the resulting FCS field is transmitted in place of the last two octets from the Frame
Buffer.
If the radio transceivers automatic FCS generation is enabled, the Frame Buffer write access
can be stopped right after MAC payload. There is no need to write FCS dummy bytes.
In RX_AACK mode, when a received frame needs to be acknowledged, the FCS of the ACK
frame is always automatically generated by the AT86RF231, independent of the
TX_AUTO_CRC_ON setting.
Example:
A frame transmission of length five with TX_AUTO_CRC_ON set, is started with a Frame Buffer
write access of five bytes (the last two bytes can be omitted). The first three bytes are used for
FCS generation; the last two bytes are replaced by the internally calculated FCS.
8.2.4
Automatic FCS check
An automatic FCS check is applied on each received frame with a frame length N 2. Register
bit RX_CRC_VALID (register 0x06, PHY_RSSI) is set if the FCS of a received frame is valid.
The register bit is updated when issuing interrupt IRQ_3 (TRX_END) and remains valid until the
next TRX_END interrupt caused by a new frame reception.
In RX_AACK mode, if FCS of the received frame is not valid, the radio transceiver rejects the
frame and the TRX_END interrupt is not issued.
In TX_ARET mode, the FCS and the sequence number of an ACK is automatically checked. If
one of these is not correct, the ACK is not accepted.
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8.2.5
Register Description
Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
+0x04
3
2
1
0
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
0
0
0
SPI_CMD_MODE
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
Refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
Register bit TX_AUTO_CRC_ON controls the automatic FCS generation for TX operations. The
automatic FCS algorithm is performed autonomously by the radio transceiver if register bit
TX_AUTO_CRC_ON = 1.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
Register 0x06 (PHY_RSSI):
The PHY_RSSI register is a multi purpose register that indicates FCS validity, provides random
numbers and shows the actual RSSI value.
Bit
+0x06
7
RX_CRC_VALID
6
5
4
3
RND_VALUE
2
1
0
RSSI
PHY_RSSI
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
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• Bit 7 - RX_CRC_VALID
Reading this register bit indicates whether the last received frame has a valid FCS or not. The
register bit is updated when issuing interrupt IRQ_3 (TRX_END) and remains valid until the next
TRX_END interrupt is issued, caused by a new frame reception.
Table 8-6.
RX Frame FCS Check
Register Bit
RX_CRC_VALID
Value
State Description
0
FCS is not valid
1
FCS is valid
• Bit [6:5] - RND_VALUE
Refer to register description in Section 11.2.2 “Register Description” on page 136.
• Bit [4:0] - RSSI
Refer to register description in Section 8.3.4 “Register Description” on page 90.
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8.3
Received Signal Strength Indicator (RSSI)
The Received Signal Strength Indicator is characterized by:
• Minimum RSSI level is -91 dBm (RSSI_BASE_VAL)
• Dynamic range is 81 dB
• Minimum RSSI value is 0
• Maximum RSSI value is 28
8.3.1
Overview
The RSSI is a 5-bit value indicating the receive power in the selected channel, in steps of 3 dB.
No attempt is made to distinguish IEEE 802.15.4 signals from others, only the received signal
strength is evaluated. The RSSI provides the basis for an ED measurement, see Section 8.4
“Energy Detection (ED)” on page 91.
8.3.2
Reading RSSI
In Basic Operating Mode the RSSI value is valid in any receive state, and is updated every
tTR25 = 2 µs to register 0x06 (PHY_RSSI).
It is not recommended to read the RSSI value when using the Extended Operating Mode. The
automatically generated ED value should be used alternatively, see Section 8.4 “Energy Detection (ED)” on page 91.
8.3.3
Data Interpretation
The RSSI value is a 5-bit value indicating the receive power, in steps of 3 dB and with a range of
0 - 28.
An RSSI value of 0 indicates a receiver RF input power of PRF < -91 dBm. For an RSSI value in
the range of 1 to 28, the RF input power can be calculated as follows:
PRF = RSSI_BASE_VAL + 3*(RSSI -1) [dBm]
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Figure 8-4.
Mapping between RSSI Value and Received Input Power
10
Receiver Input Power PRF [dBm]
0
Measured
-10
Ideal
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
RSSI
8.3.4
Register Description
Register 0x06 (PHY_RSSI):
Bit
+0x06
7
RX_CRC_VALID
6
5
4
3
RND_VALUE
2
1
0
RSSI
PHY_RSSI
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - RX_CRC_VALID
Refer to register description in Section 8.2.5 “Register Description” on page 87.
• Bit [6:5] - RND_VALUE
Refer to register description in section Section 11.2.2 “Register Description” on page 136.
• Bit [4:0] - RSSI
The result of the automated RSSI measurement is stored in register bits RSSI. The value is
updated every 2 µs in receive states.
The read value is a number between 0 and 28 indicating the received signal strength as a linear
curve on a logarithmic input power scale (dBm) with a resolution of 3 dB. An RSSI value of 0
indicates an RF input power of PRF < -91 dBm (see parameter 12.7.16), a value of 28 a power of
PRF 10 dBm (see parameter 12.7.18).
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8.4
Energy Detection (ED)
The Energy Detection (ED) module is characterized by:
• 85 unique energy levels defined
• 1 dB resolution
8.4.1
Overview
The receiver ED measurement is used by the network layer as part of a channel selection algorithm. It is an estimation of the received signal power within the bandwidth of an IEEE 802.15.4
channel. No attempt is made to identify or decode signals on the channel. The ED value is calculated by averaging RSSI values over eight symbols (128 µs).
For High Data Rate Modes the automated ED measurement duration is reduced to 32 µs, refer
to Section 11.3 “High Data Rate Modes” on page 137. For manually initiated ED measurements
in these modes the measurement period is still 128 µs as long as the receiver is in RX_ON state.
8.4.2
Measurement Description
There are two ways to initiate an ED measurement:
• Manually, by writing an arbitrary value to register 0x07 (PHY_ED_LEVEL), or
• Automatically, after detection of a valid SHR of an incoming frame.
For manually initiated ED measurements the radio transceiver needs to be in one of the states
RX_ON or BUSY_RX state. The end of the ED measurement is indicated by an interrupt
IRQ_4 (CCA_ED_DONE).
An automated ED measurement is started if an SHR is detected. The end of the automated
measurement is not signaled by an interrupt.
The measurement result is stored after tTR26 = 140 µs (128 µs measurement duration and processing delay) in register 0x07 (PHY_ED_LEVEL).
Thus by using Basic Operating Mode, a valid ED value from the currently received frame is
accessible 108 µs after IRQ_2 (RX_START) and remains valid until a new RX_START interrupt
is generated by the next incoming frame or until another ED measurement is initiated.
By using the Extended Operating Mode, it is recommended to mask IRQ_2 (RX_START), thus
the interrupt cannot be used as timing reference. A successful frame reception is signalized by
interrupt IRQ_3 (TRX_END). The minimum time span between a TRX_END interrupt and a following SFD detection is t TR27 = 96 µs due to the length of the SHR. Including the ED
measurement time, the ED value needs to be read within 224 µs after the TRX_END interrupt;
otherwise, it could be overwritten by the result of the next measurement cycle. This is important
for time critical applications or if interrupt IRQ_2 (RX_START) is not used to indicate the reception of a frame.
Note, it is not recommended to manually initiate an ED measurement when using the Extended
Operating Mode.
The values of the register 0x07 (PHY_ED_LEVEL) are:
Table 8-7.
Register Bit PHY_ED_LEVEL Interpretation
PHY_ED_LEVEL
Description
0xFF
Reset value
0x00.... 0x54
ED measurement result of the last ED measurement
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8.4.3
Data Interpretation
The PHY_ED_LEVEL is an 8-bit register. The ED value of the AT86RF231 has a valid range
from 0x00 to 0x54 with a resolution of 1 dB. All other values do not occur; a value of 0xFF indicates the reset value. A value of PHY_ED_LEVEL = 0 indicates that the measured energy is
less than -91 dBm (see parameter 12.7.16 RSSI_BASE_VAL, Section 12.7 “Receiver Characteristics” on page 160). Due to environmental conditions (temperature, voltage, semiconductor
parameters, etc.) the calculated ED value has a maximum tolerance of ±5 dB, this is to be considered as constant offset over the measurement range.
An ED value of 0 indicates an RF input power of PRF ≤ -91 dBm. For an ED value in the range of
0 to 84, the RF input power can be calculated as follows:
PRF = -91 + ED [dBm]
Figure 8-5.
Mapping between Received Input Power and ED Value
10
Receiver Input Power PRF [dBm]
0
Measured
-10
Ideal
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
10
20
30
40
50
60
70
80
90
PHY_ED_LEVEL (register 0x07)
8.4.4
Interrupt Handling
Interrupt IRQ_4 (CCA_ED_DONE) is issued at the end of a manually initiated ED measurement.
Note that an ED request should only be initiated in receive states. Otherwise the radio transceiver generates an IRQ_4 (CCA_ED_DONE); however no ED measurement was performed.
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8.4.5
Register Description
Register 0x07 (PHY_ED_LEVEL):
The PHY_ED_LEVEL register contains the result of an ED measurement.
Bit
7
6
5
+0x07
4
3
2
1
0
ED_LEVEL[7:0]
PHY_ED_LEVEL
Read/Write
R
R
R
R
R
R
R
R
Reset Value
1
1
1
1
1
1
1
1
• Bit [7:0] - ED_LEVEL
The minimum ED value (ED_LEVEL = 0) indicates receiver power less than or equal to
RSSI_BASE_VAL. The range is 84 dB with a resolution of 1 dB and an absolute accuracy of
±5 dB. A manual ED measurement can be initiated by a write access to the register. A value
0xFF signals that a measurement has never been started yet (reset value).
The measurement duration is 8 symbol periods (128 µs) for a data rate of 250 kb/s.
For High Data Rate Modes the automated measurement duration is reduced to 32 µs, refer to
Section 11.3 “High Data Rate Modes” on page 137. For manually initiated ED measurements in
these modes the measurement period is still 128 µs as long as the receiver is in RX_ON state.
A value other than 0xFF indicates the result of the last ED measurement.
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8.5
Clear Channel Assessment (CCA)
The main features of the Clear Channel Assessment (CCA) module are:
• All 4 modes are available as defined by IEEE 802.15.4-2006 in section 6.9.9
• Adjustable threshold for energy detection algorithm
8.5.1
Overview
A CCA measurement is used to detect a clear channel. Four modes are specified by
IEEE 802.15.4 - 2006:
Table 8-8.
CCA Mode
CCA Mode Overview
Description
1
Energy above threshold.
CCA shall report a busy medium upon detecting any energy above the ED threshold.
2
Carrier sense only.
CCA shall report a busy medium only upon the detection of a signal with the modulation
and spreading characteristics of an IEEE 802.15.4 compliant signal. The signal strength
may be above or below the ED threshold.
0, 3
Carrier sense with energy above threshold.
CCA shall report a busy medium using a logical combination of
– Detection of a signal with the modulation and spreading
characteristics of this standard and
– Energy above the ED threshold.
Where the logical operator may be configured as either OR (mode 0) or AND (mode 3).
8.5.2
Configuration and Request
The CCA modes are configurable via register 0x08 (PHY_CC_CCA).
Using the Basic Operating Mode, a CCA request can be initiated manually by setting
CCA_REQUEST = 1 (register 0x08, PHY_CC_CCA), if the AT86RF231 is in any RX state. The
current channel status (CCA_STATUS) and the CCA completion status (CCA_DONE) are
accessible in register 0x01 (TRX_STATUS).
The CCA evaluation is done over eight symbol periods and the result is accessible
tTR28 = 140 µs (128 µs measurement duration and processing delay) after the request. The end
of a manually initiated CCA measurement is indicated by an interrupt IRQ_4 (CCA_ED_DONE).
The sub-register CCA_ED_THRES of register 0x09 (CCA_THRES) defines the received power
threshold of the "Energy above threshold" algorithm. The threshold is calculated by
RSSI_BASE_VAL + 2 * CCA_ED_THRES [dBm]. Any received power above this level is interpreted as a busy channel.
Note, it is not recommended to manually initiate a CCA measurement when using the Extended
Operating Mode.
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8.5.3
Data Interpretation
The current channel status (CCA_STATUS) and the CCA completion status (CCA_DONE) are
accessible in register 0x01 (TRX_STATUS). Note, register bits CCA_DONE and CCA_STATUS
are cleared in response to a CCA_REQUEST.
The completion of a measurement cycle is indicated by CCA_DONE = 1. If the radio transceiver
detected no signal (idle channel) during the measurement cycle, the CCA_STATUS bit is set to
1.
When using the "ene rg y above th re shold" algorith m, any received power abov e
CCA_ED_THRES level is interpreted as a busy channel. The "carrier sense" algorithm reports a
busy channel when detecting an IEEE 802.15.4 signal above the RSSI_BASE_VAL (see parameter 12.7.16). The radio transceiver is also able to detect signals below this value, but the
detection probability decreases with the signal power. It is almost zero at the radio transceivers
sensitivity level (see parameter 12.7.1).
8.5.4
Interrupt Handling
Interrupt IRQ_4 (CCA_ED_DONE) is issued at the end of a manually initiated CCA
measurement.
Notes
• A CCA request should only be initiated in Basic Operating Mode receive states. Otherwise
the radio transceiver generates an IRQ_4 (CCA_ED_DONE) and sets the register bit
CCA_DONE = 1, even though no CCA measurement was performed.
• Requesting a CCA measurement in BUSY_RX state and during an ED measurement, an
IRQ_4 (CCA_ED_DONE) could be issued immediately after the request. If in this case
register bit CCA_DONE = 0, an additional interrupt CCA_ED_DONE is issued after finishing
the CCA measurement and register bit CCA_DONE is set to 1.
8.5.5
Measurement Time
The response time for a manually initiated CCA measurement depends on the receiver state.
In RX_ON state the CCA measurement is done over eight symbol periods and the result is
accessible 140 µs after the request (see above).
In BUSY_RX state the CCA measurement duration depends on the CCA Mode and the CCA
request relative to the reception of an SHR. The end of the CCA measurement is indicated by an
IRQ_4 (CCA_ED_DONE). The variation of a CCA measurement period in BUSY_RX state is
described in Table 8-9 on page 95.
Table 8-9.
CCA Mode
1
CCA Measurement Period and Access in BUSY_RX state
Request within ED measurement(1)
Energy above threshold.
CCA result is available after finishing
automated ED measurement period.
2
Request after ED measurement
CCA result is immediately available after
request.
Carrier sense only.
CCA result is immediately available after request.
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Table 8-9.
3
CCA Measurement Period and Access in BUSY_RX state
Carrier sense with Energy above threshold (AND).
CCA result is available after finishing
automated ED measurement period.
0
Carrier sense with Energy above threshold (OR).
CCA result is available after finishing
automated ED measurement period
Note:
CCA result is immediately available after
request.
CCA result is immediately available after
request.
1. After receiving the SHR an automated ED measurement is started with a length of 8 symbol
periods (PSDU rate 250 kb/s), refer to Section 8.4 “Energy Detection (ED)” on page 91. This
automated ED measurement must be finished to provide a result for the CCA measurement.
Only one automated ED measurement per frame is performed.
It is recommended to perform CCA measurements in RX_ON state only. To avoid switching
accidentally to BUSY_RX state the SHR detection can be disabled by setting register bit
RX_PDT_DIS (register 0x15, RX_SYN), refer to Section 9.1 “Receiver (RX)” on page 101. The
receiver remains in RX_ON state to perform a CCA measurement until the register bit
RX_PDT_DIS is set back to continue the frame reception. In this case the CCA measurement
duration is 8 symbol periods.
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8.5.6
Register Description
Register 0x01 (TRX_STATUS):
Two register bits of register 0x01 (TRX_STATUS) signal the status of the CCA measurement.
Bit
7
6
5
CCA_DONE
CCA_STATUS
Reserved
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
+0x01
4
3
2
1
0
TRX_STATUS
TRX_STATUS
• Bit 7 - CCA_DONE
This register indicates if a CCA request is completed. This is also indicated by an interrupt
IRQ_4 (CCA_ED_DONE). Note, register bit CCA_DONE is cleared in response to a
CCA_REQUEST.
Table 8-10.
CCA Algorithm Status
Register Bit
Value
State Description
CCA_DONE
0
CCA calculation not finished
1
CCA calculation finished
• Bit 6 - CCA_STATUS
After a CCA request is completed the result of the CCA measurement is available in register bit
CCA_STATUS. Note, register bit CCA_STATUS is cleared in response to a CCA_REQUEST.
Table 8-11.
CCA Status Result
Register Bit
Value
CCA_STATUS
State Description
0
Channel indicated as busy
1
Channel indicated as idle
• Bit 5 - Reserved
• Bit [4:0] - TRX_STATUS
Refer to Section 7.1.5 “Register Description” on page 44 and Section 7.2.7 “Register Description - Control Registers” on page 68.
Register 0x08 (PHY_CC_CCA):
This register is provided to initiate and control a CCA measurement.
Bit
+0x08
7
6
CCA_REQUEST
5
4
3
CCA_MODE
2
1
0
CHANNEL
PHY_CC_CCA
Read/Write
W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
1
0
1
1
• Bit 7 - CCA_REQUEST
A manual CCA measurement is initiated with setting CCA_REQUEST = 1. The end of the CCA
measurement is indicated by interrupt IRQ_4 (CCA_ED_DONE). Register bits CCA_DONE and
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CCA_STATUS (register 0x01, TRX_STATUS) are updated after a CCA_REQUEST. The register bit is automatically cleared after requesting a CCA measurement with CCA_REQUEST = 1.
• Bit [6:5] - CCA_MODE
The CCA mode can be selected using register bits CCA_MODE.
Table 8-12.
CCA Status Result
Register Bit
Value
State Description
CCA_MODE
0
Mode 3a, Carrier sense OR energy above threshold
1
Mode 1, Energy above threshold
2
Mode 2, Carrier sense only
3
Mode 3b, Carrier sense AND energy above threshold
Note that IEEE 802.15.4-2006 CCA Mode 3 defines the logical combination of CCA Mode 1 and
2 with the logical operators AND or OR. This can be selected with:
• CCA_MODE = 0
for logical operation OR, and
• CCA_MODE = 3
for logical operation AND.
• Bit [4:0] - CHANNEL
Refer to Section 9.7 “Frequency Synthesizer (PLL)” on page 121.
Register 0x09 (CCA_THRES):
This register sets the ED threshold level for CCA.
Bit
7
6
+0x09
5
4
3
2
Reserved
1
0
CCA_ED_THRES
CCA_THRES
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
1
0
0
0
1
1
1
• Bit [7:5] - Reserved
• Bit [4:0] - CCA_ED_THRES
The CCA Mode 1 request indicates a busy channel if the measured received power is above
RSSI_BASE_VAL + 2 * CCA_ED_THRES [dBm]. CCA Modes 0 and 3 are logical related to this
result.
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8.6
Link Quality Indication (LQI)
According to IEEE 802.15.4, the LQI measurement is a characterization of the strength and/or
quality of a received packet. The measurement may be implemented using receiver ED, a signal-to-noise ratio estimation, or a combination of these methods. The use of the LQI result by the
network or application layers is not specified in this standard. LQI values shall be an integer
ranging from 0x00 to 0xFF. The minimum and maximum LQI values (0x00 and 0xFF) should be
associated with the lowest and highest quality compliant signals, respectively, and LQI values in
between should be uniformly distributed between these two limits.
8.6.1
Overview
The LQI measurement of the AT86RF231 is implemented as a measure of the link quality which
can be described with the packet error rate (PER) for this link. An LQI value can be associated
with an expected packet error rate. The PER is the ratio of erroneous received frames to the
total number of received frames. A PER of zero indicates no frame error, whereas at a PER of
one no frame was received correctly.
The radio transceiver uses correlation results of multiple symbols within a frame to determine
the LQI value. This is done for each received frame. The minimum frame length for a valid LQI
value is two octets PSDU. LQI values are integers ranging from 0 to 255.
As an example, Figure 8-6 on page 99 shows the conditional packet error when receiving a certain LQI value.
Figure 8-6.
Conditional Packet Error Rate versus LQI
1
0.9
0.8
0.7
PER
0.6
0.5
0.4
0.3
0.2
0.1
0
0
50
100
150
200
250
LQI
The values are taken from received frames of PSDU length of 20 octets on transmission channels with reasonable low multipath delay spreads. If the transmission channel characteristic has
higher multipath delay spread than assumed in the example, the PER is slightly higher for a cer99
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tain LQI value. Since the packet error rate is a statistical value, the PER shown in Section 8-6
“Conditional Packet Error Rate versus LQI” on page 99 is based on a huge number of transactions. A reliable estimation of the packet error rate cannot be based on a single or a small
number of LQI values.
8.6.2
Request an LQI Measurement
The LQI byte can be obtained after a frame has been received by the radio transceiver. One
additional byte is automatically attached to the received frame containing the LQI value. This
information can also be read via Frame Buffer read access, see Section 6.2.2 “Frame Buffer
Access Mode” on page 20. The LQI byte can be read after IRQ_3 (TRX_END) interrupt.
8.6.3
Data Interpretation
According to IEEE 802.15.4 a low LQI value is associated with low signal strength and/or high
signal distortions. Signal distortions are mainly caused by interference signals and/or multipath
propagation. High LQI values indicate a sufficient high signal power and low signal distortions.
Note, the received signal power as indicated by received signal strength indication (RSSI) value
or energy detection (ED) value of the AT86RF231 do not characterize the signal quality and the
ability to decode a signal.
As an example, a received signal with an input power of about 6 dB above the receiver sensitivity likely results in a LQI value close to 255 for radio channels with very low signal distortions.
For higher signal power the LQI value becomes independent of the actual signal strength. This
is because the packet error rate for these scenarios tends towards zero and further increased
signal strength, i.e. increasing the transmission power does not decrease the error rate any further. In this case RSSI or ED can be used to evaluate the signal strength and the link margin.
ZigBee networks often require the identification of the "best" routing between two nodes. Both,
the LQI and the RSSI/ED can be used for this, dependent on the optimization criteria. If a low
packet error rate (corresponding to high throughput) is the optimization criteria then the LQI
value should be taken into consideration. If a low transmission power or the link margin is the
optimization criteria then the RSSI/ED value is also helpful.
Combinations of LQI, RSSI and ED are possible for routing decisions. As a rule of thumb RSSI
and ED values are useful to differentiate between links with high LQI values. Transmission links
with low LQI values should be discarded for routing decisions even if the RSSI/ED values are
high. This is because RSSI/ED does not say anything about the possibility to decode a signal. It
is only an information about the received signal strength whereas the source can be an
interferer.
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9. Module Description
9.1
9.1.1
Receiver (RX)
Overview
The AT86RF231 receiver is split into an analog radio front end and a digital base band processor (RX BBP), see Figure 9-1 on page 101.
Figure 9-1.
Receiver Block Diagram
Analog Domain
LO
Digital Domain
Frame
Buffer
RFP
LNA
PPF
BPF
Limiter
ADC
RX BBP
SPI
SPI
I/F
RFN
AGC
RSSI
Control, Registers
µC
I/F
The differential RF signal is amplified by a low noise amplifier (LNA), filtered (PPF) and down
converted to an intermediate frequency by a mixer. Channel selectivity is performed using an
integrated band pass filter (BPF). A limiting amplifier (Limiter) provides sufficient gain to overcome the DC offset of the succeeding analog-to-digital converter (ADC) and generates a digital
RSSI signal. The ADC output signal is sampled and processed further by the digital base band
receiver (RX BBP).
The RX BBP performs additional signal filtering and signal synchronization. The frequency offset
of each frame is calculated by the synchronization unit and is used during the remaining receive
process to correct the offset. The receiver is designed to handle frequency and symbol rate deviations up to ±120 ppm, caused by combined receiver and transmitter deviations. For details
refer to Section 12.5 “General RF Specifications” on page 158 parameter 12.5.8. Finally the signal is demodulated and the data are stored in the Frame Buffer.
In Basic Operating Mode, refer to Section 7.1 “Basic Operating Mode” on page 33, the reception
of a frame is indicated by an interrupt IRQ_2 (RX_START). Accordingly its end is signalized by
an interrupt IRQ_3 (TRX_END). Based on the quality of the received signal a link quality indicator (LQI) is calculated and appended to the frame, refer to Section 8.6 “Link Quality Indication
(LQI)” on page 99. Additional signal processing is applied to the frame data to provide further
status information like ED value (register 0x07, ED_LEVEL) and FCS correctness (register
0x06, PHY_RSSI).
Beyond these features the Extended Operating Mode of the AT86RF231 supports address filtering and pending data indication. For details refer to Section 7.2 “Extended Operating Mode” on
page 47.
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9.1.2
Frame Receive Procedure
The frame receive procedure including the radio transceiver setup for reception and reading
PSDU data from the Frame Buffer is described in Section 10.1 “Frame Receive Procedure” on
page 126.
9.1.3
Configuration
In Basic Operating Mode the receiver is enabled by writing command RX_ON to register bits
TRX_CMD (register 0x02, TRX_STATE) in states TRX_OFF or PLL_ON. Similarly in Extended
Operating Mode, the receiver is enabled for RX_AACK operation from states TRX_OFF or
PLL_ON by writing the command RX_AACK_ON. There is no additional configuration required
to receive IEEE 802.15.4 compliant frames when using the Basic Operating Mode. However, the
frame reception in the Extended Operating Mode requires further register configurations, for
details refer to Section 7.2 “Extended Operating Mode” on page 47.
The AT86RF231 receiver has an outstanding sensitivity performance of -101 dBm. At certain
environmental conditions or for High Data Rate Modes, refer to Section 11.3 “High Data Rate
Modes” on page 137, it may be useful to manually decrease this sensitivity. This is achieved by
adjusting the synchronization header detector threshold using register bits RX_PDT_LEVEL
(register 0x15, RX_SYN). Received signals with an RSSI value below the threshold do not activate the demodulation process.
Furthermore, it may be useful to protect a received frame against overwriting by subsequent
received frames.
A Dynamic Frame Buffer Protection is enabled with register bit RX_SAFE_MODE (register
0x0C, TRX_CTRL_2) set, see Section 11.8 “Dynamic Frame Buffer Protection” on page 154.
The receiver remains in RX_ON or RX_AACK_ON state until the whole frame is read by the
microcontroller, indicated by /SEL = H during the SPI Frame Receive Mode. The Frame Buffer
content is only protected if the FCS is valid.
A Static Frame Buffer Protection is enabled with register bit RX_PDT_DIS (register 0x15,
RX_SYN) set. The receiver remains in RX_ON or RX_AACK_ON state and no further SHR is
detected until the register bit RX_PDT_DIS is set back.
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9.1.4
Register Description
Register 0x15 (RX_SYN):
This register controls the sensitivity threshold of the receiver.
Bit
+0x15
7
6
5
RX_PDT_DIS
4
3
2
Reserved
1
0
RX_PDT_LEVEL
RX_SYN
Read/Write
R/W
R
R
R
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - RX_PDT_DIS
RX_PDT_DIS = 1 prevents the reception of a frame even if the radio transceiver is in receive
modes. An ongoing frame reception is not affected. This operation mode is independent of the
setting of register bits RX_PDT_LEVEL.
• Bit [6:4] - Reserved
• Bit [3:0] - RX_ PDT_LEVEL
These register bits desensitize the receiver such that frames with an RSSI level below the
RX_PDT_LEVEL threshold level (if RX_PDT_LEVEL > 0) are not received. The threshold level
can be calculated according to the following formula:
RX_THRES = RSSI_BASE_VAL + 3 * (RX_PDT_LEVEL -1), for RX_PDT_LEVEL > 0
Examples for certain register settings are given in Table 9-1 on page 103
Table 9-1.
Receiver Desensitization Threshold Level - RX_PDT_LEVEL
Value [Register]
RX Input Threshold Level
Value [dBm]
0x0
≤ RSSI_BASE_VAL (reset value)
RSSI value not considered
0x1
> RSSI_BASE_VAL + 0 * 3
> -90
0xE
> RSSI_BASE_VAL + 13 * 3
> -51
0xF
> RSSI_BASE_VAL + 14 * 3
> -48
...
If register bits RX_PDT_LEVEL > 0 the current consumption of the receiver in states RX_ON
and RX_AACK_ON is reduced by 500 µA, refer to Section 12.8 “Current Consumption Specifications” on page 161 parameter 12.8.4.
If register bits RX_PDT_LEVEL = 0 (reset value) all frames with a valid SHR and PHR are
received, independently of their signal strength.
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9.2
9.2.1
Transmitter (TX)
Overview
The AT86RF231 transmitter consists of a digital base band processor (TX BBP) and an analog
radio front end, see Figure 9-2 on page 104.
Figure 9-2.
Transmitter Block Diagram
Ext. RF front-end and
Output Power Control
DIG3/4
RFP
PA
Buf
PLL – TX Modulation
µC
I/F
Control, Registers
TX Data
TX BBP
SPI
SPI
I/F
RFN
Frame
Buffer
Analog Domain
Digital Domain
The TX BBP reads the frame data from the Frame Buffer and performs the bit-to-symbol and
symbol-to-chip mapping as specified by IEEE 802.15.4 in section 6.5.2. The O-QPSK modulation signal is generated and fed into the analog radio front end.
The fractional-N frequency synthesizer (PLL) converts the baseband transmit signal to the RF
signal, which is amplified by the power amplifier (PA). The PA output is internally connected to
bidirectional differential antenna pins (RFP, RFN), so that no external antenna switch is needed.
9.2.2
Frame Transmit Procedure
The frame transmit procedure including writing PSDU data in the Frame Buffer and initiating a
transmission is described in Section 10.2 “Frame Transmit Procedure” on page 127, Frame
Transmit Procedure.
9.2.3
Configuration
The maximum output power of the transmitter is typically +3 dBm. The output power can be configured via register bits TX_PWR (register 0x05, PHY_TX_PWR). The output power of the
transmitter can be controlled over a range of 20 dB.
A transmission can be started from PLL_ON or TX_ARET_ON state by a rising edge of pin
SLP_TR or by writing TX_START command to register bits TRX_CMD (register 0x02,
TRX_STATE).
9.2.4
TX Power Ramping
To optimize the output power spectral density (PSD), the PA buffer and PA are enabled sequentially. This is illustrated by a timing example using default settings, shown in Figure 9-3 on page
105. In this example the transmission is initiated with the rising edge of pin 11 (SLP_TR). The
radio transceiver state changes from PLL_ON to BUSY_TX. The modulation starts 16 µs after
SLP_TR.
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Figure 9-3.
TX Power Ramping
0
TRX_STATE
4
2
6
8
10
PLL_ON
12
14
16
18
Length [µs]
BUSY_TX
SLP_TR
PA buffer
PA_BUF_LT
PA
PA_LT
Modulation
1 1 0 1 1 0 0 1 1
When using an external RF front-end (refer to Section 11.5 “RX/TX Indicator” on page 147) it
may be required to adjust the startup time of the external PA relative to the internal building
blocks to optimize the overall PSD. This can be achieved using register bits PA_BUF_LT and
PA_LT.
9.2.5
Register Description
Register 0x05 (PHY_TX_PWR):
This register controls the output power and the ramping of the transmitter.
Bit
7
+0x05
6
5
4
PA_BUF_LT
3
2
PA_LT
1
0
TX_PWR
PHY_TX_PWR
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
1
0
0
0
0
0
0
• Bit [7:6] - PA_BUF_LT
These register bits control the enable lead time of the internal PA buffer relative to the enable
time of the internal PA. This time is further used to derive a control signal for an external RF
front-end to switch between receive and transmit, for details refer to Section 11.5.
Table 9-2.
PA Buffer Enable Time Relative to the PA
Register Bits
Value
PA Buffer Lead Time [µs]
PA_BUF_LT
0
0
1
2
2
4
3
6
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• Bit [5:4] - PA_LT
These register bits control the enable lead time of the internal PA relative to the beginning of the
transmitted frame.
Table 9-3.
Register Bits
PA_LT
PA Enable Time Relative to the Start of the Frame (SHR)
Value
PA Lead Time [µs]
0
2
1
4
2
6
3
8
• Bit [3:0] - TX_PWR
These register bits determine the TX output power of the AT86RF231.
Table 9-4.
Register Bits
TX_PWR
AT86RF231 TX Output Power Setting
Value
TX Output Power [dBm]
0x0
3.0
0x1
2.8
0x2
2.3
0x3
1.8
0x4
1.3
0x5
0.7
0x6
0.0
0x7
-1
0x8
-2
0x9
-3
0xA
-4
0xB
-5
0xC
-7
0xD
-9
0xE
-12
0xF
-17
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9.3
Frame Buffer
The AT86RF231 contains a 128 byte dual port SRAM. One port is connected to the SPI interface, the other to the internal transmitter and receiver modules. For data communication, both
ports are independent and simultaneously accessible.
The Frame Buffer uses the address space 0x00 to 0x7F for RX and TX operation of the radio
transceiver and can keep one IEEE 802.15.4 RX or one TX frame of maximum length at a time.
Frame Buffer access modes are described in Section 6.6.2 “Register Description” on page 30.
Frame Buffer access conflicts are indicated by an under run interrupt IRQ_6 (TRX_UR). Note
that this interrupt also occurs on the attempt to write frames longer than 127 octets to the Frame
Buffer. In that case the content of the Frame Buffer cannot be guaranteed.
Frame Buffer access is only possible if the digital voltage regulator is turned on. This is valid in
all device states except in SLEEP state. An access in P_ON state is possible if pin 17 (CLKM)
provides the 1 MHz master clock.
9.3.1
Data Management
Data in Frame Buffer (received data or data to be transmitted) remains valid as long as:
• No new frame or other data are written into the buffer over SPI
• No new frame is received (in any BUSY_RX state)
• No state change into SLEEP state is made
• No RESET took place
By default there is no protection of the Frame Buffer against overwriting. Therefore, if a frame is
received during Frame Buffer read access of a previously received frame, interrupt IRQ_6
(TRX_UR) is issued and the stored data might be overwritten.
Even so, the old frame data can be read, if the SPI data rate is higher than the effective over air
data rate. For a data rate of 250 kb/s a minimum SPI clock rate of 1 MHz is recommended.
Finally the microcontroller should check the transferred frame data integrity by an FCS check.
To protect the Frame Buffer content against being overwritten by newly incoming frames the
radio transceiver state should be changed to PLL_ON state after reception. This can be
achieved by writing immediately the command PLL_ON to register bits TRX_CMD (register
0x02, TRX_STATE) after receiving the frame, indicated by IRQ_3 (TRX_END).
Alternatively Dynamic Frame Buffer Protection can be used to protect received frames against
overwriting, for details refer to Section 11.8 “Dynamic Frame Buffer Protection” on page 154.
Both procedures do not protect the Frame Buffer from overwriting by the microcontroller.
In Extended Operating Mode during TX_ARET operation, see Section 7.2.4 “TX_ARET_ON Transmit with Automatic Retry and CSMA-CA Retry” on page 64, the radio transceiver switches
to receive, if an acknowledgement of a previously transmitted frame was requested. During this
period received frames are evaluated, but not stored in the Frame Buffer. This allows the radio
transceiver to wait for an acknowledgement frame and retry the frame transmission without writing them again.
A radio transceiver state change, except a transition to SLEEP state or a reset, does not affect
the Frame Buffer contents. If the radio transceiver is forced into SLEEP, the Frame Buffer is
powered off and the stored data gets lost.
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9.3.2
User accessible Frame Content
The AT86RF231 supports an IEEE 802.15.4 compliant frame format as shown in Figure 9-4 on
page 108.
Figure 9-4.
AT86RF231 Frame Structure
Length [octets]
0
4
5
Preamble Sequence
SFD
Duration
4 octets / 128 µs
1
Access
SHR not accesible
PHY generated
Frame
Notes:
6
PHR(1)
n+3
Payload
n+5
FCS
n octets / n • 32 µs (n <= 128)
n+6
LQI(2)
1
TX: Frame Buffer content
RX: Frame Buffer content
1. Stored into Frame Buffer for TX operation
2. Stored into Frame Buffer during frame reception.
A frame comprises two sections, the radio transceiver internally generated SHR field and the
user accessible part stored in the Frame Buffer. The SHR contains the preamble and the SFD
field. The variable frame section contains the PHR and the PSDU including the FCS, see Section 8.2 “Frame Check Sequence (FCS)” on page 85.
The Frame Buffer content differs depending on the direction of the communication (receive or
transmit). To access the data follow the procedures described in Section 6.2.2 “Frame Buffer
Access Mode” on page 20.
During frame reception, the payload and the link quality indicator (LQI) value of a successfully
received frame are stored in the Frame Buffer. The radio transceiver appends the LQI value to
the frame data after the last received octet. The frame length information is not stored in the
Frame Buffer. When using the Frame Buffer access mode to read the Frame Buffer content, the
frame length information is placed before the payload.
If the SRAM read access is used to read an RX frame, the frame length field (PHR) cannot be
accessed. The SHR (except the SFD used to generate the SHR) can generally not be read by
the microcontroller.
For frame transmission, the PHR and the PSDU needs to be stored in the Frame Buffer. The
PHR byte is the first byte in the Frame Buffer and must be calculated based on the PHR and the
PSDU. The maximum frame size supported by the radio transceiver is 128 bytes. If the
TX_AUTO_CRC_ON bit is set in register 0x05 (PHY_TX_PWR), the FCS field of the PSDU is
replaced by the automatically calculated FCS during frame transmission. That's why there is no
need to write the FCS field when using the automatic FCS generation.
To manipulate individual bytes of the Frame Buffer a SRAM write access can be used instead.
For non IEEE 802.15.4 compliant frames, the minimum frame length supported by the radio
transceiver is one byte (Frame Length Field + 1 byte of data).
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9.3.3
Interrupt Handling
Access conflicts may occur when reading and writing data simultaneously at the two independent ports of the Frame Buffer, TX/RX BBP and SPI. Both of these ports have their own address
counter that points to the Frame Buffer's current address.
Access violations occurs during concurrent Frame Buffer read or write accesses, when the SPI
port's address counter value becomes higher than or equal to that of TX/RX BBP port.
While receiving a frame, primarily the data needs to be stored in the Frame Buffer before reading it. This can be ensured by accessing the Frame Buffer 32 µs after IRQ_2 (RX_START) at the
earliest. When reading the frame data continuously the SPI data rate shall be lower than 250
kb/s to ensure no under run interrupt occurs. To avoid access conflicts and to simplify the Frame
Buffer read access Frame Buffer Empty indication may be used, for details refer to Section 11.7
“Frame Buffer Empty Indicator” on page 152.
While transmitting an access violation occurs during a Frame Buffer write access, when the SPI
port's address counter value becomes less than or equal to that of TX BBP port.
Both these access violations may cause data corruption and are indicated by IRQ_6 (TRX_UR)
interrupt when using the Frame Buffer access mode. Access violations are not indicated when
using the SRAM access mode.
Notes
• Interrupt IRQ_6 (TRX_UR) is valid 64 µs after IRQ_2 (RX_START). The occurrence of the
interrupt can be disregarded when reading the first byte of the Frame Buffer between 32 µs
and 64 µs after the RX_START interrupt.
• If a Frame Buffer read access is not finished until a new frame is received, a TRX_UR
interrupt occurs. Nevertheless the old frame data can be read, if the SPI data rate is higher
than the effective PHY data rate. A minimum SPI clock rate of 1 MHz is recommended in this
case. Finally, the microcontroller should check the integrity of the transferred frame data by
calculating the FCS.
• When writing data to the Frame Buffer during frame transmission, the SPI data rate shall be
higher than the PHY data rate to ensure no under run interrupt. The first byte of the PSDU
data must be available in the Frame Buffer before SFD transmission is complete, which takes
176 µs (16 µs PA ramp up + 160 µs SHR) from the rising edge of SLP_TR pin (see Figure 72 on page 39).
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9.4
Voltage Regulators (AVREG, DVREG)
The main features of the Voltage Regulator blocks are:
• Bandgap stabilized 1.8V supply for analog and digital domain
• Low dropout (LDO) voltage regulator
• Configurable for usage of external voltage regulator
9.4.1
Overview
The internal voltage regulators supply a stabilized voltage to the AT86RF231. The AVREG provides the regulated 1.8V supply voltage for the analog section and the DVREG supplies the 1.8V
supply voltage for the digital section.
A simplified schematic of the internal voltage regulator is shown in Figure 9-5 on page 110.
Figure 9-5.
Simplified Schematic of AVREG/DVREG
(D)EVDD
Bandgap
voltage
reference
1.25V
AVDD,
DVDD
The voltage regulators require bypass capacitors for stable operation. The value of the bypass
capacitors determine the settling time of the voltage regulators. The bypass capacitors shall be
placed as close as possible to the pins and shall be connected to ground with the shortest possible traces.
9.4.2
Configuration
The voltage regulators can be configured by the register 0x10 (VREG_CTRL).
It is recommended to use the internal regulators, but it is also possible to supply the low voltage
domains by an external voltage supply. For this configuration, the internal regulators need to be
switched off by setting the register bits to the values AVREG_EXT = 1 and DVREG_EXT = 1. A
regulated external supply voltage of 1.8V needs to be connected to the pins 13, 14 (DVDD) and
pin 29 (AVDD). When turning on the external supply, ensure a sufficiently long stabilization time
before interacting with the AT86RF231.
9.4.3
Data Interpretation
The status bits AVDD_OK = 1 and DVDD_OK = 1 of register 0x10 (VREG_CTRL) indicate an
enabled and stable internal supply voltage. Reading value 0 indicates a disabled or internal supply voltage not settled to the final value.
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9.4.4
Register Description
Register 0x10 (VREG_CTRL):
This register controls the use of the voltage regulators and indicates the status of these.
7
6
AVREG_EXT
AVDD_OK
Read/Write
R/W
R
R/W
Reset Value
0
0
0
Bit
+0x10
5
4
3
2
DVREG_EXT
DVDD_OK
R/W
R/W
R
R/W
R/W
0
0
0
0
0
Reserved
1
0
Reserved
VREG_CTRL
• Bit 7 - AVREG_EXT
If set this register bit disables the internal analog voltage regulator to apply an external regulated
1.8V supply for the analog building blocks.
Table 9-5.
Regulated Voltage Supply Control for Analog Building Blocks
Register Bit
Value
Description
AVREG_EXT
0
Internal voltage regulator enabled, analog section
1
Internal voltage regulator disabled, use external regulated 1.8V
supply voltage for the analog section
• Bit 6 - AVDD_OK
This register bit indicates if the internal 1.8V regulated voltage supply AVDD has settled. The bit
is set to logic high, if AVREG_EXT = 1.
Table 9-6.
Regulated Voltage Supply Control for Analog Building Blocks
Register Bit
Value
AVDD_OK
Description
0
Analog voltage regulator disabled or supply voltage not stable
1
Analog supply voltage has settled
• Bit [5:4] - Reserved
• Bit 3 - DVREG_EXT
If set this register bit disables the internal digital voltage regulator to apply an external regulated
1.8V supply for the digital building blocks.
Table 9-7.
Regulated Voltage Supply Control for Digital Building Blocks
Register Bit
Value
Description
DVREG_EXT
0
Internal voltage regulator enabled, digital section
1
Internal voltage regulator disabled, use external regulated 1.8V
supply voltage for the digital section
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• Bit 2 - DVDD_OK
This register bit indicates if the internal 1.8V regulated voltage supply DVDD has settled. The bit
is set to logic high, if DVREG_EXT = 1.
Table 9-8.
Regulated Voltage Supply Control for Digital Building Blocks
Register Bit
DVDD_OK
Value
Description
0
Digital voltage regulator disabled or supply voltage not stable
1
Digital supply voltage has settled
Note
• While the reset value of this bit is 0, any practical access to the register is only possible when
DVREG is active. So this bit is normally always read out as 1.
• Bit [1:0] - Reserved
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9.5
Battery Monitor (BATMON)
The main features of the battery monitor are:
• Configurable voltage threshold range: 1.7V to 3.675V
• Generates an interrupt when supply voltage drops below a threshold
9.5.1
Overview
The battery monitor (BATMON) detects and indicates a low supply voltage of the external supply
voltage at pin 28 (EVDD). This is done by comparing the voltage on the external supply pin 28
(EVDD) with a configurable internal threshold voltage. A simplified schematic of the BATMON
with the most important input and output signals is shown in Figure 9-6 on page 113.
Figure 9-6.
Simplified Schematic of BATMON
EVDD
BATMON_HR
+
DAC
4
BATMON_VTH
Threshold
Voltage
For input-to-output mapping
see control register
0x11 (BATMON)
BATMON_OK
-
„1“
clear
D
Q
BATMON_IRQ
9.5.2
Configuration
The BATMON can be configured using the register 0x11 (BATMON). Register subfield
BATMON_VTH sets the threshold voltage. It is configurable with a resolution of 75 mV in the
upper voltage range (BATMON_HR = 1) and with a resolution of 50 mV in the lower voltage
range (BATMON_HR = 0), for details refer to register 0x11 (BATMON).
9.5.3
Data Interpretation
The signal bit BATMON_OK of register 0x11 (BATMON) monitors the current value of the battery voltage:
• If BATMON_OK = 0, the battery voltage is lower than the threshold voltage
• If BATMON_OK = 1, the battery voltage is higher than the threshold voltage
After setting a new threshold, the value BATMON_OK should be read out to verify the current
supply voltage value.
Note, the battery monitor is inactive during P_ON and SLEEP states, see status register 0x01
(TRX_STATUS).
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9.5.4
Interrupt Handling
A supply voltage drop below the configured threshold value is indicated by an interrupt IRQ_7
(BAT_LOW), see Section 6.6 “Interrupt Logic” on page 29. Note that the interrupt is issued only
if BATMON_OK changes from 1 to 0.
No interrupt is generated when:
• The battery voltage is under the default 1.8V threshold at power up
(BATMON_OK was never 1), or
• A new threshold is set, which is still above the current supply voltage
(BATMON_OK remains 0).
When the battery voltage is close to the programmed threshold voltage, noise or temporary voltage drops may generate unwanted interrupts. To avoid this:
• Disable the IRQ_7 (BAT_LOW) in register 0x0E (IRQ_MASK) and treat the battery as
empty, or
• Set a lower threshold value.
9.5.5
Register Description
Register 0x11 (BATMON):
This register configures the battery monitor to compare the supply voltage at pin 28 (EVDD) to
the threshold BATMON_VTH. Additionally the supply voltage status at pin 28 (EVDD) is accessible by reading register bit BATMON_OK according to the actual BATMON settings.
Bit
7
+0x11
6
Reserved
5
4
3
2
1
0
BATMON_OK
BATMON_HR
Read/Write
R
R
R
R/W
R/W
R/W
BATMON_VTH
R/W
R/W
BATMON
Reset Value
0
0
0
0
0
0
1
0
• Bit [7:6] - Reserved
• Bit 5 - BATMON_OK
The register bit BATMON_OK indicates the level of the external supply voltage with respect to
the programmed threshold BATMON_VTH.
Table 9-9.
Register Bit
BATMON_OK
Battery Monitor Status
Value
Description
0
The battery voltage is below the threshold.
1
The battery voltage is above the threshold.
• Bit 4 - BATMON_HR
BATMON_HR sets the range and resolution of the battery monitor.
Table 9-10.
Register Bit
BATMON_HR
Battery Monitor Range Selection
Value
Description
0
Enables the low range, see BATMON_VTH
1
Enables the high range, see BATMON_VTH
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• Bit [3:0] - BATMON_VTH
The threshold values for the battery monitor are set by register bits BATMON_VTH:
Table 9-11.
Battery Monitor Threshold Voltage
Value
BATMON_VTH[3:0]
Voltage [V]
BATMON_HR = 1
Voltage [V]
BATMON_HR = 0
0x0
2.550
1.70
0x1
2.625
1.75
0x2
2.700
1.80
0x3
2.775
1.85
0x4
2.850
1.90
0x5
2.925
1.95
0x6
3.000
2.00
0x7
3.075
2.05
0x8
3.150
2.10
0x9
3.225
2.15
0xA
3.300
2.20
0xB
3.375
2.25
0xC
3.450
2.30
0xD
3.525
2.35
0xE
3.600
2.40
0xF
3.675
2.45
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9.6
Crystal Oscillator (XOSC)
The main crystal oscillator features are:
• 16 MHz amplitude controlled crystal oscillator
• 330 µs typical settling time after leaving SLEEP state
• Configurable trimming capacitance array
• Configurable clock output (CLKM)
9.6.1
Overview
The crystal oscillator generates the reference frequency for the AT86RF231. All other internally
generated frequencies of the radio transceiver are derived from this unique frequency. Therefore, the overall system performance is mainly determined by the accuracy of crystal reference
frequency. The external components of the crystal oscillator should be selected carefully and the
related board layout should be done with caution (see Section 5. “Application Circuits” on page
12).
The register 0x12 (XOSC_CTRL) provides access to the control signals of the oscillator. Two
operating modes are supported. It is recommended to use the integrated oscillator setup as
described in Figure 9-7 on page 116; nevertheless a reference frequency can be fed to the internal circuitry by using an external clock reference as shown in Figure 9-8 on page 117.
9.6.2
Integrated Oscillator Setup
Using the internal oscillator, the oscillation frequency depends on the load capacitance between
the crystal pins XTAL1 and XTAL2. The total load capacitance CL must be equal to the specified
load capacitance of the crystal itself. It consists of the external capacitors CX and parasitic
capacitances connected to the XTAL nodes.
Figure 9-7 on page 116 shows all parasitic capacitances, such as PCB stray capacitances and
the pin input capacitance, summarized to CPAR.
Figure 9-7.
Simplified XOSC Schematic with External Components
CPAR
CX
CX
CPAR
VDD
XTAL1
EVDD
16MHz
XTAL2
PCB
AT86RF231
CTRIM
CTRIM
XTAL_TRIM[3:0]
XTAL_TRIM[3:0]
EVDD
Additional internal trimming capacitors CTRIM are available. Any value in the range from 0 pF to
4.5 pF with a 0.3 pF resolution is selectable using XTAL_TRIM of register 0x12 (XOSC_CTRL).
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To calculate the total load capacitance, the following formula can be used:
CL = 0.5 * (CX + CTRIM + CPAR).
The trimming capacitors provide the possibility of reducing frequency deviations caused by production process variations or by external components tolerances. Note that the oscillation
frequency can only be reduced by increasing the trimming capacitance. The frequency deviation
caused by one step of CTRIM decreases with increasing crystal load capacitor values.
An amplitude control circuit is included to ensure stable operation under different operating conditions and for different crystal types. Enabling the crystal oscillator in P_ON state and after
leaving SLEEP state causes a slightly higher current during the amplitude build-up phase to
guarantee a short start-up time. At stable operation, the current is reduced to the amount necessary for a robust operation. This also keeps the drive level of the crystal low.
Generally, crystals with a higher load capacitance are less sensitive to parasitic pulling effects
caused by external component variations or by variations of board and circuit parasitics. On the
other hand, a larger crystal load capacitance results in a longer start-up time and a higher steady
state current consumption.
9.6.3
External Reference Frequency Setup
When using an external reference frequency, the signal must be connected to pin 26 (XTAL1) as
indicated in Figure 9-8 on page 117 and the register bits XTAL_MODE (register 0x12,
XOSC_CTRL) need to be set to the external oscillator mode. The oscillation peak-to-peak amplitude shall be between 100 mV and 500 mV, the optimum range is between 400 mV and 500 mV.
Pin 25 (XTAL2) should not be wired.
Figure 9-8.
Setup for Using an External Frequency Reference
16 MHz
XTAL1
XTAL2
PCB
AT86RF231
9.6.4
Master Clock Signal Output (CLKM)
The generated reference clock signal can be fed to a microcontroller using pin 17 (CLKM). The
internal 16 MHz raw clock can be divided by an internal prescaler. Thus, clock frequencies of
16 MHz, 8 MHz, 4 MHz, 2 MHz, 1 MHz, 250 kHz, or 62.5 kHz can be supplied by pin CLKM.
The CLKM frequency, update scheme, and pin driver strength is configurable using register
0x03 (TRX_CTRL_0). There are two possibilities how a CLKM frequency change gets effective.
If CLKM_SHA_SEL = 0 and/or CLKM_CTRL = 0, changing the register bits CLKM_CTRL immediately affects the CLKM clock rate. Otherwise (CLKM_SHA_SEL = 1 and CLKM_CTRL > 0
before changing the register bits CLKM_CTRL) the new clock rate is supplied when leaving the
SLEEP state the next time.
To reduce power consumption and spurious emissions, it is recommended to turn off the CLKM
clock when not in use or to reduce its driver strength to a minimum, refer to Section 1.3 “Digital
Pins” on page 7.
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Note:
• During reset procedure, see Section 7.1.2.8 “RESET State” on page 37, register bits CLKM_CTRL are
shadowed. Although the clock setting of CLKM remains after reset, a read access to register bits
CLKM_CTRL delivers the reset value 1. For that reason it is recommended to write the previous
configuration (before reset) to register bits CLKM_CTRL (after reset) to align the radio transceiver
behavior and register configuration. Otherwise the CLKM clock rate is set back to the reset value (1
MHz) after the next SLEEP cycle.
• For example, if the CLKM clock rate is configured to 16 MHz the CLKM clock rate remains at 16 MHz
after a reset, however the register bits CLKM_CTRL are set back to 1. Since CLKM_SHA_SEL reset
value is 1, the CLKM clock rate changes to 1 MHz after the next SLEEP cycle if the CLKM_CTRL
setting is not updated after reset.
9.6.5
Bit
Register Description
Register 0x03 (TRX_CTRL_0):
7
+0x03
6
5
PAD_IO
4
3
PAD_IO_CLKM
2
CLKM_SHA_SEL
1
0
CLKM_CTRL
TRX_CTRL_0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
1
1
0
0
1
The TRX_CTRL_0 register controls the drive current of the digital output pads and the CLKM
clock rate. It is recommended to use the lowest value for the drive current to reduce the current
consumption and the emission of signal harmonics.
• Bit [7:6] - PAD_IO
Refer to Section 1.3 “Digital Pins” on page 7.
• Bit [5:6] - PAD_IO_CLKM
These register bits set the output driver current of pin CLKM. It is recommended to reduce the
current capability to PAD_IO_CLKM = 0 (2 mA) if possible. This reduces power consumption
and spurious emissions.
Table 9-12.
CLKM Driver Strength
Register Bit
Value
PAD_IO_CLKM
Description
0
2 mA
1
4 mA
2
6 mA
3
8 mA
• Bit 3 - CLKM_SHA_SEL
Register bit CLKM_SHA_SEL defines if a new clock rate, defined by CLKM_CTRL, is set immediately or after the next SLEEP cycle.
Table 9-13.
CLKM Clock Rate Update Scheme
Register Bit
CLKM_SHA_SEL
Value
Description
0
CLKM clock rate change appears immediately
1
CLKM clock rate change appears after SLEEP cycle
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• Bit [2:0] - CLKM_CTRL
These register bits set clock rate of pin 17 (CLKM).
Table 9-14.
Clock Rate Setting at pin CLKM
Register Bit
Value
Description
CLKM_CTRL
0
No clock at pin 17 (CLKM), pin set to logic low
1
1 MHz
2
2 MHz
3
4 MHz
4
8 MHz
5
16 MHz
6
250 kHz
7
62.5 kHz (IEEE 802.15.4 symbol rate)
Register 0x12 (XOSC_CTRL):
The register XOSC_CTRL controls the operation of the crystal oscillator.
Bit
7
6
5
+0x12
4
3
2
XTAL_MODE
1
0
XTAL_TRIM
XOSC_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
0
0
0
0
• Bit [7:4] - XTAL_MODE
These register bits set the operating mode of the crystal oscillator. For normal operation the
default value is set to XTAL_MODE = 0xF after reset. Using an external clock source it is recommended to set XTAL_MODE = 0x4.
Table 9-15.
Crystal Oscillator Operating Mode
Register Bit
Value
Description
XTAL_MODE
0x4
Internal crystal oscillator disabled, use external reference frequency
0xF
Internal crystal oscillator enabled
XOSC voltage regulator enabled
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• Bit [3:0] - XTAL_TRIM
The register bits XTAL_TRIM control two internal capacitance arrays connected to pins XTAL1
and XTAL2. A capacitance value in the range from 0 pF to 4.5 pF is selectable with a resolution
of 0.3 pF.
Table 9-16.
Crystal Oscillator Trimming Capacitors
Register Bit
Value
Description
XTAL_TRIM
0x0
0.0 pF, trimming capacitors disconnected
0x1
0.3 pF trimming capacitor switched on
...
0xF
4.5 pF trimming capacitor switched on
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9.7
Frequency Synthesizer (PLL)
The main PLL features are:
• Generate RX/TX frequencies for all IEEE 802.15.4 - 2.4 GHz channels
• Autonomous calibration loops for stable operation within the operating range
• Two PLL-interrupts for status indication
• Fast PLL settling to support frequency hopping
9.7.1
Overview
The PLL generates the RF frequencies for the AT86RF231. During receive operation the frequency synthesizer works as a local oscillator on the radio transceiver receive frequency, during
transmit operation the voltage-controlled oscillator (VCO) is directly modulated to generate the
RF transmit signal. The frequency synthesizer is implemented as a fractional-N PLL.
Two calibration loops ensure correct PLL functionality within the specified operating limits.
9.7.2
RF Channel Selection
The PLL is designed to support 16 channels in the 2.4 GHz ISM band with a channel spacing of
5 MHz according to IEEE 802.15.4. The center frequency of these channels is defined as
follows:
Fc = 2405 + 5 (k - 11) in [MHz], for k = 11, 12,..., 26
where k is the channel number.
The channel k is selected by register bits CHANNEL (register 0x08, PHY_CC_CA).
9.7.3
Frequency Agility
When the PLL is enabled during state transition from TRX_OFF to PLL_ON, the settling time is
typically tTR4 = 110 µs, including settling of the analog voltage regulator (AVREG) and PLL self
calibration, refer to Table 7-2 on page 43 and Figure 13-13 on page 168. A lock of the PLL is
indicated with an interrupt IRQ_0 (PLL_LOCK).
Switching between 2.4 GHz ISM band channels in PLL_ON or RX_ON states is typically done
within tTR20 = 11 µs. This makes the radio transceiver highly suitable for frequency hopping
applications.
When starting the transmit procedure the PLL frequency is changed to the transmit frequency
within a period of tTR23 = 16 µs before starting the transmission. After the transmission the PLL
settles back to the receive frequency within a period of tTR24 = 32 µs. This frequency step does
not generate an interrupt IRQ_0 (PLL_LOCK) or IRQ_1 (PLL_UNLOCK) within these periods.
9.7.4
Calibration Loops
Due to variation of temperature, supply voltage and part-to-part variations of the radio transceiver the VCO characteristics may vary.
To ensure a stable operation, two automated control loops are implemented, center frequency
(CF) tuning and delay cell (DCU) calibration. Both calibration loops are initiated automatically
when the PLL is enabled during state transition from TRX_OFF to PLL_ON state. Additionally,
center frequency calibration is initiated when the PLL changes to a different channel center
frequency.
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If the PLL operates for a long time on the same channel, e.g. more than 5 min, or the operating
temperature changes significantly, it is recommended to initiate the calibration loops manually.
Both calibration loops can be initiated manually by setting PLL_CF_START = 1 (register 0x1A,
PLL_CF) and register bit PLL_DCU_START = 1 (register 0x1B, PLL_DCU). To start the calibration the device must be in PLL_ON or RX_ON state. The completion of the center frequency
tuning is indicated by a PLL_LOCK interrupt.
Both calibration loops may be run simultaneously.
9.7.5
Interrupt Handling
Two different interrupts indicate the PLL status (refer to register 0x0F). IRQ_0 (PLL_LOCK) indicates that the PLL has locked. IRQ_1 (PLL_UNLOCK) interrupt indicates an unexpected unlock
condition. A PLL_LOCK interrupt clears any preceding PLL_UNLOCK interrupt automatically
and vice versa.
A PLL_LOCK interrupt is supposed to occur in the following situations:
• State change from TRX_OFF to PLL_ON / RX_ON / TX_ARET_ON / RX_AACK_ON
• Channel change in states PLL_ON / RX_ON / TX_ARET_ON / RX_AACK_ON
Any other occurrences of PLL interrupts indicate erroneous behavior and require checking of the
actual device status.
The state transition from BUSY_TX to PLL_ON after successful transmission does not generate
an IRQ_0 (PLL_LOCK) within the settling period.
9.7.6
Register Description
Register 0x08 (PHY_CC_CCA):
This register sets the IEEE 802.15.4 - 2.4 GHz channel number
Bit
+0x08
7
6
CCA_REQUEST
5
4
3
CCA_MODE
2
1
0
CHANNEL
PHY_CC_CCA
Read/Write
W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
1
0
1
1
• Bit 7 - CCA_REQUEST
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94.
• Bit [6:5] - CCA_MODE
Refer to Section 8.5 “Clear Channel Assessment (CCA)” on page 94.
• Bit [4:0] - CHANNEL
The register bits CHANNEL define the RX/TX channel. The channel assignment is according to
IEEE 802.15.4.
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Table 9-17.
Channel Assignment for IEEE 802.15.4 - 2.4 GHz Band
Register Bit
Value
Channel Number k
Center Frequency [MHz]
CHANNEL
0x0B
11
2405
0x0C
12
2410
0x0D
13
2415
0x0E
14
2420
0x0F
15
2425
0x10
16
2430
0x11
17
2435
0x12
18
2440
0x13
19
2445
0x14
20
2450
0x15
21
2455
0x16
22
2460
0x17
23
2465
0x18
24
2470
0x19
25
2475
0x1A
26
2480
Register 0x1A (PLL_CF):
This register controls the operation of the center frequency calibration loop.
Bit
+0x1A
7
6
5
4
PLL_CF_START
3
2
1
0
Reserved
PLL_CF
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
1
0
1
0
1
1
1
• Bit 7 - PLL_CF_START
PLL_CF_START = 1 initiates the center frequency calibration. The calibration cycle has finished
after tTR21 = 35 µs (typ.). The register bit is cleared immediately after finishing the calibration.
• Bit [6:0] - Reserved
Register 0x1B (PLL_DCU):
This register controls the operation of the delay cell calibration loop.
Bit
+0x1B
7
6
5
4
PLL_DCU_START
3
2
1
0
Reserved
PLL_DCU
Read/Write
R/W
R
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
0
0
0
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• Bit 7 - PLL_DCU_START
PLL_DCU_START = 1 initiates the delay cell calibration. The calibration cycle has finished after
at most tTR22 = 6 µs, the register bit is set to 0. The register bit is cleared immediately after finishing the calibration.
• Bit [6:0] - Reserved
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9.8
Automatic Filter Tuning (FTN)
9.8.1
Overview
The FTN is incorporated to compensate device tolerances for temperature, supply voltage variations as well as part-to-part variations of the radio transceiver. The filter-tuning result is used to
correct the analog baseband filter transfer function and the PLL loop-filter time constant, refer to
Section 4. “General Circuit Description” on page 10.
An FTN calibration cycle is initiated automatically when entering the TRX_OFF state from the
SLEEP, RESET or P_ON states.
Although receiver and transmitter are very robust against these variations, it is recommended to
initiate the FTN manually if the radio transceiver does not use the SLEEP state. If necessary, a
calibration cycle is to be initiated in states TRX_OFF, PLL_ON or any receive state. This applies
in particular for the High Data Rate Modes with a much higher sensitivity against BPF transfer
function variations. The recommended calibration interval is 5 min or less.
9.8.2
Register Description
Register 0x18 (FTN_CTRL):
This register controls the operation of the filter tuning network calibration loop.
Bit
+0x18
7
6
5
4
FTN_START
3
2
1
0
Reserved
FTN_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
1
0
1
1
0
0
0
• Bit 7 - FTN_START
FTN_START = 1 initiates the filter tuning network calibration. When the calibration cycle has finished after at most 25 µs the register bit is automatically reset to 0.
• Bit [6:0] - Reserved
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10. Radio Transceiver Usage
This section describes basic procedures to receive and transmit frames using the AT86RF231.
For a detailed programming description refer to reference [6].
10.1
Frame Receive Procedure
A frame reception comprises of two actions: The PHY listens for, receives and demodulates the
frame to the Frame Buffer and signalizes the reception to the microcontroller. After or while that
the microcontroller read the available frame data from the Frame Buffer via the SPI interface.
While in state RX_ON or RX_AACK_ON the radio transceiver searches for incoming frames on
the selected channel. Assuming the appropriate interrupts are enabled, a detection of an
IEEE 802.15.4 compliant frame is indicated by interrupt IRQ_2 (RX_START) first. The frame
reception is completed when issuing interrupt IRQ_3 (TRX_END).
Different Frame Buffer read access scenarios are recommended for:
• Non-time critical applications
read access starts after IRQ_3 (TRX_END)
• Time-critical applications
read access starts after IRQ_2 (RX_START)
Waiting for IRQ_3 (TRX_END) interrupt before starting a Frame Buffer read access is recommended for operations considered to be none time critical. Figure 10-1 on page 126 illustrates
the frame receive procedure using IRQ_3 (TRX_END).
Figure 10-1. Transactions between AT86RF231 and Microcontroller during Receive
Read IRQ status, pin 24 (IRQ) deasserted
IRQ issued (IRQ_3)
Read IRQ status, pin 24 (IRQ) deasserted
Microcontroller
AT86RF231
IRQ issued (IRQ_2)
Read frame data (Frame Buffer access)
Critical protocol timing could require starting the Frame Buffer read access after interrupt
IRQ_2 (RX_START). The first byte of the frame data can be read 32 µs after the
IRQ_2 (RX_START) interrupt. The microcontroller must ensure to read slower than the frame is
received. Otherwise a Frame Buffer under run occurs, IRQ_6 (TRX_UR) is issued, and the
frame data may be not valid. To avoid this, the Frame Buffer read access can be controlled by
using a Frame Buffer Empty indicator, refer to Section 11.7 “Frame Buffer Empty Indicator” on
page 152.
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10.2
Frame Transmit Procedure
A frame transmission comprises of two actions, a Frame Buffer write access and the transmission of the Frame Buffer content. Both actions can be run in parallel if required by critical
protocol timing.
Figure 10-2 on page 127 illustrates the frame transmit procedure, when writing and transmitting
the frame consecutively. After a Frame Buffer write access, the frame transmission is initiated by
asserting pin 11 (SLP_TR) or writing command TX_START to register 0x02 (TRX_STATE),
while the radio transceiver is in state PLL_ON or TX_ARET_ON. The completion of the transaction is indicated by interrupt IRQ_3 (TRX_END).
Figure 10-2. Transaction between AT86RF231 and Microcontroller during Transmit
Write TRX_CMD = TX_START, or assert pin 11 (SLP_TR)
IRQ_3 (TRX_END) issued
Microcontroller
AT86RF231
Write frame data (Frame Buffer access)
Read IRQ_STATUS register, pin 24 (IRQ) deasserted
Alternatively a frame transmission can be started first, followed by the Frame Buffer write access
(PSDU data); refer to Figure 10-3 on page 127. This is applicable for time critical applications.
Initiating a transmission, either by asserting pin 11 (SLP_TR) or command TX_START to register bits TRX_CMD (register 0x02, TRX_STATE), the radio transceiver starts transmitting the
SHR, which is internally generated.
This first phase requires 16 µs for PLL settling and 160 µs for SHR transmission. The PHR must
be available in the Frame Buffer before this time elapses. Furthermore the SPI data rate must be
higher than the PHY data rate selected by register bits OQPSK_DATA_RATE (register 0x0C,
TRX_CTRL_2) to ensure that no Frame Buffer under run occurs, indicated by IRQ_6 (TRX_UR),
refer to Section 11.3 “High Data Rate Modes” on page 137.
Figure 10-3. Time Optimized Frame Transmit Procedure
Write frame data (Frame Buffer access)
IRQ_3 (TRX_END) issued
Microcontroller
AT86RF231
Write TRX_CMD = TX_START, or assert pin 11 (SLP_TR)
Read IRQ_STATUS register, pin 24 (IRQ) deasserted
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11. AT86RF231 Extended Feature Set
11.1
Security Module (AES)
The security module (AES) is characterized by:
• Hardware accelerated encryption and decryption
• Compatible with AES-128 standard (128-bit key and data block size)
• ECB (encryption/decryption) mode and CBC (encryption) mode support
• Stand-alone operation, independent of other blocks
11.1.1
Overview
The security module is based on an AES-128 core according to FIPS197 standard, refer to [5].
The security module works independent of other building blocks of the AT86RF231, encryption
and decryption can be performed in parallel to a frame transmission or reception.
Controlling the security block is implemented as an SRAM access to address space 0x82 to
0x94. A Fast SRAM access mode allows simultaneously writing new data and reading data from
previously processed data within the same SPI transfer. This access procedure is used to
reduce the turnaround time for ECB mode, see Section 11.1.5 “Data Transfer - Fast SRAM
Access” on page 132.
In addition, the security module contains another 128-bit register to store the initial key used for
security operations. This initial key is not modified by the security module.
11.1.2
Security Module Preparation
The use of the security module requires a configuration of the security engine before starting a
security operation. The following steps are required:
Table 11-1.
Step
AES Engine Configuration Steps
Description
Description
Section
1
Key Setup
Write encryption or decryption key to SRAM
Section 11.1.3
2
AES Mode
Select AES mode: ECB or CBC
Select encryption or decryption
Section 11.1.4.1
Section 11.1.4.2
3
Write Data
Write plaintext or cipher text to SRAM
Section 11.1.5
4
Start Operation
Start AES operation
5
Read Data
Read cipher text or plaintext from SRAM
Section 11.1.5
Before starting any security operation a key must be written to the security engine, refer to Section 11.1.3 “Security Key Setup” on page 129. The key set up requires the configuration of the
AES engine KEY mode using register bits AES_MODE (SRAM address 0x83, AES_CTRL).
The following step selects the AES mode, either electronic code book (ECB) or cipher block
chaining (CBC). These modes are explained more in detail in sections Section 11.1.4 “Security
Operation Modes” on page 129. Further, encryption or decryption must be selected with register
bit AES_DIR (SRAM address 0x83, AES_CTRL).
As next the 128-bit plain text or ciphertext data has to be provided to the AES hardware engine.
The data uses the SRAM address range 0x84 - 0x93.
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The encryption or decryption is initiated with register bit AES_REQUEST = 1 (SRAM address
0x83, AES_CTRL or the mirrored version with SRAM address 0x94, AES_CTRL_MIRROR).
The AES module control registers are only accessible using SRAM read and write accesses on
address space 0x82 to 0x94. A configuration of the AES mode, providing the data and the start
of the operation can be combined within one SRAM access.
Notes
• No additional register access is required to operate the security block.
• Using AES in TRX_OFF state requires an activated clock at pin 17 (CLKM), i.e. register bits
CLKM_CTRL!= 0. For further details refer to Section 9.6.4 “Master Clock Signal Output
(CLKM)” on page 117.
• Access to the security block is not possible while the radio transceiver is in state SLEEP.
• All configurations of the security module, the SRAM content and keys are reset during
SLEEP or RESET states.
11.1.3
Security Key Setup
The setup of the key is prepared by setting register bits AES_MODE = 0x1 (SRAM address
0x83, AES_CTRL). Afterwards the 128 bit key must be written to SRAM addresses 0x84 through
0x93 (registers AES_KEY). It is recommended to combine the setting of control register 0x83
(AES_CTRL) and the 128 bit key transfer using only one SRAM access starting from address
0x83.
The address space for the 128-bit key and 128-bit data is identical from programming point of
view. However, both use different pages which are selected by register bit AES_MODE before
storing the data.
A read access to registers AES_KEY (0x84 - 0x93) returns the last round key of the preceding
security operation. After an ECB encryption operation, this is the key that is required for the corresponding ECB decryption operation. However, the initial AES key, written to the security
module in advance of an AES run, see step 1 in Table 11-1 on page 128, is not modified during
an AES operation. This initial key is used for the next AES run even it cannot be read from
AES_KEY.
Note
• ECB decryption is not required for IEEE 802.15.4 or ZigBee security processing. The
AT86RF231 provides this functionality as an additional feature.
11.1.4
11.1.4.1
Security Operation Modes
Electronic Code Book (ECB)
ECB is the basic operating mode of the security module. After setting up the initial AES key, register bits AES_MODE = 0 (SRAM address 0x83, AES_CTRL) sets up ECB mode. Register bit
AES_DIR (SRAM address 0x83, AES_CTRL) selects the direction, either encryption or decryption. The data to be processed has to be written to SRAM addresses 0x84 through 0x93
(registers AES_STATE).
An example for a programming sequence is shown in Figure 11-1 on page 130. This example
assumes a suitable key has been loaded before.
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A security operation can be started within one SRAM access by appending the start command
AES_REQUEST = 1 (register 0x94, AES_CTRL_MIRROR) to the SPI sequence. Register
AES_CTRL_MIRROR is a mirrored version of register 0x83 (AES_CTRL).
Figure 11-1. ECB Programming SPI Sequence - Encryption
byte 0 (cmd.)
byte 1 (address)
byte 2 (AES cmd)
0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
SRAM write
0x83
byte 3 (data)
byte 18 (data)
byte 19 (AES cmd)
data_0[7:0]
data_15[7:0]
1 0 0 0 0 0 0 0
ECB, encryption
AES start
Summarizing, the following steps are required to perform a security operation using only one
SPI access:
1. Configure SPI Access
a) SRAM Write, refer to Section 6.2.3
b) Start Address 0x83
2. Configure AES Operation
Address 0x83: select ECB mode, direction
3. Write 128-bit data block
Addresses 0x84 - 0x93: either plain or ciphertext
4. Start AES Operation
Addresses 0x94: start AES operation, ECB mode
This sequence is recommended because the security operation is configured and started within
one SPI transaction.
The ECB encryption operation is illustrated in Figure 11-2 on page 130. Figure 11-3 on page 130
shows the ECB decryption mode, which is supported in a similar way.
Figure 11-2. ECB Mode - Encryption
Plaintext
Encryption
Key
Block Cipher
Encryption
Plaintext
Encryption
Key
Ciphertext
Block Cipher
Encryption
Ciphertext
Figure 11-3. ECB Mode - Decryption
Ciphertext
Decryption
Key
Block Cipher
Decryption
Plaintext
Ciphertext
Decryption
Key
Block Cipher
Decryption
Plaintext
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When decrypting, due to the nature of AES algorithm, the initial key to be used is not the same
as the one used for encryption, but rather the last round key instead. This last round key is the
content of the key address space stored after running one full encryption cycle, and must be
saved for decryption. If the decryption key has not been saved, it has to be recomputed by first
running a dummy encryption (of an arbitrary plaintext) using the original encryption key, then
fetching the resulting round key from the key memory, and writing it back into the key memory as
the decryption key.
ECB decryption is not used by either IEEE 802.15.4 or ZigBee frame security. Both of these
standards do not directly encrypt the payload, but rather a nonce instead, and protect the payload by applying an XOR operation between the resulting (AES-) cipher text and the original
payload. As the nonce is the same for encryption and decryption only ECB encryption is
required. Decryption is performed by XORing the received cipher text with its own encryption
result respectively, which results in the original plaintext payload upon success.
11.1.4.2
Cipher Block Chaining (CBC)
In CBC mode, the result of a previous AES operation is XORed with the new incoming vector,
forming the new plaintext to encrypt, see Figure 11-4 on page 131. This mode is used for the
computation of a cryptographic checksum (message integrity code, MIC).
Figure 11-4. CBC Mode - Encryption
Plaintext
Encryption
Key
Initialization Vector (IV)
Block Cipher
Encryption
Encryption
Key
Plaintext
Block Cipher
Encryption
Ciphertext
Ciphertext
ECB
mode
CBC
mode
After preparing the AES key, and defining the AES operation direction using SRAM register bit
AES_DIR, the data has to be provided to the AES engine and the CBC operation can be started.
The first CBC run has to be configured as ECB to process the initial data (plaintext XORed with
an initialization vector provided by the microcontroller). All succeeding AES runs are to be configured as CBC by setting register bits AES_MODE = 0x2 (register 0x83, AES_CTRL). Register
bit AES_DIR (register 0x83, AES_CTRL) must be set to AES_DIR = 0 to enable AES encryption.
The data to be processed has to be transferred to the SRAM starting with address 0x84 to 0x93
( r e g i s t e r A E S _ S T AT E ) . S e t t i n g r e g i s t e r b i t A E S _ R E Q U E S T = 1 ( r e g i s t e r 0 x 9 4 ,
AES_CTRL_MIRROR) as described in Section 11.1.4 “Security Operation Modes” on page 129
starts the first encryption within one SRAM access. This causes the next 128 bits of plaintext
data to be XORed with the previous cipher text data, see Figure 11-4 on page 131.
According to IEEE 802.15.4 the input for the very first CBC operation has to be prepared by a
XORing a plaintext with an initialization vector (IV). The value of the initialization vector is 0.
However, for non-compliant usage any other initialization vector can be used. This operation has
to be prepared by the microcontroller.
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Note that IEEE 802.15.4-2006 standard MIC algorithm requires CBC mode encryption only, as it
implements a one-way hash function.
11.1.5
Data Transfer - Fast SRAM Access
The ECB and CBC modules including the AES core are clocked with 16 MHz. One AES operation takes 24 µs to execute, refer to parameter 12.4.15 in Section 12.4 “Digital Interface Timing
Characteristics” on page 157. That means that the processing of the data is usually faster than
the transfer of the data via the SPI interface.
To reduce the overall processing time the AT86RF231 provides a Fast SRAM access for the
address space 0x82 to 0x94.
Figure 11-5. Packet Structure - Fast SRAM Access Mode
AES run #n
AES run #0
MOSI
cmd add cfg P0 P1
MISO
stat xx
Address
xx
xx
0x83
xx
AES access #1
... P14 P15 start
cmd add cfg P0 P1
...
stat xx
xx
...
xx
xx
0x94
xx
xx
0x83
C0
AES access #n+1
... P14 P15 start
... C13 C14 C15
...
byte 1 (addr.)
byte 2 (cfg)
byte 3
byte 4
MOSI
SRAM write
address 0x83
<AES_CTRL>
P0[7:0]
P1[7:0]
MISO
PHY_STATUS
XX
XX
XX
C0[7:0]
0x83
0x84
0x85
Note:
cmd add cfg xx
stat xx
xx
0x83
0x94
byte 0 (cmd)
Address
...
AES access #0
xx
xx C0
...
xx
xx start
... C13 C14 C15
...
byte 18
byte 19 (start)
...
P15[7:0]
<AES_CTRL>(1)
...
C14[7:0]
C15[7:0]
0x93
0x94
0x94
Byte 19 is the mirrored version of register AES_CTRL on SRAM address 0x94, see register
description AES_CTRL_MIRROR for details.
In contrast to a standard SRAM access, refer to Section 6.2.3 “SRAM Access Mode” on page
22, the Fast SRAM access allows writing and reading of data simultaneously during one SPI
access for consecutive AES operations (AES run).
For each byte P0 transferred to pin 22 (MOSI) for example in "AES access #1", see Figure 11-5
on page 132 (lower part), the previous content of the respective AES register C0 is clocked out
at pin 20 (MISO) with an offset of one byte.
In the example shown in Figure 11-5 on page 132 the initial plaintext P0 - P15 is written to the
SRAM within "AES access #0". The last command on address 0x94 (AES_CTRL_MIRROR)
starts the AES operation ("AES run #0"). In the next "AES access #1" new plaintext data P0 P15 is written to the SRAM for the second AES run, in parallel the ciphertext C0 - C15 from the
first AES run is clocked out at pin MISO. To read the ciphertext from the last "AES run #(n)" one
dummy "AES access #(n+1)" is needed.
Note that the SRAM write access always overwrites the previous processing result.
The Fast SRAM access automatically applies to all write operations to SRAM addresses 0x82 to
0x94.
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11.1.6
Start of Security Operation and Status
A security operation is started within one SRAM access by appending the start command
AES_REQUEST = 1 (register 0x94, AES_CTRL_MIRROR) to the SPI sequence. Register
AES_CTRL_MIRROR is a mirrored version of register 0x83 (AES_CTRL).
The status of the security processing is indicated by register 0x82 (AES_STATUS). After 24 µs
AES processing time register bit AES_DONE changes to 1 (register 0x82, AES_STATUS) indicating that the security operation has finished, see parameter 12.4.15 in Section 12.4 “Digital
Interface Timing Characteristics” on page 157.
11.1.7
SRAM Register Summary
The following registers are required to control the security module:
Table 11-2.
SRAM Security Module Address Space Overview
SRAM-Addr.
Register Name
Description
0x80 - 0x81
Reserved, not available
0x82
AES_STATUS
AES Status
0x83
AES_CTRL
Security Module Control, AES Mode
0x84 - 0x93
Depends on AES_MODE setting:
AES_MODE = 1:
- Contains AES_KEY (key)
AES_MODE = 0 | 2:
- Contains AES_STATE (128-bit data block)
AES_KEY
AES_STATE
AES_CTRL_MIRROR
0x94
Mirror of register 0x83 (AES_CTRL)
0x95 - 0xFF
Reserved, not available
These registers are only accessible using SRAM write and read accesses, for details refer to
Section 6.2.3 “SRAM Access Mode” on page 22. Note, that the SRAM register are reset when
entering the SLEEP state.
11.1.8
AES SRAM Configuration Register
Register 0x82 (AES_STATUS):
This read-only register signals the status of the security module and operation.
Bit
+0x82
7
6
5
4
AES_ER
3
2
1
Reserved
0
AES_DONE
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
AES_STATUS
• Bit 7 - AES_ER
This SRAM register bit indicates an error of the AES module. An error may occur for instance
after an access to SRAM register 0x83 (AES_CTRL) while an AES operation is running or after
reading less than 128 bits from SRAM register space 0x84 - 0x93 (AES_STATE).
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Table 11-3.
AES Core Operation Status
Register Bit
Value
AES_ER
Description
0
No error of the AES module
1
AES module error
• Bit [6:1] -Reserved
• Bit 0 - AES_DONE
Table 11-4.
AES Core Operation Status
Register Bit
Value
Description
AES_DONE
0
AES Module is not finished
1
AES module has finished
Register 0x83 (AES_CTRL):
This register controls the operation of the security module. Do not access this register during
AES operation to read the AES core status. A read or write access during AES operation stops
the actual processing.
To read the AES status use register bit AES_DONE (register 0x82, AES_STATUS).
Bit
+0x83
7
6
AES_REQUEST
5
4
AES_MODE
3
2
AES_DIR
1
0
Reserved
AES_CTRL
Read/Write
W
R/W
R/W
R/W
R/W
R
R
R
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - AES_REQUEST
A write access with AES_REQUEST = 1 initiates the AES operation.
Table 11-5.
AES Core Status
Register Bit
Value
AES_REQUEST
Description
0
Security module, AES core idle
1
Write access: Start security module
• Bit [6:4] - AES_MODE
This register bit sets the AES operation mode.
Table 11-6.
AES Mode
Register Bit
Value
AES_MODE
0
ECB mode, refer to Section 11.1.4.1
1
KEY mode, refer to Section 11.1.3
2
CBC mode, refer to Section 11.1.4.2
3-7
Description
Reserved
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• Bits 3 - AES_DIR
This register bit sets the AES operation direction, either encryption or decryption.
Table 11-7.
AES Direction
Register Bit
Value
AES_DIR
Description
0
AES encryption (ECB, CBC)
1
AES decryption
• Bit [2:0] - Reserved
Register 0x94 (AES_CTRL_MIRROR):
Register 0x94 is a mirrored version of register 0x83 (AES_CTRL), for details refer to register
0x83 (AES_CTRL).
Bit
+0x83
7
6
AES_REQUEST
5
4
AES_MODE
3
2
AES_DIR
1
0
Reserved
AES_CTRL
Read/Write
W
R/W
R/W
R/W
R/W
R
R
R
Reset Value
0
0
0
0
0
0
0
0
This register could be used to start a security operation within a single SRAM access by appending it to the data stream and setting register bit AES_REQUEST = 1.
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11.2
11.2.1
Random Number Generator
Overview
The AT86RF231 incorporates a 2-bit truly random number generator by observation of noise.
This random number can be used to:
• Generate random seeds for CSMA-CA algorithm
see Section 7.2
• Generate random values for AES key generation
see Section 11.1
The random number is updated every tTR29 = 1 µs in Basic Operation Mode receive states. The
values are stored in register bits RND_VALUE (register 0x06, PHY_RSSI).
11.2.2
Register Description
Register 0x06 (PHY_RSSI):
Register 0x06 (PHY_RSSI) is a multi purpose register to indicate FCS validity, to provide random numbers and an RSSI value.
Bit
7
+0x06
RX_CRC_VALID
6
5
4
3
RND_VALUE
2
1
0
RSSI
PHY_RSSI
Read/Write
R
R
R
R
R
R
R
R
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - RX_CRC_VALID
Refer to register description in Section 8.2.5 “Register Description” on page 87.
• Bit [6:5] - RND_VALUE
The 2-bit random value can be retrieved by reading register bits RND_VALUE. Note that the
radio transceiver shall be in Basic Operating Mode receive state. The values are updated each
tTR29 = 1 µs.
• Bit [4:0] - RSSI
Refer to register description in Section 8.3.4 “Register Description” on page 90.
Note:
Ensure that register bit RX_PDT_DIS (register 0x15, RX_SYN) is set to 0 at least 1 µs before
reading a random value.
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11.3
High Data Rate Modes
The main features are:
• High Data Rate Transmission up to 2 Mb/s.
• Support of Basic and Extended Operating Mode
• Support of other features of the Extended Feature Set
• Reduced ACK timing (optional)
11.3.1
Overview
The AT86RF231 also supports alternative data rates, higher than 250 kb/s for applications
beyond IEEE 802.15.4 compliant networks.
The selection of a data rate does not affect the remaining functionality. Thus it is possible to run
all features and operating modes of the radio transceiver in various combinations.
The data rate can be selected by writing to register bits OQPSK_DATA_RATE (register 0x0C,
TRX_CTRL_2).
The High Data Rate Modes occupy the same RF channel bandwidth as the IEEE 802.15.42.4 GHz 250 kb/s standard mode. Due to the decreased spreading factor, the sensitivity of the
receiver is reduced accordingly. Table 11-8 on page 137 shows typical values of the sensitivity
for different data rates.
Table 11-8.
High Data Rate Sensitivity
High Data Rate
Sensitivity
Comment
250 kb/s
-101 dBm
PER ≤ 1%, PSDU length of 20 octets
500 kb/s
-97 dBm
PER ≤ 1%, PSDU length of 20 octets
1000 kb/s
-95 dBm
PER ≤ 1%, PSDU length of 20 octets
2000 kb/s
-89 dBm
PER ≤ 1%, PSDU length of 20 octets
By default there is no header based signaling of the data rate within a transmitted frame. Thus
nodes using a data rate other than the default IEEE 802.15.4 data rate of 250 kb/s are to be configured in advance and consistently. Alternatively the configurable start of frame delimiter (SFD)
could be used as an indicator of the PHY data rate, see Section 11.9 “Configurable Start-OfFrame Delimiter” on page 155.
11.3.2
High Data Rate Packet Structure
In order to allow appropriate frame synchronization, higher data rate modulation is restricted to
the payload octets only. The SHR and the PHR field are transmitted with the IEEE 802.15.4
compliant data rate of 250 kb/s, refer to Section 8.1.1 “PHY Protocol Layer Data Unit (PPDU)”
on page 79.
A comparison of the general packet structure for different data rates with an example PSDU
length of 80 octets is shown in Figure 11-6 on page 138.
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Figure 11-6. High Data Rate Frame Structure
500 kb/s
PSDU: 80 octets
1000 kb/s
PSDU: 80 octets
2000 kb/s
PSDU: 80 octets
1472
2752 time [µs]
FCS
SFD
PHR
PSDU: 80 octets
832
FCS
250 kb/s
SFD
PHR
512
SFD
PHR
192
SFD
PHR
0
Due to the overhead caused by the SHR, PHR as well as the FCS, the effective data rate is
lower than the selected data rate. This is also affected by the length of the PSDU. A graphical
representation of the effective PSDU data rate is shown in Figure 11-7 on page 138.
Figure 11-7. Effective Data Rate "B" for High Data Rate Mode
1600
2000
1000
500
250
1400
1200
B [kb/s ]
1000
2000 kb/s
800
1000 kb/s
600
500 kb/s
400
250 kb/s
200
0
0
20
40
60
80
100
120
PSDU length in octets
The effective throughput is further affected by the MAC overhead, the acknowledgment scheme
as well as the MCU processing capability. Consequently, High Data Rate transmission and
reception is useful for large PSDU lengths due to the higher effective data rate, or to reduce the
power consumption of the system. When using High Data Rate Modes the active on-air time is
significantly reduced.
11.3.3
High Data Rate Frame Buffer Access
The Frame Buffer access to read or write frames for High Data Rate transmission is similar to
the procedure described in Section 6.2.2 “Frame Buffer Access Mode” on page 20. However,
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during Frame Buffer read access the last byte transferred after the PSDU data is the ED value
rather than the LQI value.
Figure 11-8 on page 139 illustrates the packet structure of a High Data Rate Frame Buffer read
access.
Figure 11-8. Packet Structure - High Data Rate Frame Buffer Read Access
11.3.4
byte 1 (command byte)
byte 2 (data byte)
byte 3 (data byte)
byte n-1 (data byte)
byte n (data byte)
MOSI
0 0 1 reserved[5:0]
XX
XX
XX
XX
MISO
PHY_STATUS
PHR[7:0]
PSDU[7:0]
PSDU[7:0]
ED[7:0]
High Data Rate Energy Detection
According to IEEE 802.15.4 the ED measurement duration is 8 symbol periods. For frames
operated at higher data rates the automated ED measurement duration is reduced to 32 µs to
take the reduced frame length into account, refer to Section 8.4 “Energy Detection (ED)” on
page 91.
During Frame Buffer read access the ED value is appended to the PSDU data, refer to Section
11.3.3 “High Data Rate Frame Buffer Access” on page 138.
11.3.5
High Data Rate Mode Options
Receiver Sensitivity Control
The different data rates between PPDU header (SHR and PHR) and PHY payload (PSDU)
cause a different sensitivity between header and payload. This can be adjusted by defining sensitivity threshold levels of the receiver. With a sensitivity threshold level set (register bits
RX_PDT_LEVEL > 0), the receiver does not receive frames with an RSSI level below that
threshold. Under these operating conditions the receiver current consumption is reduced by
about 500 µA, refer to Section 12.8 “Current Consumption Specifications” on page 161 parameter 12.8.4.
Enabling receiver sensitivity control with at least RX_PDT_LEVEL = 1 is recommended for the 2
Mb/s rate with a PSDU sensitivity of -89 dBm. In the case of receiving with the default setting of
RX_PDT_LEVEL, a high data rate frame may be detected even if the PSDU sensitivity is above
the received signal strength. In this case the frame is rejected.
A description of the settings to control the sensitivity threshold with register 0x15 (RX_SYN) can
be found in Section 9.1.4 “Register Description” on page 103.
Reduced Acknowledgment Timing
On higher data rates the IEEE 802.15.4 compliant acknowledgment frame response time of
192 µs significantly reduces the effective data rate of the network. To minimize this influence in
Extended Operating Mode RX_AACK, refer to Section 7.2.3 “RX_AACK_ON - Receive with
Automatic ACK” on page 51, the acknowledgment frame response time can be reduced to
32 µs. Figure 11-9 on page 140 illustrates an example for a reception and acknowledgement of
a frame with a data rate of 2000 kb/s and a PSDU length of 80 symbols. The PSDU length of the
acknowledgment frame is 5 octets according to IEEE 802.15.4.
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Figure 11-9. High Data Rate AACK Timing
704
916
SFD
192 µs
PHR
PSDU: 80 octets
544
SFD
SFD
PHR
SFD
AACK_ACK_TIME = 1
PSDU: 80 octets
PHR
AACK_ACK_TIME = 0
512
192
PHR
0
time [µs]
ACK
ACK
32 µs
If register bit AACK_ACK_TIME (register 0x17, XAH_CTRL_1) is set the acknowledgment time
is reduced from 192 µs to 32 µs.
11.3.6
Register Description
Register 0x0C (TRX_CTRL_2):
The TRX_CTRL_2 register controls the data rate setting
Bit
+0x0C
7
6
5
RX_SAFE_MODE
4
3
2
1
Reserved
0
OQPSK_DATA_RATE
TRX_CTRL_2
Read/Write
R/W
R
R
R
R
R
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - RX_SAFE_MODE
Refer to Section 11.8.2 “Register Description” on page 154.
• Bit [6:2] - Reserved
• Bit [1:0] - OQPSK_DATA_RATE
A write access to these register bits sets the OQPSK PSDU data rate used by the radio transceiver. The reset value OQPSK_DATA_RATE = 0 is the PSDU data rate according to
IEEE 802.15.4.
Table 11-9.
OQPSK Data Rate
Register Bits
OQPSK_DATA_RATE
Value
OQPSK Data Rate
0
250 kb/s
1
500 kb/s
2
1000 kb/s
3
2000 kb/s
Comment
IEEE 802.15.4 compliant
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Register 0x17 (XAH_CTRL_1):
The XAH_CTRL_1 register is a multi-purpose control register for various RX_AACK settings.
Bit
7
+0x17
6
Reserved
5
4
3
2
1
0
AACK_FLTR_RES_FT
AACK_UPLD_RES_FT
Reserved
AACK_ACK_TIME
AACK_PROM_MODE
Reserved
Read/Write
R/W
R
R/W
R/W
R
R/W
R/W
R
Reset Value
0
0
1
0
0
0
0
0
XAH_CTRL_1
• Bit [7:6] - Reserved
• Bit 5 - AACK_FLTR_RES_FT
Refer to 7.2.7 “Register Description - Control Registers” on page 68.
• Bit 4 - AACK_UPLD_RES_FT
Refer to Section 7.2.7 “Register Description - Control Registers” on page 68.
• Bit 3 - Reserved
• Bit 2 - AACK_ACK_TIME
According to IEEE 802.15.4, section 7.5.6.4.2 the transmission of an acknowledgment frame
shall commence 12 symbol periods (aTurnaroundTime) after the reception of the last symbol of
a data or MAC command frame. This is fulfilled with the reset value of the register bit [2]
(AACK_ACK_TIME).
If AACK_ACK_TIME = 1 an acknowledgment frame is sent 32 µs after the reception of the last
symbol of a data or MAC command frame. This may be applied to proprietary networks including
networks using the High Data Rate Modes to improve the overall data throughput.
• Bit 1 - AACK_PROM_MODE
Refer to Section 7.2.7 “Register Description - Control Registers” on page 68.
• Bit 0 - Reserved
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11.4
Antenna Diversity
The Antenna Diversity implementation is characterized by:
• Improves signal path robustness between nodes
• AT86RF231 self-contained antenna diversity algorithm
• Direct register based antenna selection
11.4.1
Overview
Due to multipath propagation effects between network nodes, the receive signal strength may
vary and affect the link quality, even for small changes of the antenna location. These fading
effects can result in an increased error floor or loss of the connection between devices.
To improve the reliability of an RF connection between network nodes Antenna Diversity can be
applied to reduce effects of multipath propagation and fading. Antenna Diversity uses two antennas to select the most reliable RF signal path. This is done by the radio transceiver during
preamble field search without the need for microcontroller interaction. To ensure highly independent receive signals on both antennas, the antennas should be carefully separated from each
other.
If a preamble field is detected on one antenna, this antenna is selected for reception. Otherwise
the search is continued on the other antenna and vice versa.
Antenna Diversity can be used in Basic and Extended Operating Modes and can also be combined with other features and operating modes like High Data Rate Mode and RX/TX Indication.
11.4.2
Antenna Diversity Application Example
A block diagram for an application using an antenna switch is shown in Figure 11-10 on page
142.
Figure 11-10. Antenna Diversity - Block Diagram
ANT0
1
DIG3
AT86RF231
2 DIG4
3 AVSS
4 RFP
6 AVSS
...
DIG2
5 RFN
DIG1
B1
Balun
RFSwitch
SW1
9
10
ANT1
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Generally, the Antenna Diversity algorithm is enabled with register bit ANT_DIV_EN (register
0x0D, ANT_DIV) set. In this case the control of an antenna diversity switch must be enabled by
register bit ANT_EXT_SW_EN (register 0x0D, ANT_DIV). The internal connection to digital
ground of the control pins pin 9 (DIG1) and pin 10 (DIG2) is disabled (refer to section 4.2), and
they feed the antenna switch signal and its inverse to the differential inputs of the RF Switch
(SW1).
Upon reception of a frame the AT86RF231 selects one antenna during preamble field detection.
The selected antenna is then indicated by register bit ANT_SEL (register 0x0D, ANT_DIV). After
the frame reception is completed, the antenna selection continues searching for new frames on
both antennas. However, the register bit ANT_SEL maintains its previous value (from the last
received frame) until a new SHR has been found, and the selection algorithm locked into one
antenna again. At this time the register bit ANT_SEL is updated again.
For transmission the antenna defined by register bits ANT_CTRL (register 0x0D, ANT_DIV) is
selected. If for example the same antenna is to be used for transmission as being selected for
reception, the antenna must be set using register bits ANT_CTRL, based on the value read from
register bit ANT_SEL. It is recommended to read register bit ANT_SEL after
IRQ_2 (RX_START).
The autonomous search and selection allows the use of Antenna Diversity during reception
even if the microcontroller does currently not control the radio transceiver, for instance in
Extended Operating Mode.
A microcontroller defined selection of a certain antenna can be done by disabling the automated
Antenna Diversity algorithm (ANT_DIV_EN = 0) and selecting one antenna using register bit
ANT_CTRL.
If the AT86RF231 is not in a receive or transmit state, it is recommended to disable register bit
ANT_EXT_SW_EN to reduce the power consumption or avoid leakage current of an external RF
switch, especially during SLEEP state. If register bit ANT_EXT_SW_EN = 0, output pins
DIG1/DIG2 are pulled-down to digital ground.
11.4.3
Antenna Diversity Sensitivity Control
Due to a different receive algorithm used by the Antenna Diversity algorithm, the correlator
threshold of the receiver has to be adjusted. It is recommended to set register bits PDT_THRES
(register 0x0A, RX_CTRL) to 3.
11.4.4
Register Description
Register 0x0A (RX_CTRL):
The RX_CTRL controls the sensitivity of the Antenna Diversity Mode
Bit
7
6
+0x0A
5
4
3
2
Reserved
1
0
PDT_THRES
RX_CTRL
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
0
1
1
0
1
1
1
• Bit [7:4] - Reserved
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• Bit [3:0] - PDT_THRES
These register bits control the sensitivity of the receiver correlation unit. If the Antenna Diversity
algorithm is enabled (ANT_DIV_EN = 1), the value shall be set to PDT_THRES = 3, otherwise it
shall be set back to the reset value. This is not automatically done by the hardware.
Table 11-10. Receiver Sensitivity Control
Register Bit
Value
Description
PDT_THRES
0x7
Reset value, to be used if Antenna Diversity algorithm is disabled
0x3
Recommended correlator threshold for Antenna Diversity operation
Other
Reserved
Register 0x0D (ANT_DIV):
The ANT_DIV register controls Antenna Diversity.
Bit
+0x0D
7
6
ANT_SEL
5
4
Reserved
3
2
ANT_DIV_EN
ANT_EXT_SW_EN
1
0
ANT_CTRL
ANT_DIV
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Reset Value
0
0
0
0
0
0
1
1
• Bit 7 - ANT_SEL
This register bit signals the currently selected antenna path. The selection may be based either
on the last antenna diversity cycle (ANT_DIV_EN = 1) or on the content of register bits
ANT_CTRL, for details refer to Section 11.4.2 “Antenna Diversity Application Example” on page
142.
Table 11-11. Antenna Diversity - Antenna Status
Register Bit
Value
ANT_SEL
Description
0
Antenna 0
1
Antenna 1
• Bit [6:4] - Reserved
• Bit 3 - ANT_DIV_EN
If register bit ANT_DIV_EN is set, the Antenna Diversity algorithm is enabled. On reception of a
frame the algorithm selects an antenna autonomously during SHR search. This selection is kept
until:
• A new SHR search starts
• Leaving receive states
• Manually programmed register bits ANT_CTRL
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Table 11-12. Antenna Diversity Control
Register Bit
Value
ANT_DIV_EN
0
Antenna Diversity algorithm disabled
1
Antenna Diversity algorithm enabled
Note:
Description
If ANT_DIV_EN = 1 register bit ANT_EXT_SW_EN shall be set to 1, too. This is not automatically
done by the hardware.
• Bit 2 - ANT_EXT_SW_EN
If enabled, pin 9 (DIG1) and pin 10 (DIG2) become output pins and provide a differential control
signal for an Antenna Diversity switch. The selection of a specific antenna is done either by the
automated Antenna Diversity algorithm (ANT_DIV_EN = 1), or according to register bits
ANT_CTRL if Antenna Diversity algorithm is disabled.
Do not enable Antenna Diversity RF switch control (ANT_EXT_SW_EN = 1) and RX Frame
Time Stamping (IRQ_2_EXT_EN = 1) at the same time, see Section 11.6 “RX Frame Time
Stamping” on page 150.
If the register bit is set the control pins DIG1/DIG2 are activated in all radio transceiver states as
long as register bit ANT_EXT_SW_EN is set. If the AT86RF231 is not in a receive or transmit
state, it is recommended to disable register bit ANT_EXT_SW_EN to reduce the power consumption or avoid leakage current of an external RF switch, especially during SLEEP state. If
register bit ANT_EXT_SW_EN = 0, output pins DIG1 and DIG2 are pulled-down to digital
ground.
Table 11-13. Antenna Diversity RF Switch Enable
Register Bit
Value
Description
ANT_EXT_SW_EN
0
Antenna Diversity RF Switch Control disabled
1
Antenna Diversity RF Switch Control enabled
Note:
If ANT_EXT_SW_EN = 0, register bit ANT_DIV_EN shall be set to 0 and register bits ANT_CTRL
to 3. This is not automatically done by the hardware.
• Bit [1:0] - ANT_CTRL
These register bits provide a static control of an Antenna Diversity switch. Setting
ANT_DIV_EN = 0 (Antenna Diversity disabled), this register setting defines the selected
antenna. Although it is possible to change register bits ANT_CTRL in state TRX_OFF, this
change will be effective at pins DIG1 and DIG2 in state PLL_ON as well as all receive and transmit states.
Table 11-14. Antenna Diversity Switch Control
Register Bit
Value
Description
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Table 11-14. Antenna Diversity Switch Control
ANT_CTRL
Note:
0
Reserved
1
Antenna 1
DIG1 = L
DIG2 = H
2
Antenna 0
DIG1 = H
DIG2 = L
3
Default value for ANT_EXT_SW_EN = 0.
Mandatory setting for applications not using Antenna Diversity.
Register values 1 and 2 are valid for ANT_EXT_SW_EN = 1.
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11.5
RX/TX Indicator
The main features are:
• RX/TX Indicator to control an external RF Front-End
• Microcontroller independent RF Front-End Control
• Provide TX Timing Information
11.5.1
Overview
While IEEE 802.15.4 is a low cost, low power standard, solutions supporting higher transmit output power are occasionally desirable. To simplify the control of an optional external RF frontend, a differential control pin pair can indicate that the AT86RF231 is currently in transmit mode.
The control of an external RF front-end is done via digital control pins DIG3/DIG4. The function
of this pin pair is enabled with register bit PA_EXT_EN (register 0x04, TRX_CTRL_1). While the
transmitter is turned off pin 1 (DIG3) is set to low level and pin 2 (DIG4) to high level. If the radio
transceiver starts to transmit, the two pins change the polarity. This differential pin pair can be
used to control PA, LNA, and RF switches.
If the AT86RF231 is not in a receive or transmit state, it is recommended to disable register bit
PA_EXT_EN (register 0x04, TRX_CTRL_1) to reduce the power consumption or avoid leakage
current of external RF switches and other building blocks, especially during SLEEP state. If register bits PA_EXT_EN = 0, output pins DIG3/DIG4 are pulled-down to analog ground.
11.5.2
External RF-Front End Control
Using an external RF front-end including a power amplifier (PA) it may be required to adjust the
setup time of the external PA relative to the internal building blocks to optimize the overall power
spectral density (PSD) mask.
Figure 11-11. TX Power Ramping Control for RF Front-Ends
0
TRX_STATE
PLL_ON
2
4
6
8
10
12
14
16
18
Length [µs]
BUSY_TX
SLP_TR
PA buffer
PA
Modulation
PA_BUF_LT
PA_LT
1 1 0 1 1 0 0 1 1
DIG3
DIG4
The start-up sequence of the individual building blocks of the internal transmitter is shown in Figure 11-11 on page 147, where transmission is actually initiated by the rising edge of pin 11
(SLP_TR). The radio transceiver state changes from PLL_ON to BUSY_TX and the PLL settles
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to the transmit frequency within 16 µs. The modulation starts 16 µs after the rising edge of
SLP_TR. During this time, the PA buffer and the internal PA are enabled.
The control of an external PA is done via differential pin pair DIG3/DIG4. DIG3 = H / DIG4 = L
indicates that the transmission starts and can be used to enable an external PA. The timing of
pins DIG3/DIG4 can be adjusted relative to the start of the frame and the activation of the internal PA buffer. This is controlled using register bits PA_BUF_LT and PA_LT. For details refer to
Section 9.2.4 “TX Power Ramping” on page 104.
11.5.3
Register Description
Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
+0x04
7
6
5
4
3
2
1
0
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
SPI_CMD_MODE
IRQ_MASK_MODE
IRQ_POLARITY
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
0
0
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
This register bit enables pin 1 (DIG3) and pin 2 (DIG4) to indicate the transmit state of the radio
transceiver.
Table 11-15. RF Front-End Control Pins
PA_EXT_EN
State
Pin
Value
0
n/a
DIG3
L
DIG4
L
DIG3
H
DIG4
L
DIG3
L
DIG4
H
(1)
1
TX_BUSY
Other
Note:
Description
External RF front-end control disabled
External RF front-end control enabled
1. It is recommended to set PA_EXT_EN = 1 only in receive or transmit states to reduce the
power consumption or avoid leakage current of external RF switches or other building blocks,
especially during SLEEP state.
• Bit 6 - IRQ_2_EXT_EN
Refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
Refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
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• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
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11.6
11.6.1
RX Frame Time Stamping
Overview
To determine the exact timing of an incoming frame, e.g. for beaconing networks, the reception
of this frame can be signaled to the microcontroller via pin 10 (DIG2). The pin turns from L to H
after a detection of a valid PHR. When enabled, DIG2 is set to DIG2 = H at the same time as
IRQ_2 (RX_START), even if IRQ_2 is disabled. The pin remains high for the length of the frame
receive procedure, see Figure 11-3 on page 130.
Figure 11-12. Timing of RX_START and DIG2 for RX Frame Time Stamping
Number of Octets
Frame Content
TRX_STATE
128
160
192
192 + m * 32
4
1
1
m < 128
Preamble
SFD
PHR
PSDU (250 kb/s)
RX_ON
BUSY_RX
Time [µs]
Frame
on Air
0
RX_ON
IRQ
RX
DIG2 (RX Frame Time Stamp)
IRQ_2 (RX_START)
Interrupt latency
TRX_END
tIRQ
Note:
tIRQ
Timing figures refer to 12.4 “Digital Interface Timing Characteristics” on page 157.
This function is enabled with register bit IRQ_2_EXT_EN (register 0x04) set. Pin 10 (DIG2)
could be connected to a timer capture unit of the microcontroller.
If this pin is not used for RX Frame Time Stamping it can be configured for Antenna Diversity.
Otherwise this pin is pulled-down to digital ground.
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11.6.2
Register Description
Register 0x04 (TRX_CTRL_1):
Register 0x04 (TRX_CTRL_1) is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
Reset Value
0
0
1
+0x04
3
2
1
0
SPI_CMD_MODE
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
R/W
0
0
0
0
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
If this register bit is set the RX Frame Time Stamping Mode is enabled. An incoming frame with
a valid PHR is signaled via pin 10 (DIG2). The pin remains at high level until the end of the frame
receive procedure, see Figure 11-12 on page 150.
Do not enable RX Frame Time Stamping (IRQ_2_EXT_EN = 1) and Antenna Diversity
(ANT_EXT_SW_EN = 1) at the same time, see Section 11.4 “Antenna Diversity” on page 142.
• Bit 5 - TX_AUTO_CRC_ON
Refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
Refer to Section 11.7 “Frame Buffer Empty Indicator” on page 152.
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
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11.7
11.7.1
Frame Buffer Empty Indicator
Overview
For time critical applications that want to start reading the frame data as early as possible, the
Frame Buffer status can be indicated to the microcontroller through a dedicated pin. This pin
indicates to the microcontroller if an access to the Frame Buffer is not possible since valid PSDU
data are missing.
Pin 24 (IRQ) can be configured as a Frame Buffer Empty Indicator during a Frame Buffer read
access. This mode is enabled by register bit RX_BL_CTRL (register 0x04, TRX_CTRL_1). The
IRQ pin turns into Frame Buffer Empty Indicator after the Frame Buffer read access command,
see note (1) in Figure 11-13 on page 152, has been transferred on the SPI bus until the Frame
Buffer read procedure has finished indicated by /SEL = H, see note (4).
Figure 11-13. Timing Diagram of Frame Buffer Empty Indicator
/SEL
SCLK
MOSI
MISO
IRQ
Command
XX
Command
PHY_STATUS IRQ_STATUS
PHY_STATUS
XX
PHR[7:0]
XX
XX
PSDU[7:0]
PSDU[7:0]
XX
PSDU[7:0]
XX
Command
LQI[7:0]
XX
PHY_STATUS IRQ_STATUS
Frame Buffer Empty Indicator
IRQ_2 (RX_START)
IRQ_3 (TRX_END)
t13
Notes
(1)
(2)
(3)
(4)
The microcontroller has to observe the IRQ pin during the Frame Buffer read procedure. A
Frame Buffer read access can proceed as long as pin IRQ = L, see note (2). Pin IRQ = H indicates that the Frame Buffer is currently not ready for another SPI cycle, note (3), and thus the
Frame Buffer read procedure has to wait for valid data accordingly.
The access indicator pin 24 (IRQ) shows a valid access signal (either access is allowed or
denied) not before t13 = 750 nsec after the rising edge of last SCLK clock of the Frame Buffer
read command byte.
After finishing the SPI frame receive procedure, and the SPI has been released by /SEL = H,
note (4), pending interrupts are indicated immediately by pin IRQ. During all other SPI accesses,
except during a SPI frame receive procedure with RX_BL_CTRL = 1, pin IRQ only indicates
interrupts.
If a receive error occurs during the Frame Buffer read access the Frame Buffer Empty Indicator
locks on 'empty' (pin IRQ = H) too. To prevent possible deadlocks, the microcontroller should
impose a timeout counter that checks whether the Frame Buffer Empty Indicator remains logic
high for more than 64 µs. Presuming a PHY data rate of 250 kb/s a new byte must have been
arrived at the Frame Buffer during that period. If not, the Frame Buffer read access should be
aborted.
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11.7.2
Register Description
Register 0x04 (TRX_CTRL_1):
The TRX_CTRL_1 register is a multi purpose register to control various operating modes and
settings of the radio transceiver.
Bit
7
6
5
4
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
Read/Write
R/W
R/W
R/W
Reset Value
0
0
1
+0x04
3
2
1
0
SPI_CMD_MODE
IRQ_MASK_MODE
IRQ_POLARITY
R/W
R/W
R/W
R/W
0
0
0
0
TRX_CTRL_1
• Bit 7 - PA_EXT_EN
Refer to Section 11.5 “RX/TX Indicator” on page 147.
• Bit 6 - IRQ_2_EXT_EN
Refer to Section 11.6 “RX Frame Time Stamping” on page 150.
• Bit 5 - TX_AUTO_CRC_ON
Refer to Section 8.2 “Frame Check Sequence (FCS)” on page 85.
• Bit 4 - RX_BL_CTRL
If this register bit is set the Frame Buffer Empty Indicator is enabled. After sending a Frame Buffer read command, refer to Section 6.2 “SPI Protocol” on page 19, pin 24 (IRQ) indicates to the
microcontroller that an access to the Frame Buffer is not possible since valid PSDU data are
missing.
Pin IRQ does not indicate any interrupts during this time.
Table 11-16. Frame Buffer Empty Indicator
Register Bit
RX_BL_CTRL
Value
Description
0
Frame Buffer Empty Indicator disabled
1
Frame Buffer Empty Indicator enabled
• Bit [3:2] - SPI_CMD_MODE
Refer to Section 6.3 “Radio Transceiver Status information” on page 24.
• Bit 1 - IRQ_MASK_MODE
Refer to Section 6.6 “Interrupt Logic” on page 29.
• Bit 0 - IRQ_POLARITY
Refer to Section 6.6 “Interrupt Logic” on page 29.
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11.8
Dynamic Frame Buffer Protection
11.8.1
Overview
The AT86RF231 continues the reception of incoming frames as long as it is in any receive state.
When a frame was successfully received and stored into the Frame Buffer, the following frame
will overwrite the Frame Buffer content again.
To relax the timing requirements for a Frame Buffer read access the Dynamic Frame Buffer Protection prevents that a new valid frame passes to the Frame Buffer until a Frame Buffer read
access has ended (indicated by /SEL = H, refer to Section 6.2 “SPI Protocol” on page 19).
A received frame is automatically protected against overwriting:
• in Basic Operating Mode, if its FCS is valid
• in Extended Operating Mode, if an IRQ_3 (TRX_END) is generated
The Dynamic Frame Buffer Protection is enabled, if register bit RX_SAFE_MODE (register
0x0C, TRX_CTRL_2) is set and the transceiver state is RX_ON or RX_AACK_ON.
Note that Dynamic Frame Buffer Protection only prevents write accesses from the air interface not from the SPI interface. A Frame Buffer or SRAM write access may still modify the Frame
Buffer content.
11.8.2
Register Description
Register 0x0C (TRX_CTRL_2):
The TRX_CTRL_2 register is a multi purpose register to control various settings of the radio
transceiver.
Bit
+0x0C
7
6
5
RX_SAFE_MODE
4
3
2
1
Reserved
0
OQPSK_DATA_RATE
TRX_CTRL_2
Read/Write
R/W
R
R
R
R
R
R/W
R/W
Reset Value
0
0
0
0
0
0
0
0
• Bit 7 - RX_SAFE_MODE
If this bit is set Dynamic Frame Buffer Protection is enabled:
Table 11-17. Dynamic Frame Buffer Protection Mode
Register Bit
RX_SAFE_MODE(1)
Note:
Value
Description
0
Disable Dynamic Frame Buffer Protection
1
Enable Dynamic Frame Buffer Protection
1. Dynamic Frame Buffer Protection is released with the rising edge of pin23 (/SEL) of a Frame
Buffer read access, see Section 6.2.2 “Frame Buffer Access Mode” on page 20, or radio transceiver state changing from RX_ON or RX_AACK_ON to another state.
This operation mode is independent of the setting of register bits RX_PDT_LEVEL, refer to Section 9.1.3 “Configuration” on page 102.
• Bit [6:2] - Reserved
• Bit [1:0] - OQPSK_DATA_RATE
Refer to Section 11.3 “High Data Rate Modes” on page 137.
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11.9
11.9.1
Configurable Start-Of-Frame Delimiter
Overview
The SFD is a field indicating the end of the SHR and the start of the packet data. The length of
the SFD is 1 octet (2 symbols). This octet is used for byte synchronization only and is not
included in the Frame Buffer.
The value of the SFD could be changed if it is needed to operate non IEEE 802.15.4 compliant
networks. An IEEE 802.15.4 compliant network node does not synchronize to frames with a different SFD value.
Due to the way the SHR is formed, it is not recommended to set the low-order 4 bits to 0. The
LSB of the SFD is transmitted first, i.e. right after the last bit of the preamble sequence.
11.9.2
Register Description
Register 0x0B (SFD_VALUE):
This register contains the one octet start-of-frame delimiter (SFD) to synchronize to a received
frame.
Bit
7
6
5
+0x0B
4
3
2
1
0
SFD_VALUE[7:0]
SFD_VALUE
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
1
0
1
0
0
1
1
1
• Bit [7:0] - SFD_VALUE
For compliant IEEE 802.15.4 networks set SFD_VALUE = 0xA7, as specified by [1] and [2]. This
is the default value of the register.
To establish non IEEE 802.15.4 compliant networks the SFD value can be changed to any other
value. If enabled an IRQ_2 (RX_START) is issued only if the received SFD matches the register
content of register SFD_VALUE and a valid PHR is received.
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12. Electrical Characteristics
12.1
Absolute Maximum Ratings
Note:
Table 12-1.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage
to the device. This is a stress rating only and functional operation of the device at these or any
other conditions beyond those indicated in the operational sections of this specification are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Absolute Maximum Ratings
No.
Symbol
Parameter
12.1.1
TSTOR
Storage temperature
12.1.2
TLEAD
Lead temperature
T = 10s,
(soldering profile compliant with
IPC/JEDEC J STD 020B)
12.1.3
VESD
ESD robustness
Compl. to [3],
Compl. to [4]
12.1.4
PRF
Input RF level
12.1.5
VDIG
Voltage on all pins
(except pins 4, 5, 13, 14, 29)
-0.3
VDD+0.3
V
12.1.6
VANA
Voltage on pins 4, 5, 13, 14, 29
-0.3
2.0
V
Max
Units
+85
°C
12.2
Condition
Min.
Typ.
-50
Max
Units
150
°C
260
°C
5000
1500
V
V
+10
dBm
Recommended Operating Range
Table 12-2.
Recommended Operating Range
No.
Symbol
Parameter
12.2.1
TOP
Operating temperature range
12.2.2
VDD
Supply voltage
Voltage on pins 15, 28(1)
1.8
3.0
3.6
V
12.2.3
VDD1.8
Supply voltage
External voltage supply on pins
13, 14, 29(2)
1.7
1.8
1.9
V
Notes:
Condition
Min.
Typ.
-40
1. Even if an implementation uses the external 1.8V voltage supply VDD1.8 it is required to connect VDD.
2. Register 0x10 (VREG_CTRL) needs to be programmed to disable internal voltage regulators and supply blocks by an external 1.8V supply, refer to “Voltage Regulators (AVREG, DVREG)” on page 110.
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12.3
Digital Pin Characteristics
.Test Conditions: TOP = 25°C (unless otherwise stated)
Table 12-3.
No.
Digital Pin Characteristics
Symbol
Parameter
Condition
(1)
12.3.1
VIH
High level input voltage
12.3.2
VIL
Low level input voltage(1)
(1)
12.3.3
VOH
High level output voltage
12.3.4
VOL
Low level output voltage(1)
Min.
Typ.
Max
VDD - 0.4
V
0.4
For all output driver strengths defined
in TRX_CTRL_0
Units
VDD - 0.4
V
V
For all output driver strengths defined
in TRX_CTRL_0
0.4
V
Note:
1. The capacitive load should not be larger than 50 pF for all I/Os when using the default driver strength settings, refer to Section 1.3.1 “Driver Strength Settings” on page 7. Generally, large load capacitances increase the overall current consumption.
12.4
Digital Interface Timing Characteristics
Test Conditions: TOP = 25°C, VDD = 3.0V, CL = 50 pF (unless otherwise stated).
Table 12-4.
No.
Digital Interface Timing Characteristics
Symbol
Parameter
Condition
Min.
Typ.
Max
Units
12.4.1
fsync
SCLK frequency
synchronous operation
8
MHz
12.4.2
fasync
SCLK frequency
asynchronous operation
7.5
MHz
12.4.3
t1
/SEL low to MISO active
180
ns
12.4.4
t2
SCLK to MISO out
12.4.5
t3
12.4.6
t4
data hold time
10
ns
MOSI setup time
10
ns
MOSI hold time
10
ns
(2)
12.4.7
t5
LSB last byte to MSB next byte
250
ns
12.4.8
t6
/SEL high to MISO tri state
12.4.9
t7
SLP_TR pulse width
TX start trigger
62.5
12.4.10
t8
SPI idle time
(SEL rising to falling edge)
SPI read/write, standard SRAM
and Frame Buffer access modes,
Idle time between consecutive SPI
accesses
250
ns
12.4.11
t8
SPI idle time
(SEL rising to falling edge)
SPI Fast SRAM read/write access
mode, refer to Section 11.1.5,
Idle time between consecutive SPI
accesses
500
ns
12.4.12
t9
Last SCLK to /SEL high
12.4.13
t10
Reset pulse width
10 clock cycles at 16 MHz
625
ns
12.4.14
t11
SPI access latency after reset
10 clock cycles at 16 MHz
625
ns
12.4.15
t12
AES core cycle time
250
24
10
ns
Note(1)
ns
ns
µs
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Table 12-4.
Digital Interface Timing Characteristics (Continued)
12.4.15
t13
BFBP IRQ latency
12.4.17
tIRQ
Interrupt event latency
Relative to the event to be indicated
12.4.18
fCLKM
Clock frequency at pin 17 (CLKM)
Configurable in register 0x03
(TRX_CTRL_0)
Notes:
750
ns
9
µs
0
1
2
4
8
16
250
62.5
MHz
MHz
MHz
MHz
MHz
MHz
kHz
kHz
1. Maximum pulse width less than (TX frame length + 16 µs)
2. For Fast SRAM read/write accesses on address space 0x82 - 0x94 the time t5 (Min.) increases to 450 ns.
12.5
General RF Specifications
Test Conditions (unless otherwise stated):
VDD = 3.0V, fRF = 2.45 GHz, TOP = 25°C, Measurement setup see Figure 5-1 on page 12.
Table 12-5.
General RF Specifications
No.
Symbol
Parameter
Condition
Min.
12.5.1
fRF
Frequency range
As specified in [1], [2]
2405
12.5.2
fCH
Channel spacing
As specified in [1], [2]
5
MHz
12.5.3
fHDR
Header bit rate (SHR, PHR)
As specified in [1], [2]
250
kb/s
12.5.4
fPSDU
PSDU bit rate
As specified in [1], [2]
OQPSK_DATA_RATE = 1
OQPSK_DATA_RATE = 2
OQPSK_DATA_RATE = 3
250
500
1000
2000
kb/s
kb/s
kb/s
kb/s
12.5.5
fCHIP
Chip rate
As specified in [1], [2]
2000
kchip/s
12.5.6
fCLK
Crystal oscillator frequency
Reference oscillator
16
12.5.7
tXTAL
Reference oscillator settling time
Leaving SLEEP state to clock
available at pin 17 (CLKM)
330
Symbol rate deviation
Reference frequency accuracy for
correct functionality
PSDU bit rate 250 kb/s
PSDU bit rate 500 kb/s
PSDU bit rate 1000 kb/s
PSDU bit rate 2000 kb/s
12.5.8
12.5.9
Note:
B20dB
20 dB bandwidth
Typ.
-60(1)
-40
-40
-30
2.8
Max
Units
2480
MHz
MHz
1000
µs
+60
+40
+40
+30
ppm
ppm
ppm
ppm
MHz
1. A reference frequency accuracy of ±40 ppm is required by [1], [2].
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12.6
Transmitter Characteristics
Test Conditions (unless otherwise stated):
VDD = 3.0V, fRF = 2.45 GHz, TOP = 25°C, Measurement setup see Figure 5-1 on page 12.
Table 12-6.
Transmitter Characteristics
No.
Symbol
Parameter
Condition
12.6.1
PTX
TX Output power
Maximum configurable TX output
power value
Register bit TX_PWR = 0
12.6.2
PRANGE
Output power range
16 steps, configurable in
register 0x05 (PHY_TX_PWR)
12.6.3
PACC
Output power tolerance
12.6.4
TX Return loss
12.6.5
EVM
12.6.6
12.6.7
PHARM
PSPUR
Typ.
Max
Units
0
+3
+6
dBm
20
dB
±3
100Ω differential impedance,
PTX = +3 dBm
Harmonics
2nd harmonic
3rd harmonic
Spurious Emissions
30 - ≤ 1000 MHz
>1 - 12.75 GHz
1.8 - 1.9 GHz
5.15 - 5.3 GHz
Min.
10
dB
8
%rms
-45
dBm
dBm
-36
-30
-47
-47
dBm
dBm
dBm
dBm
-45
Complies with
EN 300 328/440,
FCC-CFR-47 part 15,
ARIB STD-66, RSS-210
dB
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12.7
Receiver Characteristics
Test Conditions (unless otherwise stated):
VDD = 3.0V, fRF = 2.45 GHz, TOP = 25°C, PSDU bit rate = 250 kb/s, Measurement setup see Figure 5-1 on page 12.
Table 12-7.
Receiver Characteristics
No.
Symbol
Parameter
Condition
12.7.1
PSENS
Receiver sensitivity
250 kb/s
500 kb/s
1000 kb/s
2000 kb/s
AWGN channel, PER ≤ 1%,
PSDU length 20 octets
High Data Rate Modes:
PSDU length 20 octets
Antenna Diversity
Min.
Typ.
Max
Units
-101
-97
-95
-89
dBm
dBm
dBm
dBm
250 kb/s, PSDU 20 octets
-99
dBm
100Ω differential impedance
10
dB
6
dB
12.7.2
RL
Return loss
12.7.3
NF
Noise figure
12.7.4
PRXMX
Maximum RX input level
PER ≤ 1%, PSDU length of 20 octets
10
dBm
12.7.5
PACRN
Adjacent channel rejection:
Δf = -5 MHz
PER ≤ 1%, PSDU length of 20 octets,
PRF = -82 dBm
32
dB
12.7.6
PACRP
Adjacent channel rejection:
Δf = +5 MHz
PER ≤ 1%, PSDU length of 20 octets,
PRF = -82 dBm
35
dB
12.7.7
PAACR1
Alternate channel rejection:
Δf = |10 MHz|
PER ≤ 1%, PSDU length of 20 octets,
PRF = -82 dBm
48
dB
12.7.8
PAACR2
2nd Alternate channel rejection:
Δf = |15 MHz|
PER ≤ 1%, PSDU length of 20 octets,
PRF = -82 dBm
54
dB
12.7.9
PSPUR
Spurious emissions:
LO leakage
30 - ≤1000 MHz
>1 - 12.75 GHz
12.7.10
fRXTXOFFS
TX/RX carrier frequency offset
rd
-70
Sensitivity loss < 2 dB
-300(1)
-57
-47
dBm
dBm
dBm
+300
kHz
12.7.11
IIP3
3 - order intercept point
At maximum gain
Offset freq. interf. 1 = 5 MHz
Offset freq. interf. 2 = 10 MHz
-10
dBm
12.7.12
IIP2
2nd - order intercept point
At maximum gain
Offset freq. interf. 1 = 60 MHz
Offset freq. interf. 2 = 62 MHz
31
dBm
12.7.13
RSSI tolerance
Tolerance within gain step
12.7.14
RSSI dynamic range
81
dB
12.7.15
RSSI resolution
3
dB
12.7.16
RSSI sensitivity
Defined as RSSI_BASE_VAL
12.7.17
Minimum RSSI value
PRF ≤ RSSI_BASE_VAL
0
12.7.18
Maximum RSSI value
PRF > RSSI_BASE_VAL + 81 dB
28
Note:
±5
-91
dB
dBm
1. Offset equals ±120 ppm.
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12.8
Current Consumption Specifications
Test Conditions (unless otherwise stated):
VDD = 3.0V, fRF = 2.45 GHz, TOP = 25°C, Measurement setup see Figure 5-1 on page 12.
Table 12-8.
Current Consumption Specifications(1)
No.
Symbol
Parameter
Condition
12.8.1
IBUSY_TX
Supply current transmit state
PTX = 3 dBm
PTX = 0 dBm
PTX = -17 dBm
14
11.6
7.4
mA
mA
mA
12.8.2
IRX_ON
Supply current RX_ON state
RX_ON state - high input level
10.3
mA
12.8.3
IRX_ON
Supply current RX_ON state
RX_ON state - high sensitivity
12.3
mA
12.8.4
IPLL_ON_P
Supply current RX_ON state
RX_ON state, with register setting
RX_PDT_LEVEL > 0(2)
11.8
mA
12.8.5
IPLL_ON
Supply current PLL_ON state
PLL_ON state
5.6
mA
12.8.6
ITRX_OFF
Supply current TRX_OFF state
TRX_OFF state
0.4
mA
12.8.7
ISLEEP
Supply current SLEEP state
SLEEP state
Note:
Min.
Typ.
Max
Units
0.02
µA
Max
Units
1. Current consumption for all operating modes is reduced at lower VDD.
2. Refer to Section 9.1 “Receiver (RX)” on page 101
12.9
Crystal Parameter Requirements
Table 12-9.
Crystal Parameter Requirements
No.
Symbol
Parameter
12.9.1
f0
Crystal frequency
12.9.2
CL
Load capacitance
12.9.3
C0
12.9.4
R1
Condition
Min.
Typ.
16
8
MHz
14
pF
Static capacitance
7
pF
Series resistance
100
Ω
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AT86RF231
13. Typical Characteristics
13.1
Active Supply Current
The following charts showing each a typical behavior of the AT86RF231. These figures are not
tested during manufacturing. All power consumption measurements are performed with pin 17
(CLKM) disabled, unless otherwise stated. The measurement setup used for the measurements
is shown in Figure 5-1 on page 12.
Power consumption for the microcontroller required to program the radio transceiver is not
included in the measurement results.
The power consumption in SLEEP state mode is independent from CLKM master clock rate
selection.
The current consumption is a function of several factors such as: operating voltage, operating
frequency, loading of I/O pins, switching rate of I/O pins, and ambient temperature. The dominating factors are operating voltage and ambient temperature.
If possible the measurement results are not affected by current drawn from I/O pins. Register,
SRAM or Frame Buffer read or write accesses are not performed during current consumption
measurements.
13.1.1
P_ON and TRX_OFF states
Figure 13-1. Current Consumption in P_ON State
Current Consumption [mA]
0.7
85 °C
25 °C
0 °C
-40 °C
0.6
0.5
0.4
0.3
0.2
0.1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
162
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AT86RF231
Figure 13-2. Current Consumption in TRX_OFF State
Current Consumption [mA]
0.5
85 °C
25 °C
0 °C
-40 °C
0.4
0.3
0.2
0.1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
13.1.2
PLL_ON state
Figure 13-3. Current Consumption in PLL_ON State
Current Consumption [mA]
7
85 °C
25 °C
0 °C
-40 °C
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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AT86RF231
13.1.3
RX_ON state
Figure 13-4. Current Consumption in RX_ON State - High Sensitivity
15
Current Consumption [mA]
14
85 °C
25 °C
0 °C
-40 °C
13
12
11
10
9
8
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 13-5. Current Consumption in RX_ON State - High Input Level
15
Current Consumption [mA]
14
13
85 °C
25 °C
0 °C
-40 °C
12
11
10
9
8
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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AT86RF231
Figure 13-6. Current Consumption in RX_ON State - Reduced Sensitivity
15
Current Consumption [mA]
14
85 °C
13
25 °C
0 °C
-40 °C
12
11
10
9
8
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
13.1.4
TX_BUSY state
Figure 13-7. Current Consumption in TX_BUSY State - Minimum Output Power
Current Consumption [mA]
14
12
10
85 °C
25 °C
0 °C
-40 °C
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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AT86RF231
Figure 13-8. Current Consumption in TX_BUSY State - Output Power 0 dBm
16
Current Consumption [mA]
14
85 °C
25 °C
0 °C
-40 °C
12
10
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 13-9. Current Consumption in TX_BUSY State - Maximum Output Power
16
85 °C
25 °C
0 °C
-40 °C
Current Consumption [mA]
14
12
10
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
166
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AT86RF231
13.1.5
SLEEP
Figure 13-10. Current Consumption in SLEEP
1000
Current Consumption [nA]
85 °C
100
25 °C
10
-40 °C
1
0.1
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
13.2
State Transition Timing
Figure 13-11. Transition Time from EVDD to P_ON (CLKM available)
500
450
Setting Time [ms]
400
85 °C
25 °C
0 °C
-40 °C
350
300
250
200
150
100
50
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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Figure 13-12. Transition Time from SLEEP to TRX_OFF (IRQ_4 (AWAKE_END))
500
450
85 °C
25 °C
0 °C
-40 °C
Setting Time [ms]
400
350
300
250
200
150
100
50
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 13-13. Transition Time from TRX_OFF to PLL_ON
140
85 °C
25 °C
0 °C
-40 °C
State Transition Time [µs]
120
100
80
60
40
20
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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14. Register Summary
The AT86RF231 provides a register space of 64 8-bit registers, used to configure, control and
monitor the radio transceiver.
Note:
All registers not mentioned within the following table are reserved for internal use and must not be
overwritten. When writing to a register, any reserved bits shall be overwritten only with their reset
value.
Addr
Name
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
0x00
-
-
-
-
-
-
-
-
-
Page
-
0x01
TRX_STATUS
CCA_DONE
CCA_STATUS
-
TRX_STATUS[4]
TRX_STATUS[3]
TRX_STATUS[2]
TRX_STATUS[1]
TRX_STATUS[0]
44,68,97
33,44,68
0x02
TRX_STATE
TRAC_STATUS[2]
TRAC_STATUS[1]
TRAC_STATUS[0]
TRX_CMD[4]
TRX_CMD[3]
TRX_CMD[2]
TRX_CMD[1]
TRX_CMD[0]
0x03
TRX_CTRL_0
PAD_IO[1]
PAD_IO[0]
PAD_IO_CLKM[1]
PAD_IO_CLKM[0]
CLKM_SHA_SEL
CLKM_CTRL[2]
CLKM_CTRL[1]
CLKM_CTRL[0]
8,118,
0x04
TRX_CTRL_1
PA_EXT_EN
IRQ_2_EXT_EN
TX_AUTO_CRC_ON
RX_BL_CTRL
SPI_CMD_MODE[1]
SPI_CMD_MODE[0]
IRQ_MASK_MODE
IRQ_POLARITY
24,30,148
0x05
PHY_TX_PWR
PA_BUF_LT[1]
PA_BUF_LT[0]
PA_LT[1]
PA_LT[0]
TX_PWR[3]
TX_PWR[2]
TX_PWR[1]
TX_PWR[0]
105
0x06
PHY_RSSI
RX_CRC_VALID
RND_VALUE[1]
RND_VALUE[0]
RSSI[4]
RSSI[3]
RSSI[2]
RSSI[1]
RSSI[0]
90,136
0x07
PHY_ED_LEVEL
ED_LEVEL[7]
ED_LEVEL[6]
ED_LEVEL[5]
ED_LEVEL[4]
ED_LEVEL[3]
ED_LEVEL[2]
ED_LEVEL[1]
ED_LEVEL[0]
93
0x08
PHY_CC_CCA
CCA_REQUEST
CCA_MODE[1]
CCA_MODE[0]
CHANNEL[4]
CHANNEL[3]
CHANNEL[2]
CHANNEL[1]
CHANNEL[0]
97
0x09
CCA_THRES
-
-
-
-
CCA_ED_THRES[3]
CCA_ED_THRES[2]
CCA_ED_THRES[1]
CCA_ED_THRES[0]
97
0x0A
RX_CTRL
-
-
-
-
PDT_THRES[3]
PDT_THRES[2]
PDT_THRES[1]
PDT_THRES[0]
140
0x0B
SFD_VALUE
SFD_VALUE[7]
SFD_VALUE[6]
SFD_VALUE[5]
SFD_VALUE[4]
SFD_VALUE[3]
SFD_VALUE[2]
SFD_VALUE[1]
SFD_VALUE[0]
155
0x0C
TRX_CTRL_2
RX_SAFE_MODE
-
-
-
-
-
OQPSK_DATA_RATE[1]
OQPSK_DATA_RATE[0]
154
0x0D
ANT_DIV
ANT_SEL
-
-
-
ANT_DIV_EN
ANT_EXT_SW_EN
ANT_CTRL[1]
ANT_CTRL[0]
143
0x0E
IRQ_MASK
MASK_BAT_LOW
MASK_TRX_UR
MASK_AMI
MASK_CCA_ED_DONE
MASK_TRX_END
MASK_TRX_START
MASK_PLL_UNLOCK
MASK_PLL_LOCK
30
0x0F
IRQ_STATUS
BAT_LOW
TRX_UR
AMI
CCA_ED_DONE
TRX_END
RX_START
PLL_UNLOCK
PLL_LOCK
30
0x10
VREG_CTRL
AVREG_EXT
AVDD_OK
-
-
DVREG_EXT
DVDD_OK
-
-
111
0x11
BATMON
-
-
BATMON_OK
BATMON_HR
BATMON_VTH[3]
BATMON_VTH[2]
BATMON_VTH[1]
BATMON_VTH[0]
113
0x12
XOSC_CTRL
XTAL_MODE[3]
XTAL_MODE[2]
XTAL_MODE[1]
XTAL_MODE[0]
XTAL_TRIM[3]
XTAL_TRIM[2]
XTAL_TRIM[1]
XTAL_TRIM[0]
116
0x13
-
-
-
-
-
-
-
-
-
0x14
-
-
-
-
-
-
-
-
-
0x15
RX_SYN
RX_PDT_DIS
-
-
-
RX_PDT_LEVEL[3]
RX_PDT_LEVEL[2]
RX_PDT_LEVEL[1]
RX_PDT_LEVEL[0]
0x16
-
-
-
-
-
-
-
-
-
0x17
XAH_CTRL_1
-
-
AACK_FLTR_RES_FT
AACK_UPLD_RES_FT
-
AACK_ACK_TIME
AACK_PROM_MODE
-
68,140
0x18
FTN_CTRL
FTN_START
-
-
-
-
-
-
-
125
0x19
-
-
-
-
-
-
-
-
-
103
0x1A
PLL_CF
PLL_CF_START
-
-
-
-
-
-
-
122
0x1B
PLL_DCU
PLL_DCU_START
-
-
-
-
-
-
-
122
0x1C
PART_NUM
PART_NUM[7]
PART_NUM[6]
PART_NUM[5]
PART_NUM[4]
PART_NUM[3]
PART_NUM[2]
PART_NUM[1]
PART_NUM[0]
25
0x1D
VERSION_NUM
VERSION_NUM[7]
VERSION_NUM[6]
VERSION_NUM[5]
VERSION_NUM[4]
VERSION_NUM[3]
VERSION_NUM[2]
VERSION_NUM[1]
VERSION_NUM[0]
25
0x1E
MAN_ID_0
MAN_ID_0[7]
MAN_ID_0[6]
MAN_ID_0[5]
MAN_ID_0[4]
MAN_ID_0[3]
MAN_ID_0[2]
MAN_ID_0[1]
MAN_ID_0[0]
25
0x1F
MAN_ID_1
MAN_ID_1[7]
MAN_ID_1[6]
MAN_ID_1[5]
MAN_ID_1[4]
MAN_ID_1[3]
MAN_ID_1[2]
MAN_ID_1[1]
MAN_ID_1[0]
25
0x20
SHORT_ADDR_0
SHORT_ADDR_0[7]
SHORT_ADDR_0[6]
SHORT_ADDR_0[5]
SHORT_ADDR_0[4]
SHORT_ADDR_0[3]
SHORT_ADDR_0[2]
SHORT_ADDR_0[1]
SHORT_ADDR_0[0]
76
0x21
SHORT_ADDR_1
SHORT_ADDR_1[7]
SHORT_ADDR_1[6]
SHORT_ADDR_1[5]
SHORT_ADDR_1[4]
SHORT_ADDR_1[3]
SHORT_ADDR_1[2]
SHORT_ADDR_1[1]
SHORT_ADDR_1[0]
76
0x22
PAN_ID_0
PAN_ID_0[7]
PAN_ID_0[6]
PAN_ID_0[5]
PAN_ID_0[4]
PAN_ID_0[3]
PAN_ID_0[2]
PAN_ID_0[1]
PAN_ID_0[0]
76
0x23
PAN_ID_1
PAN_ID_1[7]
PAN_ID_1[6]
PAN_ID_1[5]
PAN_ID_1[4]
PAN_ID_1[3]
PAN_ID_1[2]
PAN_ID_1[1]
PAN_ID_1[0]
76
0x24
IEEE_ADDR_0
IEEE_ADDR_0[7]
IEEE_ADDR_0[6]
IEEE_ADDR_0[5]
IEEE_ADDR_0[4]
IEEE_ADDR_0[3]
IEEE_ADDR_0[2]
IEEE_ADDR_0[1]
IEEE_ADDR_0[0]
76
0x25
IEEE_ADDR_1
IEEE_ADDR_1[7]
IEEE_ADDR_1[6]
IEEE_ADDR_1[5]
IEEE_ADDR_1[4]
IEEE_ADDR_1[3]
IEEE_ADDR_1[2]
IEEE_ADDR_1[1]
IEEE_ADDR_1[0]
76
0x26
IEEE_ADDR_2
IEEE_ADDR_2[7]
IEEE_ADDR_2[6]
IEEE_ADDR_2[5]
IEEE_ADDR_2[4]
IEEE_ADDR_2[3]
IEEE_ADDR_2[2]
IEEE_ADDR_2[1]
IEEE_ADDR_2[0]
76
0x27
IEEE_ADDR_3
IEEE_ADDR_3[7]
IEEE_ADDR_3[6]
IEEE_ADDR_3[5]
IEEE_ADDR_3[4]
IEEE_ADDR_3[3]
IEEE_ADDR_3[2]
IEEE_ADDR_3[1]
IEEE_ADDR_3[0]
76
0x28
IEEE_ADDR_4
IEEE_ADDR_4[7]
IEEE_ADDR_4[6]
IEEE_ADDR_4[5]
IEEE_ADDR_4[4]
IEEE_ADDR_4[3]
IEEE_ADDR_4[2]
IEEE_ADDR_4[1]
IEEE_ADDR_4[0]
76
0x29
IEEE_ADDR_5
IEEE_ADDR_5[7]
IEEE_ADDR_5[6]
IEEE_ADDR_5[5]
IEEE_ADDR_5[4]
IEEE_ADDR_5[3]
IEEE_ADDR_5[2]
IEEE_ADDR_5[1]
IEEE_ADDR_5[0]
76
0x2A
IEEE_ADDR_6
IEEE_ADDR_6[7]
IEEE_ADDR_6[6]
IEEE_ADDR_6[5]
IEEE_ADDR_6[4]
IEEE_ADDR_6[3]
IEEE_ADDR_6[2]
IEEE_ADDR_6[1]
IEEE_ADDR_6[0]
76
0x2B
IEEE_ADDR_7
IEEE_ADDR_7[7]
IEEE_ADDR_7[6]
IEEE_ADDR_7[5]
IEEE_ADDR_7[4]
IEEE_ADDR_7[3]
IEEE_ADDR_7[2]
IEEE_ADDR_7[1]
IEEE_ADDR_7[0]
76
0x2C
XAH_CTRL_0
MAX_FRAME_RETRES[3]
MAX_FRAME_RETRES[2]
MAX_FRAME_RETRES[1]
MAX_FRAME_RETRES[0]
MAX_CSMA_RETRES[2]
MAX_CSMA_RETRES[1]
MAX_CSMA_RETRES[0]
SLOTTED_OPERATION
68
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0x2D
CSMA_SEED_0
CSMA_SEED_0[7]
CSMA_SEED_0[6]
CSMA_SEED_0[5]
CSMA_SEED_0[4]
CSMA_SEED_0[3]
CSMA_SEED_0[2]
CSMA_SEED_0[1]
CSMA_SEED_0[0]
68
0x2E
CSMA_SEED_1
AACK_FVN_MODE[1]
AACK_FVN_MODE[0]
AACK_SET_PD
AACK_DIS_ACK
AACK_I_AM_COORD
CSMA_SEED_1[2]
CSMA_SEED_1[1]
CSMA_SEED_1[0]
68
0x2F
CSMA_BE
MAX_BE[3]
MAX_BE[2]
MAX_BE[1]
MAX_BE[0]
MIN_BE[3]
MIN_BE[2]
MIN_BE[1]
MIN_BE[0]
68
....
-
-
-
-
-
-
-
-
-
The reset values of the AT86RF231 registers in state P_ON(1, 2, 3) are shown in Table 14-1 on
page 170.
Note:
Table 14-1.
All reset values in Table 14-1 on page 170 are only valid after a power on reset. After a reset procedure (/RST = L) as described in Section 7.1.4.5 “Reset Procedure” on page 41 the reset values
of selected registers (e.g. registers 0x01, 0x10, 0x11, 0x30) can differ from that in Table 14-1 on
page 170.
Register Summary - Reset Values
Address
Reset Value
Address
Reset Value
Address
Reset Value
Address
Reset Value
0x00
0x00
0x10
0x00(1)
0x20
0xFF
0x30
0x00(3)
0x01
0x00
0x11
0x02(2)
0x21
0xFF
0x31
0x00
0x02
0x00
0x12
0xF0
0x22
0xFF
0x32
0x00
0x03
0x19
0x13
0x00
0x23
0xFF
0x34
0x00
0x04
0x20
0x14
0x00
0x24
0x00
0x34
0x00
0x05
0xC0
0x15
0x00
0x25
0x00
0x35
0x00
0x06
0x00
0x16
0x00
0x26
0x00
0x36
0x00
0x07
0xFF
0x17
0x00
0x27
0x00
0x37
0x00
0x08
0x2B
0x18
0x58
0x28
0x00
0x38
0x00
0x09
0xC7
0x19
0x55
0x29
0x00
0x39
0x40
0x0A
0xB7
0x1A
0x57
0x2A
0x00
0x3A
0x00
0x0B
0xA7
0x1B
0x20
0x2B
0x00
0x3B
0x00
0x0C
0x00
0x1C
0x03
0x2C
0x38
0x3C
0x00
0x0D
0x03
0x1D
0x02
0x2D
0xEA
0x3D
0x00
0x0E
0x00
0x1E
0x1F
0x2E
0x42
0x3E
0x00
0x0F
0x00
0x1F
0x00
0x2F
0x53
0x3F
0x00
Notes:
1. While the reset value of register 0x10 is 0x00, any practical access to the register is only possible when DVREG is active. So
this register is normally always read out as 0x04. For details refer to Section 9.4 “Voltage Regulators (AVREG, DVREG)” on
page 110.
2. While the reset value of register 0x11 is 0x02, any practical access to the register is only possible when BATMON is activated. So this register is normally always read out as 0x22 in P_ON state. For details refer to Section 9.5 “Battery Monitor
(BATMON)” on page 113.
3. While the reset value of register 0x30 is 0x00, any practical access to the register is only possible when the radio transceiver
is accessible. So the register is normally read out as:
a) 0x11 after a reset in P_ON state
b) 0x07 after a reset in any other state
170
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AT86RF231
15. Abbreviations
AACK
-
Automatic acknowledgement
ACK
-
Acknowledgement
ADC
-
Analog-to-digital converter
AD
-
Antenna diversity
AGC
-
Automated gain control
AES
-
Advanced encryption standard
ARET
-
Automatic retransmission
AVREG
-
Voltage regulator for analog building blocks
AWGN
-
Additive White Gaussian Noise
BATMON
-
Battery monitor
BBP
-
Base band processor
BPF
-
Band pass filter
CBC
-
Cipher block chaining
CRC
-
Cyclic redundancy check
CCA
-
Clear channel assessment
CSMA-CA
-
Carrier sense multiple access/Collision avoidance
CW
-
Continuous wave
DFBP
-
Dynamic Frame Buffer Protection
DVREG
-
Voltage regulator for digital building blocks
ECB
-
Electronic code book
ED
-
Energy detection
ESD
-
Electrostatic discharge
EVM
-
Error vector magnitude
FCF
-
Frame control field
FCS
-
Frame check sequence
FIFO
-
First in first out
FTN
-
Filter tuning network
GPIO
-
General purpose input output
ISM
-
Industrial, scientific, and medical
LDO
-
Low-drop output
LNA
-
Low-noise amplifier
LO
-
Local oscillator
LQI
-
Link quality indicator
LSB
-
Least significant bit
MAC
-
Medium access control
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MFR
-
MAC footer
MHR
-
MAC header
MISO
-
SPI Interface: Master input slave output
MOSI
-
SPI Interface: Master output slave input
MSB
-
Most significant bit
MSDU
-
MAC service data unit
MPDU
-
MAC protocol data unit
MSK
-
Minimum shift keying
O-QPSK
-
Offset - quadrature phase shift keying
PA
-
Power amplifier
PAN
-
Personal area network
PCB
-
Printed circuit board
PER
-
Packet error rate
PHR
-
PHY header
PHY
-
Physical layer
PLL
-
Phase locked loop
POR
-
Power-on reset
PPF
-
Poly-phase filter
PRBS
-
Pseudo random bit sequence
PSDU
-
PHY service data unit
PSD
-
Power spectral mask
QFN
-
Quad flat no-lead package
RF
-
Radio frequency
RSSI
-
Received signal strength indicator
RX
-
Receiver
SCLK
-
SPI Interface: SPI clock
/SEL
-
SPI Interface: SPI select
SFD
-
Start-of-frame delimiter
SHR
-
Synchronization header
SPI
-
Serial peripheral interface
SRAM
-
Static random access memory
SSBF
-
Single side band filter
TX
-
Transmitter
VCO
-
Voltage controlled oscillator
VREG
-
Voltage regulator
XOSC
-
Crystal oscillator
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16. Ordering Information
Ordering Code
Package
Voltage Range
Temperature Range
AT86RF231-ZU
QN
1.8V - 3.6V
Industrial (-40° C to +85° C) Lead-free/Halogen-free
AT86RF231-ZF
QN
1.8V - 3.6V
Industrial (-40° C to +125° C) Lead-free/Halogen-free
Package Type
Description
QN
32QN2, 32 lead 5.0x5.0 mm Body, 0.50 mm Pitch, Quad Flat No-lead Package (QFN) Sawn
Note:
T&R quantity 4,000.
Please contact your local Atmel sales office for more detailed ordering information and
minimum quantities.
17. Soldering Information
Recommended soldering profile is specified in IPC/JEDEC J-STD-.020C.
18. Package Thermal Properties
Thermal Resistance
Velocity [m/s]
Theta ja [K/W]
0
40.9
1
35.7
2.5
32.0
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19. Package Drawing - 32QN2
D
A
A3
E
Pin 1 Corner
A1
A2
Top View
Side View
Pin 1 Corner
COMMON DIMENSIONS
(Unit of Measure = mm)
SYMBOL
D2
MIN
D
E
e
E2
L
3.30
3.40
E2
3.20
3.30
3.40
A
0.80
0.90
1.00
A1
0.0
0.02
0.05
A2
0.0
0.65
1.00
L
Notes:
b
NOTE
5.00 BSC
3.20
0.20 REF
0.30
e
Bottom View
MAX
D2
A3
b
NOM
5.00 BSC
0.40
0.50
0.50 BSC
0.18
0.23
0.30
2
1. This drawing is for general information only. Refer to JEDEC Drawing MO-220, Variation VHHD-6, for proper dimensions,
tolerances, datums, etc.
2. Dimension b applies to metallized terminal and is measured between 0.15 mm and 0.30 mm from the terminal tip. If the
terminal has the optional radius on the other end of the terminal, the dimension should not be measured in that radius area.
GPC
TITLE
32QN2, 32-lead 5.0 x 5.0 mm Body, 0.50 mm Pitch,
Package Drawing Contact:
ZJZ
[email protected] Quad Flat No Lead Package (QFN) Sawn
11/26/07
DRAWING NO. REV.
32QN2
A
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20. Appendix A - Continuous Transmission Test Mode
20.1
Overview
The AT86RF231 offers a Continuous Transmission Test Mode to support final application / production tests as well as certification tests. Using this test mode the radio transceiver transmits
continuously a previously transferred frame (PRBS mode) or a continuous wave signal (CW
mode).
In CW mode two different signal frequencies per channel can be transmitted:
• f1 = fCH + 0.5 MHz
• f2 = fCH - 0.5 MHz
Here fCH is the channel center frequency programmed by register 0x08 (PHY_CC_CCA).
Note, in CW mode it is not possible to transmit an RF signal directly on the channel center
frequency.
PSDU data in the Frame Buffer must contain at least a valid PHR (see Section 8.1 “Introduction
- IEEE 802.15.4 - 2006 Frame Format” on page 79) followed by PSDU data. It is recommended
to use a frame of maximum length (127 bytes) and arbitrary PSDU data for the PRBS mode. The
SHR and the PHR are not transmitted. The transmission starts with the PSDU data and is
repeated continuously.
20.2
Configuration
Before enabling Continuous Transmission Test Mode all register configurations shall be done as
follow:
• TX channel setting (optional)
• TX output power setting (optional)
• Mode selection (PRBS / CW)
A register access to register 0x36 and 0x1C enables the Continuous Transmission Test Mode.
The transmission is started by enabling the PLL (TRX_CMD = PLL_ON) and writing the
TX_START command to register 0x02.
Even for CW signal transmission it is required to write valid PSDU data to the Frame Buffer. For
PRBS mode it is recommended to write a frame of maximum length.
The detailed programming sequence is shown in Table 20-1 on page 175. The column R/W
informs about writing (W) or reading (R) a register or the Frame Buffer.
Table 20-1.
Continuous Transmission Programming Sequence.
Step
Action
Register
R/W
Value
Description
1
RESET
2
Register Access
0X0E
W
0x01
Set IRQ mask register, enable IRQ_0 (PLL_LOCK)
3
Register Access
0x04
W
0x00
Disable TX_AUTO_CRC_ON
4
Register Access
0x02
W
0x03
Set radio transceiver state TRX_OFF
5
Register Access
0x03
W
0x01
Set clock at pin 17 (CLKM)
6
Register Access
0x08
W
0x33
Set IEEE 802.15.4 CHANNEL, e.g. 19
7
Register Access
0x05
W
0x00
Set TX output power, e.g. to Pmax
Reset AT86RF231
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8
Register Access
0x01
R
0x08
Verify TRX_OFF state
9
Register Access
0x036
W
0x0F
Enable Continuous Transmission Test Mode - step # 1
10(1)
Register Access
0x0C
W
0x03
Enable High Data Rate Mode, 2 Mb/s
11(1)
Register Access
0x0A
W
0xA7
Configure High Data Rate Mode
12(2)
Frame Buffer
Write Access
W
Write PHR and PSDU data (even for CW mode), refer to
Table 20-2 on page 176.
13
Register Access
0x1C
W
0x54
Enable Continuous Transmission Test Mode - step # 2
14
Register Access
0x1C
W
0x46
Enable Continuous Transmission Test Mode - step # 3
15
Register Access
0x02
W
0x09
Enable PLL_ON state
16
Interrupt event
0x0F
R
0x01
Wait for IRQ_0 (PLL_LOCK)
17
Register Access
0x02
W
0x02
Initiate Transmission, enter BUSY_TX state
18
Measurement
19
Register Access
20
RESET
Note:
Perform measurement
0x1C
W
0x00
Disable Continuous Transmission Test Mode
Reset AT86RF231
1. Only required for CW mode, do not configure for PRBS mode.
2. Frame Buffer content depends on desired transmitter operation mode, either PRBS or CW
mode.
The content of the Frame Buffer has to be defined for Continuous Transmission PRBS mode or
CW mode. To measure the power spectral density (PSD) mask of the transmitter it is recommended to use a random sequence of maximum length for the PSDU data.
To measure CW signals it is necessary to write either 0x00 or 0xFF to the Frame Buffer, for
details refer to Table 20-2 on page 176.
Table 20-2.
Step
12
Frame Buffer Content for various Continuous Transmission Modulation Schemes
Action
Frame Content
Comment
Frame Buffer
Access
Random Sequence
modulated RF signal
0x00 (each byte)
fCH - 0.5 MHz, CW signal
0xFF (each byte)
fCH + 0.5 MHz, CW signal
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20.3
Register Description
Register 0x36 (TST_CTRL_DIGI):
Register TST_CTRL_DIG enables the continuous transmission test mode.
Bit
7
6
+0x36
5
4
3
2
Reserved
1
0
TST_CTRL_DIG
TST_CTRL_DIGI
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
0
0
1
0
0
0
0
0
• Bit [7:4] - Reserved
• Bit [3:0] - TST_CTRL_DIG
These register bits enable continuous transmission:
Table 20-3.
Continuous Transmission
Register Bit
TST_CTRL_DIG
Value
Description
0x0
Continuous Transmission disabled
0xF
Continuous Transmission enabled
0x1 - 0xE
Reserved
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21. Appendix B - AT86RF231-ZF Extended Temperature Range
21.1
Introduction
Appendix B contains information specific to devices operating at temperatures up to 125°C. Only
deviations to the standard device AT86RF231-ZU are covered in this appendix, all other information are similar to previous sections.
Performance figures for 125°C are only valid for device part number AT86RF231-ZF.
21.2
Electrical Characteristics
If not otherwise stated, electrical characteristics for typical operating conditions are similar to figures provided in “Electrical Characteristics” on page 156.
Table 21-1.
Recommended Operating Range
No.
Symbol
Parameter
21.2.1
TOP
Operating temperature range
Condition
Min.
-40
Typ.
Max
Units
+125
°C
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21.3
Typical Characteristics
The following charts showing each a typical behavior of the AT86RF231. These figures are not
tested during manufacturing for all supply voltages and all temperatures. All power consumption
measurements are performed with pin 17 (CLKM) disabled, unless otherwise stated.
Power consumption for the microcontroller required to program the radio transceiver is not
included in the measurement results.
The power consumption in SLEEP state mode is independent from CLKM master clock rate
selection.
The current consumption is a function of several factors such as: operating voltage, operating
frequency, loading of I/O pins, switching rate of I/O pins, and ambient temperature. The dominating factors are operating voltage and ambient temperature.
If possible the measurement results are not affected by current drawn from I/O pins. Register,
SRAM or Frame Buffer read or write accesses are not performed during current consumption
measurements.
21.4
21.4.1
Active Supply Current
P_ON and TRX_OFF states
Figure 21-1. Current Consumption in P_ON State
0.7
125 °C
85 °C
25 °C
0 °C
-40 °C
Current Consumption [mA]
0.6
0.5
0.4
0.3
0.2
0.1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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Figure 21-2. Current Consumption in TRX_OFF State
Current Consumption [mA]
0.5
125 °C
85 °C
25 °C
0 °C
-40 °C
0.4
0.3
0.2
0.1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
21.4.2
PLL_ON state
Figure 21-3. Current Consumption in PLL_ON State
8
125 °C
85 °C
25 °C
0 °C
-40 °C
Current Consumption [mA]
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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21.4.3
RX_ON state
Figure 21-4. Current Consumption in RX_ON State - High Sensitivity
17
16
125 °C
85 °C
Current Consumption [mA]
15
14
13
25 °C
0 °C
-40 °C
12
11
10
9
8
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 21-5. Current Consumption in RX_ON State - High Input Level
17
16
Current Consumption [mA]
15
14
125 °C
13
85 °C
25 °C
0 °C
-40 °C
12
11
10
9
8
7
6
5
4
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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Figure 21-6. Current Consumption in RX_ON State - Reduced Sensitivity
17
16
125 °C
85 °C
Current Consumption [mA]
15
14
13
25 °C
0 °C
-40 °C
12
11
10
9
8
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
21.4.4
TX_BUSY state
Figure 21-7. Current Consumption in TX_BUSY State - Minimum Output Power
18
Current Consumption [mA]
16
14
12
10
125 °C
85 °C
25 °C
0 °C
-40 °C
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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Figure 21-8. Current Consumption in TX_BUSY State - Output Power 0 dBm
18
Current Consumption [mA]
16
125 °C
85 °C
25 °C
0 °C
-40 °C
14
12
10
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 21-9. Current Consumption in TX_BUSY State - Maximum Output Power
18
125 °C
85 °C
25 °C
0 °C
-40 °C
Current Consumption [mA]
16
14
12
10
8
6
4
2
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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21.4.5
SLEEP
Figure 21-10. Current Consumption in SLEEP
10000
Current Consumption [nA]
125 °C
1000
85 °C
100
25 °C
10
-40 °C
1
0.1
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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21.5
State Transition Timing
Figure 21-11. Transition Time from EVDD to P_ON (CLKM available)
500
450
Setting Time [ms]
400
125 °C
-40 °C
85 °C
25 °C
350
300
250
200
150
100
50
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
Figure 21-12. Transition Time from SLEEP to TRX_OFF (IRQ_4 (AWAKE_END))
500
125 °C
-40 °C
85 °C
25 °C
450
Setting Time [ms]
400
350
300
250
200
150
100
50
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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Figure 21-13. Transition Time from TRX_OFF to PLL_ON
140
-40 °C
25 °C
State Transition Time [µs]
120
100
85 °C
125 °C
80
60
40
20
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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21.6
21.6.1
Receiver Performance
Sensitivity
Figure 21-14. Sensitivity
-89
TX Input Level [dBm]
-91
-93
-95
-97
-101
125 °C
85 °C
25 °C
-103
-40 °C
-99
-105
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
21.6.2
Adjacent & Alternate Channel Selectivity (ACRx)
Figure 21-15. Adjacent and Alternate Channel Selectivity
70
125 °C
85 °C
25 °C
-40 °C
60
Selectivity [dB]
50
40
30
20
10
0
-25
-20
-15
-10
-5
0
5
10
15
20
25
Channel Offset [MHz]
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21.6.3
RSSI
Figure 21-16. RSSI
30
-40 °C
25 °C
85 °C
125 °C
RSSI Value
25
20
15
10
5
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
RX Input Level [dBm]
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21.7
21.7.1
Transmitter Performance
TX Output Power vs. TX Power Level
Figure 21-17. TX Output Power vs. TX_PWR (EVDD = 3.0V, CH=19)
6
4
TX Output Power [dBm]
2
0
-2
-4
-6
-8
-10
-12
-14
-40 °C
25 °C
85 °C
125 °C
-16
-18
-20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
TX_PWR [Register Value]
21.7.2
TX Output Power vs. EVDD
Figure 21-18. TX Output Power vs. EVDD (TX_PWR = 0, CH=19)
4
-40 °C
25 °C
85 °C
125 °C
TX Output Power [dBm]
3.5
3
2.5
2
1.5
1
0.5
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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21.7.3
TX Output Power vs. Channel
Figure 21-19. TX Output Power vs. Channel (EVDD = 3.0V, TX_PWR = 0)
4
TX Output Power [dBm]
3.5
-40 °C
25 °C
85 °C
125 °C
3
2.5
2
1.5
1
0.5
0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Channel acct. IEEE802.15.4
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21.7.4
TX EVM vs. EVDD
Figure 21-20. Error Vector Magnitude (EVM) vs. EVDD (TX_PWR = 0, CH=19)
10
Error Vector Magnitude [%]
9
8
125 °C
85 °C
25 °C
-40 °C
7
6
5
4
3
2
1
0
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
EVDD [V]
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22. Appendix C - Errata
22.1
AT86RF231 Rev.A
No known errata
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23. Revision history
23.1
23.2
23.3
Rev.8111C - 09/09
1.
Updated the datasheet with a new device AT86RF231-ZF.
2.
Added “Appendix B - AT86RF231-ZF Extended Temperature Range” on page 178
3.
Editorial updates.
Rev.8111B - 02/09
1.
Updated figures and graphics in sections: 5.,6., 8.,9.,11., 12.and 13.
2.
Changed register and sub-register names in “AT86RF231 Extended Feature Set” on page 128.
3.
Editorial changes.
Rev.8111A - 05/08
1. Initial revision
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References
[1]
IEEE Std 802.15.4™-2006: Wireless Medium Access Control (MAC) and Physical Layer (PHY)
Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs)
[2]
IEEE Std 802.15.4™-2003: Wireless Medium Access Control (MAC) and Physical Layer (PHY)
Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs)
[3]
ANSI / ESD-STM5.1-2001: ESD Association Standard Test Method for electrostatic discharge
sensitivity testing - Human Body Model (HBM).
[4]
ESD-STM5.3.1-1999: ESD Association Standard Test Method for electrostatic discharge
sensitivity testing - Charged Device Model (CDM).
[5]
NIST FIPS PUB 197: Advanced Encryption Standard (AES), Federal Information Processing
Standards Publication 197, US Department of Commerce/NIST, November 26, 2001
[6]
AT86RF231 Software Programming Model
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Table of Contents
Features ..................................................................................................... 1
1
Pin-out Diagram ....................................................................................... 2
1.1
Pin Descriptions .................................................................................................3
1.2
Analog and RF Pins ...........................................................................................5
1.3
Digital Pins .........................................................................................................7
2
Disclaimer ................................................................................................. 9
3
Overview ................................................................................................... 9
4
General Circuit Description .................................................................. 10
5
Application Circuits ............................................................................... 12
6
7
8
9
5.1
Basic Application Schematic ...........................................................................12
5.2
Extended Feature Set Application Schematic .................................................14
Microcontroller Interface ....................................................................... 16
6.1
SPI Timing Description ....................................................................................17
6.2
SPI Protocol .....................................................................................................19
6.3
Radio Transceiver Status information .............................................................24
6.4
Radio Transceiver Identification ......................................................................25
6.5
Sleep/Wake-up and Transmit Signal (SLP_TR) ..............................................27
6.6
Interrupt Logic ..................................................................................................29
Operating Modes .................................................................................... 33
7.1
Basic Operating Mode .....................................................................................33
7.2
Extended Operating Mode ...............................................................................47
Functional Description .......................................................................... 79
8.1
Introduction - IEEE 802.15.4 - 2006 Frame Format ........................................79
8.2
Frame Check Sequence (FCS) .......................................................................85
8.3
Received Signal Strength Indicator (RSSI) .....................................................89
8.4
Energy Detection (ED) .....................................................................................91
8.5
Clear Channel Assessment (CCA) ..................................................................94
8.6
Link Quality Indication (LQI) ............................................................................99
Module Description .............................................................................. 101
9.1
Receiver (RX) ................................................................................................101
9.2
Transmitter (TX) ............................................................................................104
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9.3
Frame Buffer ..................................................................................................107
9.4
Voltage Regulators (AVREG, DVREG) .........................................................110
9.5
Battery Monitor (BATMON) ...........................................................................113
9.6
Crystal Oscillator (XOSC) ..............................................................................116
9.7
Frequency Synthesizer (PLL) ........................................................................121
9.8
Automatic Filter Tuning (FTN) .......................................................................125
10 Radio Transceiver Usage .................................................................... 126
10.1
Frame Receive Procedure .............................................................................126
10.2
Frame Transmit Procedure ............................................................................127
11 AT86RF231 Extended Feature Set ...................................................... 128
11.1
Security Module (AES) ..................................................................................128
11.2
Random Number Generator ..........................................................................136
11.3
High Data Rate Modes ..................................................................................137
11.4
Antenna Diversity ..........................................................................................142
11.5
RX/TX Indicator .............................................................................................147
11.6
RX Frame Time Stamping .............................................................................150
11.7
Frame Buffer Empty Indicator ........................................................................152
11.8
Dynamic Frame Buffer Protection .................................................................154
11.9
Configurable Start-Of-Frame Delimiter ..........................................................155
12 Electrical Characteristics .................................................................... 156
12.1
Absolute Maximum Ratings ...........................................................................156
12.2
Recommended Operating Range ..................................................................156
12.3
Digital Pin Characteristics ..............................................................................157
12.4
Digital Interface Timing Characteristics .........................................................157
12.5
General RF Specifications .............................................................................158
12.6
Transmitter Characteristics ............................................................................159
12.7
Receiver Characteristics ................................................................................160
12.8
Current Consumption Specifications .............................................................161
12.9
Crystal Parameter Requirements ..................................................................161
13 Typical Characteristics ........................................................................ 162
13.1
Active Supply Current ....................................................................................162
13.2
State Transition Timing ..................................................................................167
14 Register Summary ............................................................................... 169
15 Abbreviations ....................................................................................... 171
ii
8111C–MCU Wireless–09/09
AT86RF231
16 Ordering Information ........................................................................... 173
17 Soldering Information .......................................................................... 173
18 Package Thermal Properties ............................................................... 173
19 Package Drawing - 32QN2 ................................................................... 174
20 Appendix A - Continuous Transmission Test Mode ......................... 175
20.1
Overview ........................................................................................................175
20.2
Configuration .................................................................................................175
20.3
Register Description ......................................................................................177
21 Appendix B - AT86RF231-ZF Extended Temperature Range ........... 178
21.1
Introduction ....................................................................................................178
21.2
Electrical Characteristics ...............................................................................178
21.3
Typical Characteristics ..................................................................................179
21.4
Active Supply Current ....................................................................................179
21.5
State Transition Timing ..................................................................................185
21.6
Receiver Performance ...................................................................................187
21.7
Transmitter Performance ...............................................................................189
22 Appendix C - Errata ............................................................................. 192
22.1
AT86RF231 Rev.A ........................................................................................192
23 Revision history ................................................................................... 193
23.1
Rev.8111C - 09/09 ........................................................................................193
23.2
Rev.8111B - 02/09 .........................................................................................193
23.3
Rev.8111A - 05/08 .........................................................................................193
References............................................................................................. 194
Table of Contents....................................................................................... i
iii
8111C–MCU Wireless–09/09
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8111C–MCU Wireless–09/09