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TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication
(NFC) Transceiver IC
1 Device Overview
1.1
Features
1
• Supports Near Field Communication (NFC)
Standards NFCIP-1 (ISO/IEC 18092) and NFCIP‑2
(ISO/IEC 21481)
• Completely Integrated Protocol Handling for
ISO15693, ISO18000-3, ISO14443A/B, and
FeliCa™
• Integrated Encoders, Decoders, and Data Framing
for NFC Initiator, Active and Passive Target
Operation for All Three Bit Rates (106 kbps,
212 kbps, 424 kbps) and Card Emulation
• RF Field Detector With Programmable Wake-Up
Levels for NFC Passive Transponder Emulation
Operation
• RF Field Detector for NFC Physical Collision
Avoidance.
• Integrated State Machine for ISO14443A
Anticollision (Broken Bytes) Operation
(Transponder Emulation or NFC Passive Target)
• Input Voltage Range: 2.7 VDC to 5.5 VDC
1.2
•
•
•
•
Applications
Mobile Devices (Tablets, Handsets)
Secure Pairing ( Bluetooth®, Wi-Fi®, Other Paired
Wireless Networks)
Public Transport or Event Ticketing
Passport or Payment (POS) Reader Systems
1.3
• Programmable Output Power: +20 dBm (100 mW),
+23 dBm (200 mW)
• Programmable I/O Voltage Levels From 1.8 VDC
to 5.5 VDC
• Programmable System Clock Frequency Output
(RF, RF/2, RF/4) from 13.56-MHz or 27.12-MHz
Crystal or Oscillator
• Integrated Voltage Regulator Output for Other
System Components (MCU, Peripherals,
Indicators), 20 mA (Max)
• Programmable Modulation Depth
• Dual Receiver Architecture With RSSI for
Elimination of "Read Holes" and Adjacent Reader
System or Ambient In-Band Noise Detection
• Programmable Power Modes for Ultra Low-Power
System Design (Power Down <1 µA)
• Parallel or SPI Interface (With 127-Byte FIFO)
• Temperature Range: –40°C to 110°C
• 32-Pin QFN Package (5 mm x 5 mm)
•
•
•
•
•
Short-Range Wireless Communication Tasks
(Firmware Updates)
Product Identification or Authentication
Medical Equipment or Consumables
Access Control, Digital Door Locks
Sharing of Electronic Business Cards
Description
The TRF7970A device is an integrated analog front end and data-framing device for a 13.56-MHz RFID
and Near Field Communication (NFC) system. Built-in programming options make the device suitable for a
wide range of applications for proximity and vicinity identification systems.
The device can perform in one of three modes: RFID and NFC reader, NFC peer, or in card emulation
mode. Built-in user-configurable programming options make the device suitable for a wide range of
applications. The TRF7970A device is configured by selecting the desired protocol in the control registers.
Direct access to all control registers allows fine tuning of various reader parameters as needed.
Documentation, reference designs, EVM, and source code TI MSP430™ MCUs or ARM® MCUs are
available.
Device Information
PART NUMBER
TRF7970ARHB
PACKAGE
BODY SIZE
VQFN (32)
5 mm x 5 mm
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
1.4
www.ti.com
Functional Block Diagram
Figure 1-1 shows the block diagram.
VDD_I/O
MUX
RX_IN1
PHASE &
AMPLITUDE
DETECTOR
GAIN
RSSI
(AUX)
RF LEVEL
DETECTOR
RX_IN2
PHASE &
AMPLITUDE
DETECTOR
RSSI
(MAIN)
I/O_1
GAIN
FILTER
& AGC
ISO
PROTOCOL
HANDLING
TRANSMITTER ANALOG
FRONT END
STATE
CONTROL
LOGIC
[CONTROL
REGISTERS &
COMMAND
LOGIC]
DIGITIZER
VDD_PA
TX_OUT
I/O_0
FRAMING
MCU
INTERFACE
I/O_2
I/O_3
LEVEL SHIFTER
RSSI
(EXTERNAL)
LOGIC
127-BYTE
FIFO
I/O_6
I/O_7
SYS_CLK
DATA _CLK
VIN
SERIAL
CONVERSION
CRC & PARITY
VSS_PA
I/O_5
IRQ
DECODER
BIT
FRAMING
I/O_4
VDD_A
BAND_GAP
EN
VSS_A
EN2
DIGITAL CONTROL
STATE MACHINE
ASK/OOK
MOD
OSC_IN
OSC_OUT
VDD_RF
VOLTAGE SUPPLY REGULATOR SYSTEMS
(SUPPLY REGULATORS AND REFERENCE VOLTAGES)
VSS_RF
VDD_X
VSS
CRYSTAL OR OSCILLATOR
TIMING SYSTEM
VSS_D
Figure 1-1. Block Diagram
2
Device Overview
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SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Table of Contents
1
2
3
4
5
Device Overview ......................................... 1
1.1
Features .............................................. 1
1.2
Applications ........................................... 1
1.3
Description ............................................ 1
1.4
Functional Block Diagram ............................ 2
Revision History ......................................... 4
Device Characteristics .................................. 5
Terminal Configuration and Functions .............. 6
4.1
Pin Assignments ...................................... 6
4.2
Terminal Functions ................................... 7
............................................ 9
.......................... 9
5.2
Recommended Operating Conditions ................ 9
5.3
Electrical Characteristics ............................ 10
5.4
Handling Ratings .................................... 11
5.5
Thermal Characteristics ............................. 11
5.6
Switching Characteristics ........................... 11
Detailed Description ................................... 12
6.1
Overview ............................................ 12
6.2
System Block Diagram .............................. 15
6.3
Power Supplies ...................................... 15
6.4
Receiver – Analog Section .......................... 21
6.5
Receiver – Digital Section ........................... 22
6.6
Oscillator Section ................................... 27
6.7
Transmitter – Analog Section ....................... 28
Specifications
5.1
6
7
6.8
6.9
Transmitter – Digital Section ........................ 28
Transmitter – External Power Amplifier and
Subcarrier Detector ................................. 29
6.10
6.11
TRF7970A IC Communication Interface ............ 30
Special Direct Mode for Improved MIFARE™
Compatibility ......................................... 48
6.12
NFC Modes.......................................... 48
6.13
Direct Commands from MCU to Reader ............ 51
6.14
Register Description ................................. 55
Application Schematic and Layout
Considerations.......................................... 75
7.1
Absolute Maximum Ratings
7.2
8
9
TRF7970A Reader System Using Parallel
Microcontroller Interface............................. 75
TRF7970A Reader System Using SPI With SS
Mode ................................................ 76
..............................
......
7.5
Reader Antenna Design Guidelines ................
Device and Documentation Support ...............
8.1
Documentation Support .............................
8.2
Community Resources ..............................
8.3
Trademarks..........................................
8.4
Electrostatic Discharge Caution .....................
8.5
Glossary .............................................
7.3
Layout Considerations
77
7.4
Impedance Matching TX_Out (Pin 5) to 50 Ω
77
79
80
80
80
80
80
80
Mechanical Packaging and Orderable
Information .............................................. 80
9.1
Packaging Information
..............................
Table of Contents
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3
TRF7970A
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2 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision J (February 2014) to Revision K
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
4
Page
Changed Figure 1-1 to show 127-byte FIFO ...................................................................................... 2
Moved Section 3 ...................................................................................................................... 5
Changed title of Section 4 .......................................................................................................... 6
Changed title of Section 5 ........................................................................................................... 9
Added ASK/OOK and MOD to VIL and VIH ........................................................................................ 9
Moved Section 5.3 .................................................................................................................. 10
Changed VDD_A TYP value from 3.5 V to 3.4 V ................................................................................. 10
Moved Section 5.4 .................................................................................................................. 11
Added V(ESD) MIN values, test specifications, and notes ....................................................................... 11
Changed title of Section 5.5 from Dissipation Ratings to Thermal Characteristics ......................................... 11
Moved Section 5.6 .................................................................................................................. 11
Changed title of Section 6 .......................................................................................................... 12
Moved previous Section 3, Device Overview, to Section 6.1.................................................................. 12
Changed from "By default, the AGC is frozen after..." to "By default, the AGC window comparator is set after..." ... 21
Changed from "TX Pulse Length Control register (0x05)" to "TX Pulse Length Control register (0x06)" ............... 28
Changed from "18.8 s" to "18.8 µs" in the sentence that starts with "If the register contains all zeros..."............... 28
Changed Table 6-18 to match Table 6-43 ....................................................................................... 50
Changed command 0x18 to "Test internal RF" ................................................................................. 51
Changed command 0x19 to "Test external RF" ................................................................................ 51
Moved Section 6.14 ................................................................................................................. 55
Changed the sentence that starts "The AGC action is fast..." from "finishes after four subcarrier pulses" to
"finishes within eight subcarrier pulses" ......................................................................................... 64
Moved Section 7..................................................................................................................... 75
Deleted previous Section 10, System Design, and moved contents to Section 7.3 through Section 7.5 ............... 77
Removed references to figure numbers in Figure 7-3 .......................................................................... 78
Revision History
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3 Device Characteristics
Table 3-1 shows the supported modes of operation for the TRF7970A device.
Table 3-1. Supported Modes of Operation
P2P Initiator or Reader/Writer
(1)
Technology
Bit rate
(kbps)
NFC-A/B (ISO14443A/B)
Card Emulation
P2P Target
Technology
Bit rate
(kbps)
Technology
Bit rate
(kbps)
106, 212, 424,
848 (1)
NFC-A/B
106
NFC-A
106
NFC-F (JIS: X6319-4)
212, 424
N/A
N/A
NFC-F
212, 424
NFC-V (ISO15693)
6.7, 26.7
N/A
N/A
N/A
N/A
848 kbps only applies to reader/writer mode.
Device Characteristics
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4 Terminal Configuration and Functions
4.1
Pin Assignments
Figure 4-1 shows the pin assignments for the 32-pin RHB package.
VDD_X
OSC_IN
OSC_OUT
VSS_D
EN
SYS_CLK
DATA_CLK
EN2
32
31
30
29
28
27
26
25
VDD_A
1
24
I/0_7
VIN
2
23
I/0_6
VDD_RF
3
22
I/0_5
VDD_PA
4
21
I/0_4
TX_OUT
5
20
I/0_3
VSS_PA
6
19
I/0_2
VSS_RX
7
18
I/0_1
RX_IN1
8
17
I/0_0
Pad
12
13
14
15
ASK/OOK
IRQ
MOD
VSS_A
16
VDD_I/O
11
BG
RX_IN2
10
VSS
9
Figure 4-1. 32-Pin RHB Package (Top View)
6
Terminal Configuration and Functions
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4.2
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Terminal Functions
Table 4-1 describes the signals.
Table 4-1. Terminal Functions
TERMINAL
NAME
NO.
TYPE
(1)
DESCRIPTION
VDD_A
1
OUT
Internal regulated supply (2.7 V to 3.4 V) for analog circuitry
VIN
2
SUP
External supply input to chip (2.7 V to 5.5 V)
VDD_RF
3
OUT
Internal regulated supply (2.7 V to 5 V), normally connected to VDD_PA (pin 4)
VDD_PA
4
INP
Supply for PA; normally connected externally to VDD_RF (pin 3)
TX_OUT
5
OUT
RF output (selectable output power, 100 mW or 200 mW, with VDD = 5 V)
VSS_PA
6
SUP
Negative supply for PA; normally connected to circuit ground
VSS_RX
7
SUP
Negative supply for RX inputs; normally connected to circuit ground
RX_IN1
8
INP
Main RX input
RX_IN2
9
INP
Auxiliary RX input
VSS
10
SUP
Chip substrate ground
BAND_GAP
11
OUT
Bandgap voltage (VBG = 1.6 V); internal analog voltage reference
ASK/OOK
12
BID
IRQ
13
OUT
Interrupt request
INP
External data modulation input for Direct Mode 0 or 1
OUT
Subcarrier digital data output (see registers 0x1A and 0x1B)
Selection between ASK and OOK modulation (0 = ASK, 1 = OOK) for Direct Mode 0 or 1.
Can be configured as an output to provide the received analog signal output.
MOD
14
VSS_A
15
SUP
Negative supply for internal analog circuits; connected to GND
VDD_I/O
16
INP
Supply for I/O communications (1.8 V to VIN) level shifter. VIN should be never exceeded.
I/O_0
17
BID
I/O pin for parallel communication
I/O_1
18
BID
I/O pin for parallel communication
I/O_2
19
BID
I/O_3
20
BID
I/O_4
21
BID
I/O_5
22
BID
I/O_6
23
BID
I/O pin for parallel communication
TX Enable (in Special Direct Mode)
I/O pin for parallel communication
TX Data (in Special Direct Mode)
I/O pin for parallel communication
Slave Select signal in SPI mode
I/O pin for parallel communication
Data clock output in Direct Mode 1 and Special Direct Mode
I/O pin for parallel communication
MISO for serial communication (SPI)
Serial bit data output in Direct Mode 1 or subcarrier signal in Direct Mode 0
I/O pin for parallel communication.
I/O_7
24
BID
EN2
25
INP
Selection of power down mode. If EN2 is connected to VIN, then VDD_X is active during power
down mode 2 (for example, to supply the MCU).
DATA_CLK
26
INP
Data Clock input for MCU communication (parallel and serial)
OUT
If EN = 1 (EN2 = don't care) the system clock for MCU is configured. Depending on the crystal
that is used, options are as follows (see register 0x09):
13.56-MHz crystal: Off, 3.39 MHz, 6.78 MHz, or 13.56 MHz
27.12-MHz crystal: Off, 6.78 MHz, 13.56 MHz, or 27.12 MHz
SYS_CLK
27
MOSI for serial communication (SPI)
If EN = 0 and EN2 = 1, then system clock is set to 60 kHz
EN
28
INP
Chip enable input (If EN = 0, then chip is in sleep or power-down mode).
VSS_D
29
SUP
Negative supply for internal digital circuits
(1)
SUP = Supply, INP = Input, BID = Bidirectional, OUT = Output
Terminal Configuration and Functions
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Table 4-1. Terminal Functions (continued)
TERMINAL
NAME
OSC_OUT
NO.
30
TYPE
(1)
DESCRIPTION
OUT
Crystal or oscillator output
INP
Crystal or oscillator input
OUT
Crystal oscillator output
OSC_IN
31
VDD_X
32
OUT
Internally regulated supply (2.7 V to 3.4 V) for digital circuit and external devices (for example,
MCU)
PAD
SUP
Chip substrate ground
Thermal Pad
8
Terminal Configuration and Functions
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5 Specifications
5.1
Absolute Maximum Ratings
(1) (2)
over operating free-air temperature range (unless otherwise noted)
VIN
Input voltage range
IIN
Maximum current VIN
TJ
Maximum operating virtual junction temperature
(1)
(2)
(3)
5.2
-0.3 V to 6 V
150 mA
Any condition
140°C
Continuous operation, long-term reliability
(3)
125°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under Operating Conditions are not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to substrate ground terminal VSS.
The maximum junction temperature for continuous operation is limited by package constraints. Operation above this temperature may
result in reduced reliability or lifetime of the device.
Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
TYP
MAX
UNIT
VIN
Operating input voltage
2.7
5
5.5
V
TA
Operating ambient temperature
-40
25
110
°C
TJ
Operating virtual junction temperature
-40
25
125
°C
VIL
Input voltage - logic low
I/O lines, IRQ, SYS_CLK, DATA_CLK,
EN, EN2, ASK/OOK, MOD
0.2 x
VDD_I/O
V
VIH
Input voltage threshold, logic high
I/O lines, IRQ, SYS_CLK, DATA_CLK,
EN, EN2, ASK/OOK, MOD
0.8 x
VDD_I/O
V
Specifications
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5.3
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Electrical Characteristics
TYP operating conditions are TA = 25°C, VIN = 5 V, full-power mode (unless otherwise noted)
MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
0.5
5
µA
IPD1
Supply current in Power Down Mode 1
All building blocks disabled, including supplyvoltage regulators; measured after 500-ms
settling time (EN = 0, EN2 = 0)
IPD2
Supply current in Power Down Mode 2
(Sleep Mode)
The SYS_CLK generator and VDD_X remain
active to support external circuitry; measured
after 100-ms settling time (EN = 0, EN2 = 1)
120
200
µA
ISTBY
Supply current in stand-by mode
Oscillator running, supply-voltage regulators in
low-consumption mode (EN = 1, EN2 = x)
1.9
3.5
mA
ION1
Supply current without antenna driver
current
Oscillator, regulators, RX and AGC active, TX
is off
10.5
14
mA
ION2
Supply current – TX (half power)
Oscillator, regulators, RX and AGC and TX
active, POUT = 100 mW
70
78
mA
ION3
Supply current – TX (full power)
Oscillator, regulators, RX and AGC and TX
active, POUT = 200 mW
130
150
mA
VPOR
Power-on reset voltage
Input voltage at VIN
1.4
2
2.6
V
VBG
Bandgap voltage (pin 11)
Internal analog reference voltage
1.5
1.6
1.7
V
VDD_A
Regulated output voltage for analog
circuitry (pin 1)
VIN = 5 V
3.1
3.4
3.8
V
VDD_X
Regulated supply for external circuitry
Output voltage pin 32, VIN = 5 V
3.1
3.4
3.8
V
IVDD_Xmax
Maximum output current of VDD_X
Output current pin 32, VIN = 5 V
20
mA
RRFOUT
Antenna driver output resistance
RRFIN
RX_IN1 and RX_IN2 input resistance
VRF_INmax
Maximum RF input voltage at RX_IN1 and
RX_IN2
VRF_INmin
(1)
Half-power mode, VIN = 2.7 V to 5.5 V
8
12
Full-power mode, VIN = 2.7 V to 5.5 V
4
6
10
20
4
VRF_INmax should not exceed VIN
3.5
Minimum RF input voltage at RX_IN1 and
RX_IN2 (input sensitivity) (2)
fSUBCARRIER= 424 kHz
1.4
2.5
fSUBCARRIER = 848 kHz
2.1
3
fSYS_CLK
SYS_CLK frequency
In power mode 2, EN = 0, EN2 = 1
60
120
fC
Carrier frequency
Defined by external crystal
tCRYSTAL
Crystal run-in time
Time until oscillator stable bit is set (register
0x0F) (3)
fD_CLKmax
Maximum DATA_CLK frequency (4)
Depends on capacitive load on the I/O lines,
recommendation is 2 MHz (4)
ROUT
RSYS_CLK
(1)
(2)
(3)
(4)
10
25
kΩ
Vpp
13.56
mVpp
kHz
MHz
3
2
Ω
ms
8
10
MHz
Output resistance I/O_0 to I/O_7
500
800
Ω
Output resistance RSYS_CLK
200
400
Ω
Antenna driver output resistance
Measured with subcarrier signal at RX_IN1 or RX_IN2 and measured the digital output at MOD pin with register 0x1A bit 6 = 1.
Depends on the crystal parameters and components
Recommended DATA_CLK speed is 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not
exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output
resistance of 400 Ω (12-ns time constant when 30-pF load used).
Specifications
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5.4
Handling Ratings
TSTG
Storage temperature range
V(ESD)
(1)
(2)
Electrostatic discharge
Human-Body Model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins
(1)
MIN
MAX
UNIT
-55
150
°C
-2
2
kV
Charged-Device Model (CDM), per JEDEC specification JESD22-C101,
all pins (2)
-500
500
V
Machine Model (MM)
-200
200
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as 2 kV
may actually have higher performance.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Pins listed as 500 V
may actually have higher performance.
5.5
(1)
(2)
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Thermal Characteristics
PACKAGE
θJC
θJA (1)
RHB (32 pin)
31°C/W
36.4°C/W
POWER RATING (2)
TA ≤ 25°C
TA ≤ 85°C
2.7 W
1.1 W
This data was taken using the JEDEC standard high-K test PCB.
Power rating is determined with a junction temperature of 125°C. This is the point where distortion starts to increase substantially.
Thermal management of the final PCB should strive to keep the junction temperature at or below 125°C for best performance and longterm reliability.
5.6
Switching Characteristics
TYP operating conditions are TA = 25°C, VIN = 5 V, full-power mode (unless otherwise noted)
MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
250
62.5
50
UNIT
tLO/HI
DATA_CLK time high or low, one half of
DATA_CLK at 50% duty cycle
tSTE,LEAD
Slave select lead time, slave select low to
clock
200
ns
tSTE,LAG
Slave select lag time, last clock to slave
select high
200
ns
tSTE,DIS
Slave select disable time, slave select
rising edge to next slave select falling
edge
tSU,SI
tHD,SI
Depends on capacitive load on the I/O lines
(1)
ns
300
ns
MOSI input data setup time
15
ns
MOSI input data hold time
15
ns
tSU,SO
MISO input data setup time
15
ns
tHD,SO
MISO input data hold time
tVALID,SO
MISO output data valid time
(1)
15
DATA_CLK edge to MISO valid, CL ≤ 30 pF
30
ns
50
75
ns
Recommended DATA_CLK speed is 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not
exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output
resistance of 400 Ω (12-ns time constant when 30-pF load used).
Specifications
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6 Detailed Description
6.1
6.1.1
Overview
RFID and NFC Operation – Reader and Writer
The TRF7970A is a high performance 13.56-MHz HF RFID and NFC Transceiver IC composed of an
integrated analog front end (AFE) and a built-in data framing engine for ISO15693, ISO14443A/B, and
FeliCa. This includes data rates up to 848 kbps for ISO14443 with all framing and synchronization tasks
on board (in default mode). The TRF7970A also supports NFC Tag Type 1, 2, 3, and 4 operations. This
architecture enables the customer to build a complete cost-effective yet high-performance multi-protocol
13.56-MHz RFID and NFC system together with a low-cost microcontroller.
Other standards and even custom protocols can be implemented by using either of the Direct Modes that
the device offers. These Direct Modes (0 and 1) allow the user to fully control the analog front end (AFE)
and also gain access to the raw subcarrier data or the unframed but already ISO formatted data and the
associated (extracted) clock signal.
The receiver system has a dual input receiver architecture. The receivers also include various automatic
and manual gain control options. The received input bandwidth can be selected to cover a broad range of
input subcarrier signal options.
The received signal strength from transponders, ambient sources, or internal levels is available through
the RSSI register. The receiver output is selectable among a digitized subcarrier signal and any of the
integrated subcarrier decoders. The selected subcarrier decoder delivers the data bit stream and the data
clock as outputs.
The TRF7970A also includes a receiver framing engine. This receiver framing engine performs the CRC
or parity check, removes the EOF and SOF settings, and organizes the data in bytes for ISO14443A/B,
ISO15693, and FeliCa protocols. Framed data is then accessible to the microcontroller (MCU) through a
127-byte FIFO register.
VDD
VDD_X
VDD
VDD_I/O
TX_OUT
Matching
TRF7970A
RX_IN 1
RX_IN2
VSS
Crystal
13.56 MHz
MCU
(MSP430/ARM)
Parallel
or SPI
XIN
VIN
Supply: 2.7 V – 5.5 V
Figure 6-1. Application Block Diagram
A parallel or serial interface (SPI) can be used for the communication between the MCU and the
TRF7970A reader. When the built-in hardware encoders and decoders are used, transmit and receive
functions use a 127-byte FIFO register. For direct transmit or receive functions, the encoders and
decoders can be bypassed so that the MCU can process the data in real time. The TRF7970A supports
data communication voltage levels from 1.8 V to 5.5 V for the MCU I/O interface. The transmitter has
selectable output-power levels of 100 mW (+20 dBm) or 200 mW (+23 dBm) equivalent into a 50-Ω load
when using a 5-V supply.
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The transmitter supports OOK and ASK modulation with selectable modulation depth. The TRF7970A also
includes a data transmission engine that comprises low-level encoding for ISO15693, ISO14443A/B and
FeliCa. Included with the transmit data coding is the automatic generation of Start Of Frame (SOF), End
Of Frame (EOF), Cyclic Redundancy Check (CRC), or parity bits.
Several integrated voltage regulators ensure a proper power-supply noise rejection for the complete
reader system. The built-in programmable auxiliary voltage regulator VDD_X (pin 32), is able to deliver up to
20 mA to supply a microcontroller and additional external circuits within the reader system.
6.1.2
NFC Device Operation – Initiator
The desired system of operation (bit rate) is achieved by selecting the option bits in control registers in the
same way as for RFID reader operation. Also the communication to external MCU and data exchange is
identical.
The transmitting system comprises an RF level detector (programmable level) which is used for initial (or
response) RF collision avoidance. The RF collision avoidance sequence is started by sending a direct
command. If successful, the NFC initiator can send the data or commands, the MCU has loaded in the
FIFO register. The coding of this data is done by hardware coders either in ISO14443A/B format or in
FeliCa format. The coders also provide CRC and parity bits (if required) and automatically add preambles,
SOF, EOF, and synchronization bytes as defined by selected protocol.
The receiver system offers same analog features (AGC, AM/PM, bandwidth selection, etc.) as described
previously in RFID and NFC reader and writer description. The system comprises integrated decoders for
passive targets (ISO14443A/B tag or FeliCa) or active targets (ISO14443A/B reader or FeliCa). For all this
options, the system also supports framing including CRC and parity check and removal of SOF, EOF, and
synchronization bytes as specified by the selected protocol.
6.1.3
NFC Device Operation – Target
The desired system of operation (bit rate) is achieved by selecting the option bits in control registers in the
same way as for RFID reader or NFC initiator operation. Also the communication to external MCU and
data exchange is identical.
The activation of NFC target is done when a sufficient RF field level is detected on the antenna. The level
needed for wake-up is selectable and is stored in non-volatile register.
When the activation occurs, the system performs automatic power-up and waits for the first command to
be received. Based on this command, the system knows if it should operate as passive or active target
and at what bit rate. After activation, the receiver system offers the same analog features (for example,
AGC, AM/PM, and bandwidth selection) as in the case of an RFID reader.
When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip
keeps the supply system on. If EN2 = L and EN = L, the chip is in complete power down. To operate as
NFC target or Tag emulator, the MCU must load a value different from zero (0) in Target Detection Level
register (B0-B2) to enable the RF measurement system (supplied by VEXT, so it can operate also during
complete power down and consumes only 3.5 µA). The RF measurement constantly monitors the RF
signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the in
Target Detection Level register, the chip is automatically activated (EN is internally forced high).
When the voltage supply system and the oscillator are started and are stable, osc_ok goes high (B6 of
RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).
Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly
also during normal operation). This informs the MCU that the chip should start operation as NFC TARGET
device. When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set
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in IRQ register. The MCU must set EN = H (confirm the power-up) in the time between the two IRQs,
because the internal power-up ends after the second IRQ. The type and coding of the first initiator (or
reader in the case of a tag emulator) command defines the communication protocol type that the target
must use. Therefore, the communication protocol type is available in the NFC Target Protocol register
immediately after receiving the first command.
Based on the first command from the INITIATOR, the following actions are taken:
• If the first command is SENS_REQ or ALL_REQ the TARGET must enter the SDD protocol for 106kbps passive communication to begin; afterward, the baud rate can be changed to 212 kbps or 424
kbps, according to the system requirements. If bit B5 in the NFC Target Detection Level register is not
set, the MCU handles the SDD and the command received is send to FIFO. If the RF field is turned off
(B7 in NFC Target Protocol register is low) at any time, the system sends an IRQ to the MCU with bit
B2 (RF field change) in the IRQ register set high. This informs the MCU that the procedure was
aborted and the system must be reset. The clock extractor is automatically activated in this mode.
• If the command is SENS_REQ or ALL_REQ and the card emulation bit in ISO Control register is set,
the system emulates an ISO14443A/B tag. The procedure does not differ from the one previously
described for the case of a passive target at 106 kbps. The clock extractor is automatically activated in
this mode. To emulate a FeliCa card, the ISO Control register must be set for passive target mode at
either 212 kbps or 424 kbps.
• If the first command is a POLLING request, the system becomes the TARGET in passive
communication using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU
directly. The POLLING response is sent in one of the slots automatically calculated by the MCU (first
slot starts 2.416 ms after end of command, and slots follow in 1.208 ms).
• If the first command is ATR_REQ, the system operates as an active TARGET using the same
communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled
by MCU. The chip is only required to time the response collision avoidance, which is done on direct
command from MCU. When the RF field is switched on and the minimum wait time is elapsed, the chip
sends an IRQ with B1 (RF collision avoidance finished) set high. This signals the MCU that it can send
the reply.
• If the first command is coded as ISO14443B and the Tag emulation bit is set in the ISO Control
register, the system enters ISO14443B emulation mode. The anticollision must be handled by the
MCU, and the chip provides all physical level coding, decoding, and framing for this protocol.
6.1.3.1
Active Target
If the first command received by the RF interface defines the system as an active target, then the receiver
selects the appropriate data decoders (ISO14443A\B reader or FeliCa) and framing option. Only the raw
(decoded) data is forwarded to the MCU through the FIFO. SOF, EOF, preamble, sync bytes, CRC, and
parity bytes are checked by the framer and discarded.
The transmitting system includes an RF level detector (programmable level) that is used for RF collision
avoidance. The RF collision avoidance sequence is started by sending a direct command. If successful,
the NFC initiator can send the data that the MCU has loaded in the FIFO register. The coding of this data
is done by hardware coders either in ISO14443A format (106-kbps system) or in FeliCa format for (212kbps and 424-kbps systems). The coders also provide CRC and parity bits (if required) and automatically
add preambles, SOF, EOF, and synchronization bytes as defined by selected protocol.
6.1.3.2
Passive Target
If the first command received by the RF interface defines the system as a passive target, then the receiver
selects the appropriate data decoders (ISO14443A\B reader or FeliCa) and framing option. Again, only the
raw (decoded) data is forwarded to the MCU through the FIFO; SOF, EOF, preamble, sync bytes, CRC,
and parity bytes are checked by the framer and discarded. The receiver works same as in the case of an
active target.
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The transmit system in passive target mode differs from active target and operates similar to the standard
tag. There is no automatic RF collision avoidance sequence, and encoders are used to code the data for
ISO14443A\B tag (at 106 kbps, to start) or FeliCa (at 212 kbps, to start) format. The collision avoidance
must be handled by the firmware on the connected MCU. The coding system adds all of the SOF, EOF,
CRC, parity bits, and synchronization bytes that are required by protocol. On the physical level, the
modulation of the initiator's RF field is done by changing the termination impedance of the antenna
between 4 Ω and open.
6.1.3.3
Card Emulation
The chip can enter this mode by setting appropriate option bits. There are two options to emulate a card.
For ISO14443A\B, the emulation supports 106-kbps data rate to start. For ISO14443A, the anticollision
algorithm can be performed using an internal state machine, which relieves the MCU of any real-time
tasks. The unique ID required for anticollision is provided by the MCU after wake-up of the system.
6.2
System Block Diagram
Figure 6-2 shows a block diagram of the TRF7970A.
VDD_I/O
MUX
RX_IN1
PHASE &
AMPLITUDE
DETECTOR
GAIN
RSSI
(AUX)
RF LEVEL
DETECTOR
PHASE &
AMPLITUDE
DETECTOR
TRANSMITTER ANALOG
FRONT END
STATE
CONTROL
LOGIC
I/O_1
[CONTROL
REGISTERS &
COMMAND
LOGIC]
RSSI
(MAIN)
GAIN
FILTER
& AGC
DIGITIZER
ISO
PROTOCOL
HANDLING
DECODER
VDD_PA
TX_OUT
I/O_0
FRAMING
BIT
FRAMING
MCU
INTERFACE
I/O_2
I/O_3
LEVEL SHIFTER
RSSI
(EXTERNAL)
RX_IN2
LOGIC
I/O_5
I/O_6
I/O_7
IRQ
127-BYTE
FIFO
SERIAL
CONVERSION
CRC & PARITY
VSS_PA
I/O_4
SYS_CLK
DATA _CLK
VIN
VDD_A
BAND_GAP
EN
EN2
ASK/OOK
MOD
OSC_IN
OSC_OUT
VSS_A
DIGITAL CONTROL
STATE MACHINE
VDD_RF
VOLTAGE SUPPLY REGULATOR SYSTEMS
(SUPPLY REGULATORS AND REFERENCE VOLTAGES)
VSS_RF
VDD_X
VSS
CRYSTAL OR OSCILLATOR
TIMING SYSTEM
VSS_D
Figure 6-2. System Block Diagram
6.3
Power Supplies
The TRF7970A positive supply input VIN (pin 2) sources three internal regulators with output voltages
VDD_RF, VDD_A and VDD_X. All regulators use external bypass capacitors for supply noise filtering and must
be connected as indicated in reference schematics. These regulators provide a high power supply reject
ratio (PSRR) as required for RFID reader systems. All regulators are supplied by VIN (pin 2).
The regulators are not independent and have common control bits in register 0x0B for output voltage
setting. The regulators can be configured to operate in either automatic or manual mode (register 0x0B,
bit 7). The automatic regulator setting mode ensures an optimal compromise between PSRR and the
highest possible supply voltage for RF output (to ensure maximum RF power output). The manual mode
allows the user to manually configure the regulator settings.
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6.3.1
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Supply Arrangements
Regulator Supply Input: VIN
The positive supply at VIN (pin 2) has an input voltage range of 2.7 V to 5.5 V. VIN provides the supply
input sources for three internal regulators with the output voltages VDD_RF, VDD_A, and VDD_X. External
bypass capacitors for supply noise filtering must be used (per reference schematics).
NOTE
VIN must be the highest voltage supplied to the TRF7970A.
RF Power Amplifier Regulator: VDD_RF
The VDD_RF (pin 3) regulator is supplying the RF power amplifier. The voltage regulator can be set for
either 5-V or 3-V operation. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 5-V manual-operation, the VDD_RF output voltage can be set
from 4.3 V to 5 V in 100-mV steps. In 3-V manual-operation, the output can be programmed from 2.7 V to
3.4 V in 100-mV steps. The maximum output current capability for 5-V operation is 150 mA and for 3-V
operation is 100 mA.
Analog Supply Regulator: VDD_A
Regulator VDD_A (pin 1) supplies the analog circuits of the device. The output voltage setting depends on
the input voltage and can be set for 5-V and 3-V operation. When configured for 5-V manual-operation,
the output voltage is fixed at 3.4 V. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 3-V manual-operation, the VDD_A output can be set from 2.7 V
to 3.4 V in 100-mV steps (see Table 6-2).
Note: the configuration of VDD_A and VDD_X regulators are not independent from each other. The VDD_A
output current should not exceed 20 mA.
Digital Supply Regulator: VDD_X
The digital supply regulator VDD_X (pin 32) provides the power for the internal digital building blocks and
can also be used to supply external electronics within the reader system. When configured for 3-V
operation, the output voltage can be set from 2.7 to 3.4 V in 100-mV steps. External bypass capacitors for
supply noise filtering must be used (per reference schematics).
Note: the configuration of the VDD_A and VDD_X regulators are not independent from each other. The VDD_X
output current should not exceed 20 mA.
The RF power amplifier regulator (VDD_RF), analog supply regulator (VDD_A) and digital supply regulator
(VDD_X) can be configured to operate in either automatic or manual mode described in Section 6.3.2. The
automatic regulator setting mode ensures an optimal compromise between PSRR and the highest
possible supply voltage to ensure maximum RF power output.
By default, the regulators are set in automatic regulator setting mode. In this mode, the regulators are
automatically set every time the system is activated by setting EN input High or each time the automatic
regulator setting bit, B7 in register 0x0B is set to a 1. The action is started on the 0 to 1 transition. This
means that, if the user wants to re-run the automatic setting from a state in which the automatic setting bit
is already high, the automatic setting bit (B7 in register 0x0B) should be changed: 1-0-1.
By default, the regulator setting algorithm sets the regulator outputs to a "Delta Voltage" of 250 mV below
VIN, but not higher than 5 V for VDD_RF and 3.4 V for VDD_A and VDD_A. The "Delta Voltage" in automatic
regulator mode can be increased up to 400 mV (for details, see bits B0 to B2 in register 0x0B).
16
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Power Amplifier Supply: VDD_PA
The power amplifier of the TRF7970A is supplied through VDD_PA(pin 4). The positive supply pin for the RF
power amplifier is externally connected to the regulator output VDD_RF (pin 3).
I/O Level Shifter Supply: VDD_I/O
The TRF7970A has a separate supply input VDD_I/O (pin 16) for the built-in I/O level shifter. The supported
input voltage ranges from 1.8 V to VIN, not exceeding 5.5 V. Pin 16 is used to supply the I/O interface pins
(I/O_0 to I/O_7), IRQ, SYS_CLK, and DATA_CLK pins of the reader. In typical applications, VDD_I/O is
directly connected to VDD_X, while VDD_X also supplies the MCU. This ensures that the I/O signal levels of
the MCU match the logic levels of the TRF7970A.
Negative Supply Connections: VSS, VSS_TX, VSS_RX, VSS_A, VSS_PA
The negative supply connections VSS_X of each functional block are all externally connected to GND.
The substrate connection is VSS (pin 10), the analog negative supply is VSS_A (pin 15), the logic negative
supply is VSS_D (pin 29), the RF output stage negative supply is VSS_PA (pin 6), and the negative supply for
the RF receiver VSS_RX (pin 7).
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6.3.2
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Supply Regulator Settings
The input supply voltage mode of the reader needs to be selected. This is done in the Chip Status Control
register (0x00). Bit 0 in register 0x00 selects between 5-V or 3-V input supply voltage. The default
configuration is 5 V, which reflects an operating supply voltage range of 4.3 V to 5.5 V. If the supply
voltage is below 4.3 V, the 3-V configuration should be used.
The various regulators can be configured to operate in automatic or manual mode. This is done in the
Regulator and I/O Control register (0x0B) as shown in Table 6-1 and Table 6-2.
Table 6-1. Supply Regulator Setting: 5-V System
Register
Address
(hex)
Option Bits Setting in Regulator Control Register
B7
B6
(1)
B5
B4
B3
B2
B1
B0
Comments
Automatic Mode (default)
0B
1
x
x
x
x
x
0
0
Automatic regulator setting 400-mV difference
0B
0
x
x
x
x
1
1
1
VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
1
0
VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
0
1
VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
0
0
VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
1
1
VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
1
0
VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
0
1
VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
0
0
VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V
Manual Mode
(1)
x = Don't care
Table 6-2. Supply Regulator Setting: 3-V System
Register
Address
(hex)
Option Bits Setting in Regulator Control Register
B7
B6
(1)
B5
B4
B3
B2
B1
B0
Comments
Automatic Mode (default)
0B
1
x
x
x
x
x
0
0
Automatic regulator setting 400-mV difference
0B
0
x
x
x
x
1
1
1
VDD_RF = 3.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
1
0
VDD_RF = 3.3 V, VDD_A = 3.3 V, VDD_X = 3.3 V
0B
0
x
x
x
x
1
0
1
VDD_RF = 3.2 V, VDD_A = 3.2 V, VDD_X = 3.2 V
0B
0
x
x
x
x
1
0
0
VDD_RF = 3.1 V, VDD_A = 3.1 V, VDD_X = 3.1 V
0B
0
x
x
x
x
0
1
1
VDD_RF = 3.0 V, VDD_A = 3.0 V, VDD_X = 3.0 V
0B
0
x
x
x
x
0
1
0
VDD_RF = 2.9 V, VDD_A = 2.9 V, VDD_X = 2.9 V
0B
0
x
x
x
x
0
0
1
VDD_RF = 2.8 V, VDD_A = 2.8 V, VDD_X = 2.8 V
0B
0
x
x
x
x
0
0
0
VDD_RF = 2.7 V, VDD_A = 2.7 V, VDD_X = 2.7 V
Manual Mode
(1)
x = Don't care
The regulator configuration function adjusts the regulator outputs by default to 400 mV below VIN level, but
not higher than 5 V for VDD_RF, 3.4 V for VDD_A and VDD_X. This ensures the highest possible supply
voltage for the RF output stage while maintaining an adequate PSRR (power supply rejection ratio).
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Power Modes
The chip has several power states, which are controlled by two input pins (EN and EN2) and several bits
in the chip status control register (0x00) (see Table 6-3 and Table 6-4).
Table 6-3. 3.3-V Operation Power Modes (1)
EN2
EN
Chip
Status
Control
Register
(0x00)
Power Down
0
0
XX
XX
OFF
OFF
OFF
OFF
OFF
<0.001
-
Sleep Mode
1
0
XX
XX
OFF
OFF
OFF
ON
ON
0.120
-
Standby Mode at
+3.3 VDC
X
1
80
00
OFF
OFF
ON
X
ON
2
-
Mode 1 at +3.3 VDC
X
1
00
00
OFF
OFF
ON
X
ON
3
-
Mode 2 at +3.3 VDC
X
1
02
00
OFF
ON
ON
X
ON
9
-
Mode 3 (Half Power) at
+3.3 VDC
X
1
30
07
ON
ON
ON
X
ON
53
14.5
Mode 4 (Full Power) at
+3.3 VDC
X
1
20
07
ON
ON
ON
X
ON
67
17
Mode
(1)
Regulator
Control
Register
(0x0B)
Transmitter
Receiver
SYS_CLK
(13.56
MHz)
SYS_CLK
(60 kHz)
VDD_X
Typical
Current
(mA)
Typical
Power
Out
(dBm)
X = Don't care
Table 6-4. 5-V Operation Power Modes (1)
EN2
EN
Chip
Status
Control
Register
(0x00)
Power Down
0
0
XX
XX
OFF
OFF
OFF
OFF
OFF
<0.001
-
Sleep Mode
1
0
XX
XX
OFF
OFF
OFF
ON
ON
0.120
-
Standby Mode at
+5 VDC
X
1
81
07
OFF
OFF
ON
X
ON
3
-
Mode 1 at +5 VDC
X
1
01
07
OFF
OFF
ON
X
ON
5
-
Mode 2 at +5 VDC
X
1
03
07
OFF
ON
ON
X
ON
10.5
-
Mode 3 (Half Power) at
+5 VDC
X
1
31
07
ON
ON
ON
X
ON
70
20
Mode 4 (Full Power) at
+5 VDC
X
1
21
07
ON
ON
ON
X
ON
130
23
Mode
(1)
Regulator
Control
Register
(0x0B)
Transmitter
Receiver
SYS_CLK
(13.56
MHz)
SYS_CLK
(60 kHz)
VDD_X
Typical
Current
(mA)
Typical
Power
Out
(dBm)
X = Don't care
Table 6-3 and Table 6-4 show the configuration for the different power modes when using a 3.3-V or 5-V
system supply, respectively. The main reader enable signal is pin EN. When EN is set high, all of the
reader regulators are enabled, the 13.56-MHz oscillator is running and the SYS_CLK (output clock for
external micro controller) is also available.
The input pin EN2 has two functions:
• A direct connection from EN2 to VIN to ensure the availability of the regulated supply VDD_X and an
auxiliary clock signal (60 kHz, SYS_CLK) for an external MCU. This mode (EN = 0, EN2 = 1) is
intended for systems in which the MCU is also being supplied by the reader supply regulator (VDD_X)
and the MCU clock is supplied by the SYS_CLK output of the reader. This allows the MCU supply and
clock to be available during sleep mode.
• EN2 enables the start-up of the reader system from complete power down (EN = 0, EN2 = 0). In this
case the EN input is being controlled by the MCU (or other system device) that is without supply
voltage during complete power down (thus unable to control the EN input). A rising edge applied to the
EN2 input (which has an approximately 1-V threshold level) starts the reader supply system and 13.56MHz oscillator (identical to condition EN = 1).
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When user MCU is controlling EN and EN2, a delay of 1 ms between EN and EN2 must be used. If the
MCU controls only EN, EN2 is recommended to be connected to either VIN or GND, depending on the
application MCU requirements for VDD_X and SYS_CLK.
VIN
2 ms
SS
EN2
EN
5 ms
6 ms
Figure 6-3. Nominal Start-Up Sequence Using SPI With SS (MCU Controls EN2)
VIN
5 ms
EN2
6 ms
EN
Figure 6-4. Nominal Start-Up Sequence Using Parallel (MCU Controls EN2)
This start-up mode lasts until all of the regulators have settled and the 13.56-MHz oscillator has stabilized.
If the EN input is set high (EN = 1) by the MCU (or other system device), the reader stays active. If the EN
input is not set high (EN = 0) within 100 µs after the SYS_CLK output is switched from auxiliary clock (60
kHz) to high-frequency clock (derived from the crystal oscillator), the reader system returns to complete
Power-Down Mode 1. This option can be used to wake-up the reader system from complete Power Down
(PD Mode 1) by using a pushbutton switch or by sending a single pulse.
After the reader EN line is high, the other power modes are selected by control bits within the chip status
control register (0x00). The power mode options and states are listed in Table 6-3.
When EN is set high (or on rising edge of EN2 and then confirmed by EN = 1) the supply regulators are
activated and the 13.56-MHz oscillator started. When the supplies are settled and the oscillator frequency
is stable, the SYS_CLK output is switched from the auxiliary frequency of 60 kHz to the 13.56-MHz
frequency derived from the crystal oscillator. At this point, the reader is ready to communicate and perform
the required tasks. The MCU can then program the chip status control register 0x00 and select the
operation mode by programming the additional registers.
• Stand-by Mode (bit 7 = 1 of register 0x00), the reader is capable of recovering to full operation in
100 µs.
• Mode 1 (active mode with RF output disabled, bit 5 = 0 and bit 1 = 0 of register 0x00) is a low power
mode which allows the reader to recover to full operation within 25 µs.
• Mode 2 (active mode with only the RF receiver active, bit 1 = 1 of register 0x00) can be used to
measure the external RF field (as described in RSSI measurements paragraph) if reader-to-reader
anticollision is implemented.
• Modes 3 and 4 (active modes with the entire RF section active, bit 5 = 1 of register 0x00) are the
normal modes used for normal transmit and receive operations.
20
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6.4
6.4.1
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Receiver – Analog Section
Main and Auxiliary Receivers
The TRF7970A has two receiver inputs: RX_IN1 (pin 8) and RX_IN2 (pin 9). Each of the input is
connected to an external capacitive voltage divider to ensure that the modulated signal from the tag is
available on at least one of the two inputs. This architecture eliminates any possible communication holes
that may occur from the tag to the reader.
The two RX inputs (RX_IN1 and RX_IN2) are multiplexed into two receivers - the main receiver and the
auxiliary receiver. Only the main receiver is used for reception, the auxiliary receiver is used for signal
quality monitoring. Receiver input multiplexing is controlled by bit B3 in the Chip Status Control register
(address 0x00).
After startup, RX_IN1 is multiplexed to the main receiver which is composed of an RF envelope detection,
first gain and band-pass filtering stage, second gain and filtering stage with AGC. Only the main receiver
is connected to the digitizing stage which output is connected to the digital processing block. The main
receiver also has an RSSI measuring stage, which measures the strength of the demodulated signal
(subcarrier signal).
The primary function of the auxiliary receiver is to monitor the RX signal quality by measuring the RSSI of
the demodulated subcarrier signal (internal RSSI). After startup, RX_IN2 is multiplexed to the auxiliary
receiver. The auxiliary receiver has an RF envelope detection stage, first gain and filtering with AGC stage
and finally the auxiliary RSSI block.
The default MUX setting is RX_IN1 connected to the main receiver and RX_IN2 connected to the auxiliary
receiver. To determine the signal quality, the response from the tag is detected by the "main" (pin RX_IN1)
and "auxiliary" (pin RX_IN2) RSSI. Both values measured and stored in the RSSI level register (address
0x0F). The MCU can read the RSSI values from the TRF7970A RSSI register and make the decision if
swapping the input- signals is preferable or not. Setting B3 in Chip Status Control register (address 0x00)
to 1 connects RX_IN1 (pin 8) to the auxiliary received and RX_IN2 (pin 9) to the main receiver. This
mechanism needs to be used to avoid reading holes.
The main and auxiliary receiver input stages are RF envelope detectors. The RF amplitude at RX_IN1 and
RX_IN2 should be approximately 3 VPP for a VINsupply level greater than 3.3 V. If the VIN level is lower,
the RF input peak-to-peak voltage level should not exceed the VINlevel.
6.4.2
Receiver Gain and Filter Stages
The first gain and filtering stage has a nominal gain of 15 dB with an adjustable band-pass filter. The
band-pass filter has programmable 3d-B corner frequencies between 110 kHz to 450 kHz for the highpass filter and 570 kHz to 1500 kHz for the low-pass filter. After the band-pass filter, there is another gainand-filtering stage with a nominal gain of 8 dB and with frequency characteristics identical to the first bandpass stage.
The internal filters are configured automatically depending on the selected ISO communication standard in
the ISO Control register (address 0x01). If required, additional fine tuning can be done by writing directly
to the RX special setting registers (address 0x0A).
The main receiver also has a second receiver gain and digitizer stage which is included in the AGC loop.
The AGC loop is activated by setting the bit B2 = 1 in the Chip Status Control register (0x00). When
activated, the AGC continuously monitors the input signal level. If the signal level is significantly higher
than an internal threshold level, gain reduction is activated.
By default, the AGC window comparator is set after the first 4 pulses of the subcarrier signal. This
prevents the AGC from interfering with the reception of the remaining data packet. In certain situations,
this AGC freeze is not optimal, so it can be removed by setting B0 = 1 in the RX special setting register
(address 0x0A).
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Table 6-5. RX Special Setting Register (0x0A)
Function: Sets the gains and filters directly
Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register 0x01. When bits B7, B6, B5 and B4 are all zero, the
filters are set for ISO14443B (240 kHz to 1.4 MHz).
Bit
Name
B7
C212
Bandpass 110 kHz to 570 kHz
Appropriate for 212-kHz subcarrier system (FeliCa)
B6
C424
Bandpass 200 kHz to 900 kHz
Appropriate for 424-kHz subcarrier used in ISO15693
B5
M848
Bandpass 450 kHz to 1.5 MHz
Appropriate for Manchester-coded 848-kHz subcarrier used in ISO14443A
and B
B4
hbt
Bandpass 100 kHz to 1.5 MHz
Gain reduced for 18 dB
Appropriate for highest bit rate (848 kbps) used in high-bit-rate ISO14443
B3
gd1
B2
gd2
00
01
10
11
Sets the RX gain reduction, and reduces sensitivity
B1
B0
agcr
no-lim
Function
= Gain
= Gain
= Gain
= Gain
reduction
reduction
reduction
reduction
Description
0 dB
for 5 dB
for 10 dB
for 15 dB
AGC activation level change
AGC activation level changed from five times the digitizing level to three
times the digitizing level.
1 = 3x
0 = 5x
AGC action is not limited in time
AGC action can be done any time during receive process. It is not limited
to the start of receive ("max hold").
1 = continuously – no time limit
0 = 8 subcarrier pulses
Table 6-5 shows the various settings for the receiver analog section. It is important to note that setting B4,
B5, B6, and B7 to 0 results to a band-pass characteristic of 240 kHz to 1.4 MHz, which is appropriate for
ISO14443B 106 kbps, ISO14443A/B data-rates of 212 kbps and 424 kbps and FeliCa 424 kbps.
6.5
Receiver – Digital Section
The output of the TRF7970A analog receiver block is a digitized subcarrier signal and is the input to the
digital receiver block. This block includes a Protocol Bit Decoder section and the Framing Logic section.
The protocol bit decoders convert the subcarrier coded signal into a serial bit stream and a data clock.
The decoder logic is designed for maximum error tolerance. This enables the decoder section to
successfully decode even partly corrupted subcarrier signals that otherwise would be lost due to noise or
interference.
In the framing logic section, the serial bit stream data is formatted in bytes. Special signals such as the
start of frame (SOF), end of frame (EOF), start of communication, and end of communication are
automatically removed. The parity bits and CRC bytes are also checked and removed. This "clean" data is
then sent to the
127-byte FIFO register where it can be read by the external microcontroller system. Providing the data this
way, in conjunction with the timing register settings of the TRF7970A means the firmware developer has
to know about much less of the finer details of the ISO protocols to create a very robust application,
especially in low cost platforms where code space is at a premium and high performance is still required.
The start of the receive operation (successfully received SOF) sets the IRQ-flags in the IRQ and Status
register (0x0C). The end of the receive operation is signaled to the external system MCU by setting pin 13
(IRQ) to high. When data is received in the FIFO, an interrupt is sent to the MCU to signal that there is
data to be read from the FIFO. The FIFO status register (0x1C) should be used to provide the number of
bytes that should be clocked out during the actual FIFO read.
Any error in the data format, parity, or CRC is detected and notified to the external system by an interruptrequest pulse. The source condition of the interrupt request pulse is available in the IRQ status register
(0x0C). The main register controlling the digital part of the receiver is the ISO Control register (0x01). By
writing to this register, the user selects the protocol to be used. With each new write in this register, the
default presets are reloaded in all related registers, so no further adjustments in other registers are
needed for proper operation.
22
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NOTE
If register setting changes are needed for fine tuning the system, they must be done after
setting the ISO Control register (0x01).
The framing section also supports the bit-collision detection as specified in ISO14443A. When a bit
collision is detected, an interrupt request is sent and a flag is set in the IRQ and Status register (0x0C).
The position of the bit collision is written in two registers: Collision Position register (0x0E) and partly in
Collision Position and Interrupt Mask register (0x0D) (bits B6 and B7).
The collision position is presented as sequential bit number, where the count starts immediately after the
start bit. This means a collision in the first bit of a UID would give the value 00 0001 0000 in these
registers when their contents are combined after being read. (the count starts with 0 and the first 16 bits
are the command code and the Number of Valid Bits (NVB) byte).
The receive section also contains two timers. The RX wait time timer is controlled by the value in the RX
Wait Time register (0x08). This timer defines the time interval after the end of the transmit operation in
which the receive decoders are not active (held in reset state). This prevents false detections resulting
from transients following the transmit operation. The value of the RX Wait Time register (0x08) defines the
time in increments of 9.44 µs. This register is preset at every write to ISO Control register (0x01)
according to the minimum tag response time defined by each standard.
The RX no response timer is controlled by the RX No Response Wait Time register (0x07). This timer
measures the time from the start of slot in the anticollision sequence until the start of tag response. If there
is no tag response in the defined time, an interrupt request is sent and a flag is set in the IRQ Status
register (0x0C). This enables the external controller to be relieved of the task of detecting empty slots. The
wait time is stored in the register in increments of 37.76 µs. This register is also preset, automatically for
every new protocol selection.
The digitized output of the analog receiver is at the input of the digital portion of the receiver. This input
signal is the subcarrier coded signal, which is a digital representation of modulation signal on the RF
envelope.
The digital part of the receiver consists of two sections which partly overlap. The first section contains the
bit decoders for the various protocols. The bit decoders convert the subcarrier coded signal to a bit stream
and also the data clock. Thus the subcarrier coded signal is transformed to serial data and the data clock
is extracted. The decoder logic is designed for maximum error tolerance. This enables the decoders to
successfully decode even partly corrupted (due to noise or interference) subcarrier signals.
The second section contains the framing logic for the protocols supported by the bit decoder section. In
the framing section, the serial bit stream data is formatted in bytes. In this process, special signals like the
SOF (start of frame), EOF (end of frame), start of communication, end of communication are automatically
removed. The parity bits and CRC bytes are checked and also removed. The end result is "clean or raw"
data which is sent to the
127-byte FIFO register where it can be read out by the external microcontroller system.
The start of the receive operation (successfully received SOF) sets the flags in the IRQ and Status
register. The end of the receive operation is signaled to the external system (MCU) by sending an interrupt
request (pin 13 IRQ). If the receive data packet is longer than 96 bytes, an interrupt is sent to the MCU
when the received data occupies 75% of the FIFO capacity to signal that the data should be removed
from the FIFO.
Any error in data format, parity or CRC is detected and the external system is made aware of the error by
an interrupt request pulse. The nature of the interrupt request pulse is available in the IRQ and Status
register (address 0x0C). The bit coding description of this register is shown in Section 6.14.3.3.1. The
information in IRQ and Status register differs if the chip is configured as RFID reader or as NFC device
(including tag emulation). The case of NFC operation is presented in Section 6.12.
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The main register controlling the digital part of the receiver is the ISO Control register (address 0x01). By
writing to this register, the user selects the protocol to be used. At the same time (with each new write in
this register) the default preset in all related registers is done, so no further adjustments in other registers
are needed for proper operation. Table 6-6 shows the coding of the ISO Control register (0x01).
Table 6-6. Coding of the ISO Control Register
Bit
Signal Name
B7
rx_crc_n
Function
Comments
1 = No RX CRC
Receiving without CRC
0 = RX CRC
B6
dir_mode
0 = output is subcarrier data
Direct mode type
1 = output is bit stream and clock from decoder selected by ISO bits
B5
rfid
0 = RFID reader mode
RFID mode
1 = NFC or Card Emulator mode
RFID: Mode selection
B4
iso_4
NFC:
RFID protocol, NFC target
0 = NFC target
1 = NFC initiator
RFID: Mode selection (see Table 6-7)
B3
iso_3
NFC:
RFID protocol, NFC mode
0 = passive mode
1 = active mode
RFID: Mode selection
B2
iso_2
RFID protocol, Card Emulation
NFC:
0 = NFC normal modes
1 = Card Emulation mode
B1
iso_1
RFID protocol, NFC bit rate
RFID: Mode selection
NFC: Bit rate selection or Card Emulation selection (see Table 6-8)
B0
iso_0
RFID protocol, NFC bit rate
RFID: Mode selection
NFC: Bit rate selection or Card Emulation selection (see Table 6-8)
Table 6-7. Coding of the ISO Control Register For RFID Mode (B5 = 0)
Iso_4
Iso_3
Iso_2
Iso_1
Iso_0
0
0
0
0
0
ISO15693 low bit rate, one subcarrier, 1 out of 4
0
0
0
0
1
ISO15693 low bit rate, one subcarrier, 1 out of 256
0
0
0
1
0
ISO15693 high bit rate, one subcarrier, 1 out of 4
0
0
0
1
1
ISO15693 high bit rate, one subcarrier, 1 out of 256
0
0
1
0
0
ISO15693 low bit rate, double subcarrier, 1 out of 4
0
0
1
0
1
ISO15693 low bit rate, double subcarrier, 1 out of 256
0
0
1
1
0
ISO15693 high bit rate, double subcarrier, 1 out of 4
0
0
1
1
1
ISO15693 high bit rate, double subcarrier, 1 out of 256
0
1
0
0
0
ISO14443A, bit rate 106 kbps
0
1
0
0
1
ISO14443 A high bit rate 212 kbps
24
Protocol
Detailed Description
Remarks
Default for RFID IC
RX bit rate when TX rate
different from RX rate (see
register 0x03)
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Table 6-7. Coding of the ISO Control Register For RFID Mode (B5 = 0) (continued)
Iso_4
Iso_3
Iso_2
Iso_1
Iso_0
0
1
0
1
0
ISO14443 A high bit rate 424 kbps
Protocol
0
1
0
1
1
ISO14443 A high bit rate 848 kbps
0
1
1
0
0
ISO14443B, bit rate 106 kbps
0
1
1
0
1
ISO14443 B high bit rate 212 kbps
0
1
1
1
0
ISO14443 B high bit rate 424 kbps
0
1
1
1
1
ISO14443 B high bit rate 848 kbps
1
0
0
1
1
Reserved
1
0
1
0
0
Reserved
1
1
0
1
0
FeliCa 212 kbps
1
1
0
1
1
FeliCa 424 kbps
Remarks
RX bit rate when TX rate
different from RX rate (see
register 0x03)
Table 6-8. Coding of the ISO Control Register For NFC
Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1,
B2 = 1)
6.5.1
NFC (B5 = 1, B2 = 0)
Card Emulation
(B5 = 1, B2 = 1)
0
N/A
ISO14443A
1
106 kbps
ISO14443B
1
0
212 kbps
N/A
1
1
424 kbps
N/A
Iso_1
Iso_0
0
0
Received Signal Strength Indicator (RSSI)
The TRF7970A incorporates in total three independent RSSI building blocks: Internal Main RSSI, Internal
Auxiliary RSSI, and External RSSI. The internal RSSI blocks are measuring the amplitude of the
subcarrier signal; the External RSSI block measures the amplitude of the RF carrier signal at the receiver
input.
6.5.1.1
Internal RSSI – Main and Auxiliary Receivers
Each receiver path has its own RSSI block to measure the envelope of the demodulated RF signal
(subcarrier). Internal Main RSSI and Internal Auxiliary RSSI are identical however connected to different
RF input pins. The Internal RSSI is intended for diagnostic purposes to set the correct RX path conditions.
The Internal RSSI values can be used to adjust the RX gain settings or decide which RX path (Main or
Auxiliary) provides the greater amplitude and hence to decide if the MUX may need to be reprogrammed
to swap the RX input signal. The measuring system latches the peak value, so the RSSI level can be read
after the end of each receive packet. The RSSI register values are reset with every transmission (TX) by
the reader. This ensures an updated RSSI measurement for each new tag response.
The Internal RSSI has 7 steps (3 bit) with a typical increment of approximately 4 dB. The operating range
is between 600 mVPP and 4.2 VPP with a typical step size of approximately 600 mV. Both Internal Main
and Internal Auxiliary RSSI values are stored in the RSSI Levels and Oscillator Status register (0x0F). The
nominal relationship between the input RF peak level and the RSSI value is shown in Figure 6-5.
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7
6
5
4
3
2
1
0
0
0.25
0.5
0.75
1
1.25
1.5 1.75
2
2.25 2.5 2.75
Input RF Carrier Level in VPP [V]
3
3.25
3.5
3.75
4
4.25
Figure 6-5. Digital Internal RSSI (Main and Auxiliary) Value vs RF Input Level in VPP (V)
This RSSI measurement is done during the communication to the Tag; this means the TX must be on. Bit
1 in the Chip Status Control register (0x00) defines if Internal RSSI or the External RSSI value is stored in
the RSSI Levels and Oscillator Status register (0x0F). Direct command 0x18 is used to trigger an Internal
RSSI measurement.
6.5.1.2
External RSSI
RSSI Levels and Oscillator Status Register value (0x0F)
The External RSSI is mainly used for test and diagnostic to sense the amplitude of any 13.56-MHz signal
at the receivers RX_IN1 input. The External RSSI measurement is typically done in active mode when the
receiver is on but transmitter output is off. The level of the RF signal received at the antenna is measured
and stored in the RSSI Levels and Oscillator Status register 0x0F. The relationship between the voltage at
the RX_IN1 input and the 3-bit code is shown in Figure 6-6.
7
6
5
4
3
2
1
0
0
25
50
75
100
125
150
175
200
225
250
275
300
325
RF Input Voltage Level at RF_IN1 in mVPP
Figure 6-6. Digital External RSSI Value vs RF Input Level in VPP (mV)
26
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The relation between the 3-bit code and the external RF field strength (A/m) sensed by the antenna must
be determined by calculation or by experiments for each antenna design. The antenna Q-factor and
connection to the RF input influence the result. Direct command 0x19 is used to trigger an Internal RSSI
measurement.
For clarity, to check the internal or external RSSI value independent of any other operation, the user must:
1. Set transmitter to desired state (on or off) using Bit 5 of Chip Status Control register (0x00) and enable
receiver using Bit 1.
2. Check internal or external RSSI using direct commands 0x18 or 0x19, respectively. This action places
the RSSI value in the RSSI register.
3. Delay at least 50 µs.
4. Read the RSSI register using direct command 0x0F; values range from 0x40 to 0x7F.
5. Repeat steps 1-4 as desired, as register is reset after it is read.
6.6
Oscillator Section
The 13.56-MHz or 27.12-MHz crystal (or oscillator) is controlled by the Chip Status Control register (0x00)
and the EN and EN2 terminals. The oscillator generates the RF frequency for the RF output stage as well
as the clock source for the digital section. The buffered clock signal is available at pin 27 (SYS_CLK) for
any other external circuits. B4 and B5 inside the Modulation and SYS_CLK register (0x09) can be used to
divide the external SYS_CLK signal at pin 27 by 1, 2 or 4.
Typical start-up time from complete power down is in the range of 3.5 ms.
During Power Down Mode 2 (EN = 0, EN2 = 1) the frequency of SYS_CLK is switched to 60 kHz (typical).
The crystal needs to be connected between pin 30 and pin 31. The external shunt capacitors values for C1
and C2 must be calculated based on the specified load capacitance of the crystal being used. The external
shunt capacitors are calculated as two identical capacitors in series plus the stray capacitance of the
TRF7970A and parasitic PCB capacitance in parallel to the crystal.
The parasitic capacitance (CS, stray and parasitic PCB capacitance) can be estimated at 4 to 5 pF
(typical).
As an example, using a crystal with a required load capacitance (CL) of 18 pF, the calculation is shown in
Equation 1.
C1 = C2 = 2 × (CL– CS) = 2 × (18 pF – 4.5 pF) = 27 pF
(1)
A 27-pF capacitor must be placed on pins 30 and 31 to ensure proper crystal oscillator operation.
CS
TRF7970A
Pin 30
Pin 31
Crystal
C1
C2
Figure 6-7. Crystal Block Diagram
Any crystal used with TRF7970A should have minimum characteristics shown in Table 6-9.
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Table 6-9. Minimum Crystal Requirements
Parameter
Specification
Frequency
13.56 MHz or 27.12 MHz
Mode of Operation
Fundamental
Type of Resonance
Parallel
Frequency Tolerance
±20 ppm
Aging
< 5 ppm/year
Operation Temperature Range
-40°C to 85°C
Equivalent Series Resistance
50 Ω
As an alternative, an external clock oscillator source can be connected to Pin 31 to provide the system
clock; pin 30 can be left open.
6.7
Transmitter – Analog Section
The 13.56-MHz oscillator generates the RF signal for the PA stage. The power amplifier consists of a
driver with selectable output resistance of nominal 4 Ω or 8 Ω. The transmit power level is set by bit B4 in
the Chip Status Control register (0x00). The transmit power levels are selectable between 100 mW (half
power) or 200 mW (full power) when configured for 5-V automatic operation. The transmit power levels
are selectable between 33 mW (half power) or 70 mW (full power) when configured for 3-V automatic
operation.
The ASK modulation depth is controlled by bits B0, B1, and B2 in the Modulator and SYS_CLK Control
register (0x09). The ASK modulation depth range can be adjusted between 7% to 30% or 100% (OOK).
External control of the transmit modulation depth is possible by setting the ISO Control register (0x01) to
direct mode. While operating the TRF7970A in direct mode, the transmit modulation is made possible by
selecting the modulation type ASK or OOK at pin 12. External control of the modulation type is made
possible only if enabled by setting B6 in the Modulator and SYS_CLK Control register (0x09) to 1.
In normal operation mode, the length of the modulation pulse is defined by the protocol selected in the
ISO Control register (0x01). With a high-Q antenna, the modulation pulse is typically prolonged, and the
tag detects a longer pulse than intended. For such cases, the modulation pulse length needs to be
corrected by using the TX Pulse Length Control register (0x06).
If the register contains all zeros, then the pulse length is governed by the protocol selection. If the register
contains a value other than 0x00, the pulse length is equal to the value of the register multiplied by
73.7 ns; therefore, the pulse length can be adjusted between 73.7 ns and 18.8 µs in 73.7-ns increments.
6.8
Transmitter – Digital Section
The digital part of the transmitter is a mirror of the receiver. The settings controlled the ISO Control
register (0x01) are applied to the transmitter just like the receiver. In the TRF7970A default mode the
TRF7970A automatically adds these special signals: start of communication, end of communication, SOF,
EOF, parity bits, and CRC bytes.
The data is then coded to modulation pulse levels and sent to the RF output stage modulation control unit.
Similar to working with the receiver, this means that the external system MCU only has to load the FIFO
with data and all the microcoding is done automatically, again saving the firmware developer code space
and time. Additionally, all of the registers used for transmit parameter control are automatically preset to
optimum values when a new selection is entered into the ISO Control register (0x01).
Note: FIFO must be reset before starting any transmission with Direct Command 0x0F.
There are two ways to start the transmit operation:
• Load the number of bytes to be sent into registers 0x1D and 0x1E and load the data to be sent into the
FIFO (address 0x1F), followed by sending a transmit command (see Direct Commands section). The
transmission then starts when the transmit command is received.
28
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Send the transmit command and the number of bytes to be transmitted first, and then start to send the
data to the FIFO. The transmission starts when first data byte is written into the FIFO.
NOTE
If the data length is longer than the FIFO, the TRF7970A notifies the external system MCU
when most of the data from the FIFO has been transmitted by sending an interrupt request
with a flag in the IRQ register to indicate a FIFO low or high status. The external system
should respond by loading the next data packet into the FIFO.
At the end of a transmit operation, the external system MCU is notified by interrupt request (IRQ) with a
flag in IRQ register (0x0C) indicating TX is complete (example value = 0x80).
The TX Length registers also support incomplete byte transmission. The high two nibbles in register 0x1D
and the nibble composed of bits B4 through B7 in register 0x1E store the number of complete bytes to be
transmitted. Bit B0 in register 0x1E is a flag indicating that there are also additional bits to be transmitted
that do not form a complete byte. The number of bits is stored in bits B1 through B3 of the same register
(0x1E).
Some protocols have options, and there are two sublevel configuration registers to select the TX protocol
options.
• ISO14443B TX Options register (0x02). This register controls the SOF and EOF selection and EGT
selection for the ISO14443B protocol.
• ISO14443A High Bit Rate Options and Parity register (0x03). This register enables the use of different
bit rates for RX and TX operations in the ISO14443 high bit rate protocol and also selects the parity
method in the ISO14443A high bit rate protocol.
The digital section also has a timer. The timer can be used to start the transmit operation at a specified
time in accordance with a selected event.
6.9
Transmitter – External Power Amplifier and Subcarrier Detector
The TRF7970A can be used in conjunction with an external TX power amplifier or external subcarrier
detector for the receiver path. In this case, certain registers must be programmed as shown here:
• Bit B6 of the Regulator and I/O Control register (0x0B) must be set to 1. This setting has two functions:
first, to provide a modulated signal for the transmitter if needed, and second, to configure the
TRF7970A receiver inputs for an external demodulated subcarrier input.
• Bit B3 of the Modulation and SYS_CLK Control register (0x09) must be set to 1 (see
Section 6.14.3.2.8). This function configures the ASK/OOK pin for either a digital or analog output (B3
= 0 enables a digital output, B3 = 1 enables an analog output). The design of an external power
amplifier requires detailed RF knowledge. There are also readily designed and certified high-power HF
reader modules on the market.
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6.10 TRF7970A IC Communication Interface
6.10.1 General Introduction
The communication interface to the reader can be configured in two ways: with a eight line parallel
interface (D0:D7) plus DATA_CLK, or with a three or four wire Serial Peripheral Interface (SPI). The SPI
interface uses traditional Master Out/Slave In (MOSI), Master In/Slave Out (MISO), IRQ, and DATA_CLK
lines. The SPI can be operated with or without using the Slave Select line.
These communication modes are mutually exclusive; that is, only one mode can be used at a time in the
application.
When the SPI interface is selected, the unused I/O_2, I/O_1, and I/O_0 pins must be hard-wired as shown
in Table 6-10. At power up, the TRF7970A samples the status of these three pins and then enters one of
the possible SPI modes.
The TRF7970A always behaves as the slave device, and the microcontroller (MCU) behaves as the
master device. The MCU initiates all communications with the TRF7970A, and the TRF7970A makes use
of the Interrupt Request (IRQ) pin in both parallel and SPI modes to prompt the MCU for servicing
attention.
Table 6-10. Pin Assignment in Parallel and Serial Interface Connection or Direct Mode
(1)
(2)
(3)
(4)
(5)
30
Pin
Parallel
DATA_ CLK
DATA_CLK
Parallel (Direct Mode)
DATA_CLK
SPI Without SS (1)
SPI With SS
DATA_CLK from master
MOSI
(2)
= data in (reader in)
DATA_CLK from master
MOSI (2) = data in (reader in)
I/O_7
A/D[7]
(not used)
I/O_6
A/D[6]
Direct mode, data out (subcarrier
MISO (3) = data out (MCU out)
or bit stream)
MISO (3) = data out (MCU out)
I/O_5 (4)
A/D[5]
Direct mode, strobe – bit clock
out
See
See
I/O_4
A/D[4]
(not used)
SS – slave select (5)
(not used)
I/O_3
A/D[3]
(not used)
(not used)
(not used)
I/O_2
A/D[2]
(not used)
At VDD
At VDD
I/O_1
A/D[1]
(not used)
At VDD
At VSS
I/O_0
A/D[0]
(not used)
At VSS
At VSS
IRQ
IRQ interrupt
IRQ interrupt
IRQ interrupt
IRQ interrupt
(4)
(4)
FIFO is not accessible in SPI without SS mode. See device errata for detailed information.
MOSI = Master Out, Slave In
MISO = Master In, Slave Out
I/O_5 pin is used only for information when data is put out of the chip (for example, reading 1 byte from the chip). It is necessary first to
write in the address of the register (8 clocks) and then to generate another 8 clocks for reading out the data. The I/O_5 pin goes high
during the second 8 clocks. But for normal SPI operations, I/O_5 pin is not used.
Slave_Select pin is active low
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Communication is initialized by a start condition, which is expected to be followed by an
Address/Command word (Adr/Cmd). The Adr/Cmd word is 8 bits long, and Table 6-11 shows its format.
Table 6-11. Address and Command Word Bit Distribution
Bit
Description
Bit Function
Address
Command
B7
Command control bit
0 = address
1 = command
0
1
B6
Read/Write
0 = write
1 = read
R/W
0
B5
Continuous address mode
1 = Continuous mode
R/W
0
B4
Address/Command bit 4
Adr 4
Cmd 4
B3
Address/Command bit 3
Adr 3
Cmd 3
B2
Address/Command bit 2
Adr 2
Cmd 2
B1
Address/Command bit 1
Adr 1
Cmd 1
B0
Address/Command bit 0
Adr 0
Cmd 0
The MSB (bit 7) determines if the word is to be used as a command or as an address. The last two
columns of Table 6-11 show the function of the separate bits if either address or command is written. Data
is expected once the address word is sent. In continuous-address mode (Cont. mode = 1), the first data
that follows the address is written (or read) to (from) the given address. For each additional data, the
address is incremented by one. Continuous mode can be used to write to a block of control registers in a
single stream without changing the address; for example, setup of the predefined standard control
registers from the MCU non-volatile memory to the reader. In non-continuous address mode (simple
addressed mode), only one data word is expected after the address.
Address Mode is used to write or read the configuration registers or the FIFO. When writing more than 12
bytes to the FIFO, the Continuous Address Mode should be set to 1.
The Command Mode is used to enter a command resulting in reader action (for example, initialize
transmission, enable reader, and turn reader on or off).
Examples of expected communications between an MCU and the TRF7970A are shown in the following
sections.
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6.10.1.1 Continuous Address Mode
Table 6-12. Continuous Address Mode
Start
Adr x
Data(x)
Data(x+1)
Data(x+2)
Data(x+3)
Data(x+4)
...
Data(x+n)
StopCont
Figure 6-8. Continuous Address Register Write Example Starting with Register 0x00 Using SPI With SS
Figure 6-9. Continuous Address Register Read Example Starting with Register 0x00 Using SPI With SS
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6.10.1.2 Noncontinuous Address Mode (Single Address Mode)
Table 6-13. Noncontinuous Address Mode (Single Address Mode)
Start
Adr x
Data(x)
Adr y
Data(y)
...
Adr z
Data(z)
StopSgl
Figure 6-10. Single Address Register Write Example of Register 0x00 Using SPI With SS
Figure 6-11. Single Address Register Read Example of Register 0x00 Using SPI With SS
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6.10.1.3 Direct Command Mode
Table 6-14. Direct Command Mode
Start
Cmd x
(Optional data or command)
Stop
Figure 6-12. Direct Command Example of Sending 0x0F (Reset) Using SPI With SS
The other Direct Command Codes from MCU to TRF7970A IC are described in Section 6.13.
6.10.1.4 FIFO Operation
The FIFO is a 127-byte register at address 0x1F with byte storage locations 0 to 126. FIFO data is loaded
in a cyclical manner and can be cleared by a reset command (0x0F) (see Figure 6-12 showing this Direct
Command).
Associated with the FIFO are two counters and three FIFO status flags. The first counter is a 7-bit FIFO
byte counter (bits B0 to B6 in register 0x1C) that tracks the number of bytes loaded into the FIFO. If the
number of bytes in the FIFO is n, the register value is n (number of bytes in FIFO register). For example, if
8 bytes are in the FIFO, the FIFO counter (Register 0x1C) has the hexadecimal value of 0x08 (binary
value of 00001000).
A second counter (12 bits wide) indicates the number of bytes being transmitted (registers 0x1D and
0x1E) in a data frame. An extension to the transmission-byte counter is a 4-bit broken-byte counter also
provided in register 0x1E (bits B0 to B3). Together these counters make up the TX length value that
determines when the reader generates the EOF byte.
FIFO status flags are as follows:
• FIFO overflow (bit B7 of register 0x1C) – indicates that the FIFO has more than 127 bytes loaded
During transmission, the FIFO is checked for an almost-empty condition, and during reception for an
almost-full condition. The maximum number of bytes that can be loaded into the FIFO in a single
sequence is 127 bytes.
NOTE
The number of bytes in a frame, transmitted or received, can be greater than 127 bytes.
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During transmission, the MCU loads the TRF7970A IC's FIFO (or during reception the MCU removes data
from the FIFO), and the FIFO counter counts the number of bytes being loaded into the FIFO. Meanwhile,
the byte counter keeps track of the number of bytes being transmitted. An interrupt request is generated if
the number of bytes in the FIFO is less than 32 or greater than 96, so that MCU can send new data or
remove the data as necessary. The MCU also checks the number of data bytes to be sent, so as to not
surpass the value defined in TX length bytes. The MCU also signals the transmit logic when the last byte
of data is sent or was removed from the FIFO during reception. Transmission starts automatically after the
first byte is written into FIFO.
Figure 6-13. Example of Checking the FIFO Status Register Using SPI With SS
6.10.2 Parallel Interface Mode
In parallel mode, the start condition is generated on the rising edge of the I/O_7 pin while the CLK is high.
This is used to reset the interface logic. Figure 6-14 shows the sequence of the data, with an 8-bit address
word first, followed by data.
Communication is ended by:
• The StopSmpl condition, where a falling edge on the I/O_7 pin is expected while CLK is high.
• The StopCont condition, where the I/O_7 pin must have a successive rising and falling edge while CLK
is low to reset the parallel interface and be ready for the new communication sequence.
• The StopSmpl condition is also used to terminate the direct mode.
Figure 6-14. Parallel Interface Communication With Simple Stop Condition (StopSmpl)
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Figure 6-15. Parallel Interface Communication with Continuous Stop Condition (StopCont)
Figure 6-16. Example of Parallel Interface Communication With Continuous Stop Condition
6.10.3 Reception of Air Interface Data
At the start of a receive operation (when SOF is successfully detected), B6 is set in the IRQ Status
register. An RX complete interrupt request is sent to the MCU at the end of the receive operation if the
receive data string is shorter than or equal to the number of bytes configured in the Adjustable FIFO IRQ
Levels register (0x14). An IRQ_FIFO interrupt request is sent to the MCU during the receive operation if
the data string is greater than the level set in the Adjustable FIFO IRQ Levels register (0x14). After
receiving an IRQ_FIFO or RX complete interrupt, the MCU must read the FIFO status register (0x1C) to
determine the number of bytes to be read from the FIFO. Next, the MCU must read the data in the FIFO.
It is optional to read the FIFO status register (0x1C) after reading FIFO data to determine if the receive is
complete. In the case of an IRQ_FIFO, the MCU should expect either another IRQ_FIFO or RX complete
interrupt. This is repeated until an RX complete interrupt is generated. The MCU receives the interrupt
request, then checks to determine the reason for the interrupt by reading the IRQ Status register (0x0C),
after which the MCU reads the data from the FIFO.
If the reader detects a receive error, the corresponding error flag is set (framing error, CRC error) in the
IRQ Status register, indicating to the MCU that reception was not completed correctly.
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6.10.4 Data Transmission to MCU
Before beginning data transmission, the FIFO should always be cleared with a reset command (0x0F).
Data transmission is initiated with a selected command (see Section 6.13). The MCU then commands the
reader to do a continuous write command (0x3D) starting from register 0x1D. Data written into register
0x1D is the TX Length Byte 1 (upper and middle nibbles), while the following byte in register 0x1E is the
TX Length Byte 2 (lower nibble and broken byte length) (see Table 6-57 and Table 6-58) . Note that the
TX byte length determines when the reader sends the end of frame (EOF) byte. After the TX length bytes
are written, FIFO data is loaded in register 0x1F with byte storage locations 0 to 127. Data transmission
begins automatically after the first byte is written into the FIFO. The loading of TX length bytes and the
FIFO can be done with a continuous-write command, as the addresses are sequential.
At the start of transmission, the flag B7 (IRQ_TX) is set in the IRQ Status register, and at the end of the
transmit operation, an interrupt is sent to inform the MCU that the task is complete.
6.10.5 Serial Interface Communication (SPI)
When an SPI interface is used, I/O pins I/O_2, I/O_1, and I/O_0 must be hard wired according to Table 610. On power up, the TRF7970A looks for the status of these pins and then enters into the corresponding
mode.
The choice of one of these modes over another should be predicated by the available GPIOs and the
desired control of the system.
The serial communications work in the same manner as the parallel communications with respect to the
FIFO, except for the following condition. On receiving an IRQ from the reader, the MCU reads the
TRF7970A IRQ Status register to determine how to service the reader. After this, the MCU must to do a
dummy read to clear the reader's IRQ status register. The dummy read is required in SPI mode because
the reader's IRQ status register needs an additional clock cycle to clear the register. This is not required in
parallel mode because the additional clock cycle is included in the Stop condition. When first establishing
communications with the TRF7970A, the SOFT_INIT (0x03) and IDLE (0x00) commands should be sent
first from the MCU (see Table 6-19).
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The procedure for a dummy read is as follows:
1. Start the dummy read:
(a) When using slave select (SS): set SS bit low.
(b) When not using SS: start condition is when Data Clock is high (see Table 6-10).
2. Send address word to IRQ status register (0x0C) with read and continuous address mode bits set to 1
(see Table 6-10).
3. Read 1 byte (8 bits) from IRQ status register (0x0C).
4. Dummy-read 1 byte from register 0x0D (collision position and interrupt mask).
5. Stop the dummy read:
(a) When using slave select (SS): set SS bit high.
(b) When not using SS: stop condition when Data Clock is high.
Read Data in
IRQ Status Register
Write Address
Byte (0x6C)
Dummy Read
DATA _CLK
MOSI
B7
MISO
B6
B5
B4
B3
Don’t Care
B2
B1
B0
No Data Transitions (All High or Low)
B7
B6
B5
B4
B3
B2
B1
No Data Transitions (All High or Low)
B0
Ignore
SLAVE
SELECT
Figure 6-17. Procedure for Dummy Read
Figure 6-18. Example of Dummy Read Using SPI With SS
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6.10.5.1 Serial Interface Mode With Slave Select (SS)
The serial interface is in reset while the Slave Select signal is high. Serial data in (MOSI) changes on the
rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19. Communication is
terminated when the Slave Select signal goes high.
All words must be 8 bits long with the MSB transmitted first.
tSTE,LEAD
Slave
Select
WRITE
READ
MOSI Transitions on Data Clock
Rising Edge
MOSI Valid on Data Clock Falling Edge
Data Transition is on Data Clock
Rising Edge
MISO Valid on Data Clock Falling Edge
tSTE,LAG
1/fUCxCLK
tSTE,DIS
DATA
CLK
tLO/HI
MOSI
tLO/HI
tSU,SI
b7
b6…b1
tHD,SI
NO DATA TRANSITIONS
(ALL HIGH/LOW)
b0
tSU,SO tHD,SO
MISO
DON’T CARE
tVALID,SO
b7
b6...b1
b0
Figure 6-19. SPI With Slave Select Timing Diagram
The read command is sent out on the MOSI pin, MSB first, in the first eight clock cycles. MOSI data
changes on the rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19.
During the write cycle, the serial data out (MISO) is not valid. After the last read command bit (B0) is
validated at the eighth falling edge of SCLK, valid data can be read on the MISO pin at the falling edge of
SCLK. It takes eight clock edges to read out the full byte (MSB first). See Section 5.3 for electrical
specifications related to Figure 6-19.
The continuous read operation is shown in Figure 6-20.
WRITE
ADDRESS BYTE
READ DATA
BYTE 1
READ DATA
BYTE n
No Data Transitions (All High or Low)
No Data Transitions (All High or Low)
B7
B7
DATA
CLK
MOSI
MISO
B7
B6
B5
B4
B3
B2
B1
B0
DON’T CARE
B6
B5
B4
B3
B2
B1
B0
B6
B5
B4
B3
B2
B1
B0
SLAVE
SELECT
Figure 6-20. Continuous Read Operation Using SPI With Slave Select
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Figure 6-21. Continuous Read of Registers 0x00 Through 0x05 Using SPI With SS
Performing Single Slot Inventory Command as an example is shown in Figure 6-22. Reader registers (in
this example) are configured for 5 VDC in and default operation.
Figure 6-22. Inventory Command Sent From MCU to TRF7970A
The TRF7970A takes these bytes from the MCU and then send out Request Flags, Inventory Command
,and Mask over the air to the ISO15693 transponder. After these three bytes have been transmitted, an
interrupt occurs to indicate back to the reader that the transmission has been completed. In the example in
Figure 6-23, this IRQ occurs approximately 1.6 ms after the SS line goes high after the Inventory
command is sent out.
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Figure 6-23. IRQ After Inventory Command
The IRQ status register read (0x6C) yields 0x80, which indicates that TX is indeed complete. This is
followed by a dummy clock. Then, if a tag is in the field and no error is detected by the reader, a second
interrupt is expected and occurs (in this example) approximately 4 ms after first IRQ is read and cleared.
In the continuation of the example (see Figure 6-24), the IRQ Status Register is read using method
previously recommended, followed by a single read of the FIFO status register, which indicates that there
are 10 bytes to be read out.
Figure 6-24. Read IRQ Status Register After Inventory Command
This is then followed by a continuous read of the FIFO. The first byte is (and should be) 0x00 for no error.
The next byte is the DSFID (usually shipped by manufacturer as 0x00), then the UID, shown here up to
the next most significant byte, the MFG code (shown as 0x07 (TI silicon)).
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Figure 6-25. Continuous Read of FIFO After Inventory Command
At this point, it is good form to reset the FIFO and then read out the RSSI value of the tag. In this case the
transponder is very close to the antenna, so value of 0x7F is recovered.
Figure 6-26. Reset FIFO and Read RSSI
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6.10.6 Direct Mode
Direct mode allows the user to configure the reader in one of two ways. Direct Mode 0 (bit 6 = 0, as
defined in ISO Control register) allows the user to use only the front-end functions of the reader,
bypassing the protocol implementation in the reader. For transmit functions, the user has direct access to
the transmit modulator through the MOD pin (pin 14). On the receive side, the user has direct access to
the subcarrier signal (digitized RF envelope signal) on I/O_6 (pin 23).
Direct Mode 1 (bit 6 = 1, as defined in ISO Control register) uses the subcarrier signal decoder of the
selected protocol (as defined in ISO Control register). This means that the receive output is not the
subcarrier signal but the decoded serial bit stream and bit clock signals. The serial data is available on
I/O_6 (pin 23) and the bit clock is available on I/O_5 (pin 22). The transmit side is identical; the user has
direct control over the RF modulation through the MOD input. This mode is provided so that the user can
implement a protocol that has the same bit coding as one of the protocols implemented in the reader, but
needs a different framing format.
To select direct mode, the user must first choose which direct mode to enter by writing B6 in the ISO
Control register. This bit determines if the receive output is the direct subcarrier signal (B6 = 0) or the
serial data of the selected decoder. If B6 = 1, then the user must also define which protocol should be
used for bit decoding by writing the appropriate setting in the ISO Control register.
The reader actually enters the direct mode when B6 (direct) is set to 1 in the chip status control register.
Direct mode starts immediately. The write command should not be terminated with a stop condition (see
communication protocol), because the stop condition terminates the direct mode and clears B6. This is
necessary as the direct mode uses one or two I/O pins (I/O_6, I/O_5). Normal parallel communication is
not possible in direct mode. Sending a stop condition terminates direct mode.
Figure 6-27 shows the different configurations available in direct mode.
• In mode 0, the reader is used as an AFE only, and protocol handling is bypassed.
• In mode 1, framing is not done, but SOF and EOF are present. This allows for a user-selectable
framing level based on an existing ISO standard.
• In mode 2, data is ISO-standard formatted. SOF, EOF, and error checking are removed, so the
microprocessor receives only bytes of raw data through a 127-byte FIFO.
Analog Front End (AFE)
Direct Mode 0:
Raw RF Sub-Carrier
Data Stream
ISO Encoders/Decoders
14443A
14443B
15693
FeliCa
Direct Mode 1:
Raw Digital ISO Coded
Data Without
Protocol Frame
Packetization/Framing
Microcontroller
ISO Mode:
Full ISO Framing
and Error Checking
(Typical Mode)
Figure 6-27. User-Configurable Modes
The steps to enter Direct Mode are listed below, using SPI with SS communication method only as one
example, as Direct Modes are also possible with parallel and SPI without SS. The must enter Direct Mode
0 to accommodate non-ISO standard compliant card type communications. Direct Mode can be entered at
any time, so in the event a card type started with ISO standard communications, then deviated from the
standard after being identified and selected, the ability to go into Direct Mode 0 becomes very useful.
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Step 1: Configure Pins I/O_0 to I/O_2 for SPI with SS
Step 2: Set Pin 12 of the TRF7970A (ASK/OOK pin) to 0 for ASK or 1 for OOK
Step 3: Program the TRF7970A registers
The following registers need to be explicitly set before going into the Direct Mode.
1. ISO Control register (0x01) to the appropriate standard
– 0x02 for ISO 15693 High Data Rate
– 0x08 for ISO14443A (106 kbps)
– 0x1A for FeliCa 212 kbps
– 0x1B for FeliCa 424 kbps
2. Modulator and SYS_CLK register (0x09) to the appropriate clock speed and modulation
– 0x21 for 6.78 MHz Clock and OOK (100%) modulation
– 0x20 for 6.78 MHz Clock and ASK 10% modulation
– 0x22 for 6.78 MHz Clock and ASK 7% modulation
– 0x23 for 6.78 MHz Clock and ASK 8.5% modulation
– 0x24 for 6.78 MHz Clock and ASK 13% modulation
– 0x25 for 6.78 MHz Clock and ASK 16% modulation
(See register 0x09 definition for all other possible values)
Example register setting for ISO14443A at 106 kbps:
• ISO Control register (0x01) to 0x08
• RX No Response Wait Time register (0x07) to 0x0E
• RX Wait Time register (0x08) to 0x07
• Modulator control register (0x09) to 0x21 (or any custom modulation)
• RX Special Settings register (0x0A) to 0x20
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Step 4: Entering Direct Mode 0
The following registers need to be programmed to enter Direct Mode 0
1. Set bit B6 of the Modulator and SYS_CLK Control register (0x09) to 1.
2. Set bit B6 of the ISO Control (Register 01) to 0 for Direct Mode 0 (default its 0)
3. Set bit B6 of the Chip Status Control register (0x00) to 1 to enter Direct Mode
4. Send extra eight clock cycles (see Figure 6-28, this step is TRF7970A specific)
NOTE
–
–
It is important that the last write is not terminated with a stop condition. For SPI, this
means that Slave Select (I/O_4) stays low.
Sending a Stop condition terminates the Direct Mode and clears bit B6 in the Chip Status
Control register (0x00).
NOTE
Access to Registers, FIFO, and IRQ is not available during Direct Mode 0.
The reader enters the Direct Mode 0 when bit 6 of the Chip Status Control register (0x00) is set to a 1 and
stays in Direct Mode 0 until a stop condition is sent from the microcontroller.
NOTE
The write command should not be terminated with a stop condition (for example, in SPI
mode this is done by bringing the Slave Select line high after the register write), because the
stop condition terminates the direct mode and clears bit 6 of the Chip Status Control register
(0x00), making it a 0.
Figure 6-28. Entering Direct Mode 0
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Step 5: Transmit Data Using Direct Mode
The application now has direct control over the RF modulation through the MOD input (see Figure 6-29).
TRF7970A
Microcontroller
MOD
(Pin 14)
Drive the MOD pin
according to the data coding
specified by the standard
I/O_6
(Pin 23)
Decode the subcarrier
information according
to the standard
Figure 6-29. Direct Control Signals
The microcontroller is responsible for generating data according to the coding specified by the particular
standard. The microcontroller must generate SOF, EOF, Data, and CRC. In direct mode, the FIFO is not
used and no IRQs are generated. See the applicable ISO standard to understand bit and frame
definitions. As an example of what the developer sees when using DM0 in an actual application, Figure 630 is presented to clearly show the relationship between the MOD pin being controlled by the MCU and
the resulting modulated 13.56-MHz carrier signal.
Figure 6-30. TX Sequence Out in DM0
Step 6: Receive Data Using Direct Mode
After the TX operation is complete, the tag responds to the request and the subcarrier data is available on
pin I/O_6. The microcontroller needs to decode the subcarrier signal according to the standard. This
includes decoding the SOF, data bits, CRC, and EOF. The CRC then needs to be checked to verify data
integrity. The receive data bytes must be buffered locally.
As an example of the receive data bits and framing level according to the ISO14443A standard is shown
in Figure 6-31 (taken from ISO14443 specification and TRF7970A air interface).
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?
?
?
128/fc = 9.435 µs = tb (106-kbps data rate)
64/fc = 4.719 µs = tx time
32/fc = 2.359 µs = t1 time
tb = 9.44 µs
tx = 4.72 µs
Sequence Y = Carrier for 9.44 µs
t1 = 2.48 µs
Sequence Z = Pause for 2 to 3 µs,
Carrier for Remainder of 9.44 µs
Figure 6-31. Receive Data Bits and Framing Level
Figure 6-32 is presented to clearly show an example of what the developer should expect on the I/O_6
line during the RX process while in Direct Mode 0.
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Figure 6-32. RX Sequence on I/O_6 in DM0 (Analog Capture)
Step 7: Terminating Direct Mode 0
After the EOF is received, data transmission is over, and Direct Mode 0 can be terminated by sending a
Stop Condition (in the case of SPI, make the Slave Select go high). The TRF7970A is returned to default
state.
6.11 Special Direct Mode for Improved MIFARE™ Compatibility
See the application report TRF7970A Firmware Design Hints (SLOA159).
6.12 NFC Modes
6.12.1 Target
When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip
keeps the supply system on. If EN2 = L and EN = L the chip is in complete power down. To operate as
NFC target or Tag emulator, the MCU must load a value different from zero (0) in Target Detection Level
register (b0-b2) which enables the RF measurement system (supplied by VEXT, so it can operate also
during complete power down and consumes only 3.5 µA). The RF measurement constantly monitors the
RF signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the
in Target Detection Level register, the chip is automatically activated (EN is internal forced high). The
typical RF value that causes power-up for each value of B0 to B2 and the function of Target Detection
Level register is listed in Table 6-15.
NFC Target Detection Level Register (0x18) – defines level for RF level for wake-up and gives
information of NFCID size. This register is directly supplied by VEXT to ensure data retention during
complete power down.
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Table 6-15. NFC Target Detection Level Register
Bit
Signal Name
B7
Id_s1
B6
Id_s0
B5
Sdd_en
Comments
NFCID1 size used in 106 kbps passive target SDD
Automatic SDD using internal state machine and ID
stored in NFCID Number register (1)
1 = Enables internal SDD protocol
B4
(1)
Function
N/A
B3
Hi_rf
B2
Rfdet_h2
B1
Rfdet_h1
B0
Rfdet_h0
Extended range for RF measurements
RF field level required for system wake-up. If all
bits are 0, the RF level detection is switched off.
Comparator output is displayed in NFC Target
Protocol register B7 (rf_h)
Refer to the device errata (SLOZ011) for details on automatic SDD dependencies.
Default: reset to 00 at POR on VEXT (not on POR based on VDD_X), not reset at EN = 0
Table 6-16. Bits B0 to B3 of the NFC Target Detection Level Register
b0 B1 B2
000
001
010
011
100
101
110
111
B3 = 0
RF Vpp
B3 = 1
RF Vpp
Not active
480 mV
350 mV
250 mV
220 mV
190 mV
180 mV
170 mV
Not active
1500 mV
700 mV
500 mV
450 mV
400 mV
320 mV
280 mV
When the voltage supply system and the oscillator are started and is stable, the osc_ok goes high (B6 of
RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).
Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly
also during normal operation). This informs the MCU that the chip should start operation as an NFC
TARGET device.
When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set in IRQ
register. The MCU must set EN = H (confirm the power-up) in the time between the two IRQs as the
internal power-up ends after the second IRQ. The type and coding of the first initiator (or reader in the
case of a tag emulator) command define the communication protocol type which the target must use. So
the communication protocol type is available in the NFC Target Protocol register immediately after
receiving the first command. The coding of the NFC Target Protocol register is described next.
NFC Target Protocol Register (0x19) – displays the bit rate and protocol type (active or passive)
transmitted by initiator in the first command. It also displays the comparator outputs of both RF level
detectors.
Table 6-17. NFC Target Protocol Register
Bit
Signal Name
B7
Rf_h
1 = RF level is above the set wake-up level
The wake-up level is defined by bits b0-b3 of NFC
Target Detection Level register
B6
Rf_l
1 = RF level is above the RF collision avoidance
level.
The collision avoidance level is defined by bits b0b2 of NFC Low Field Detection Level register
B5
Function
Comments
N/A
B4
FeliCa
1 = FeliCa type
0 = ISO14443A type
The first initiator command had physical level
coding like FeliCa or like ISO14443A
B3
Pas106
Passive target 106 kbps or tag emulation
The first initiator/reader command was SENS_REQ
or ALL_REQ
B2
Pas14443B
Tag emulation ISO14443B
The first reader command was of ISO14443B type
B1
Nfcbr1
B0
Nfcbr0
Bit rate of first received command
00
01
10
11
= N/A
= 106 kbps
= 212 kbps
= 424 kbps
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Default: reset to 00 at POR and EN = L. B0 to B4 are automatically reset after MCU read operation. B6
and B7 continuously display the RF level comparator outputs.
Based on the first command from INITIATOR following actions are taken:
• If the first command is SENS_REQ or ALL_REQ, the TARGET must enter the SDD protocol for 106
kbps passive communication. If bit B5 in NFC Target Detection Level register is not set, the MCU
handles the SDD and the command received is send to FIFO. If the RF field is turned off (B7 in the
NFC Target Protocol register goes low) at any time, the system sends an IRQ to the MCU with bit B2
(RF field change) in the IRQ register set high. This informs the MCU that the procedure was aborted
and the system must be reset. The clock extractor is automatically activated in this mode.
• If the command is SENS_REQ or ALL_REQ and the Tag emulation bit in ISO Control register is set,
the system emulates an ISO14443A tag. The procedure does not differ from the one previously
described for a passive target at 106 kbps. The clock extractor is automatically activated in this mode.
• If the first command is a POLLING request, the system becomes a TARGET in passive communication
using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU directly. The
POLLING response is sent in one of the slots automatically calculated by the MCU (first slot starts
2.416 ms after the end of the command and slots follow in 1.208 ms).
• If the first command is ATR_REQ, the system operates as an active TARGET using the same
communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled
by MCU. The chip is only required to time the response collision avoidance, which is done on direct
command from MCU. When the RF field is switched on and the minimum wait time is elapsed, the chip
sends an IRQ with B1 (RF collision avoidance finished) set high. This signals the MCU that it can send
the reply.
• If the first command is coded as ISO14443B and the Tag emulation bit is set in the ISO Control
register, the system enters ISO14443B emulator mode. The anticollision must be handled by the MCU,
and the chip provides all physical level coding, decoding, and framing for this protocol.
Table 6-18 shows the function of the IRQ and Status register in NFC and Tag emulation. This register is
preset to 0 at POR = H or EN = L and at each write to ISO Control. It is also automatically reset at the end
of read phase. The reset also removes the IRQ flag.
Table 6-18. IRQ and Status Register (0x0C) for NFC and Card Emulation Operation
Bit
(1)
50
Name
Function
(1)
Description
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of
TX but the interrupt request (IRQ = 1) is sent when TX is
finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress.
The flag is set at the start of RX but the interrupt request
(IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ
Levels (0x14) register
B4
Irq_err1
CRC error
Indicates receive CRC error only if B7 (no RX CRC) of ISO
Control register is set to 0.
B3
Irq_err2
Parity error
Indicates parity error for ISO14443A
B2
Irq_err3
Byte framing or EOF error
Indicates framing error
Collision error
Collision error for ISO14443A and ISO15693 single
subcarrier. Bit is set if more then 6 or 7 (as defined in
register 0x01) are detected inside one bit period of
ISO14443A 106 kbps. Collision error bit can also be
triggered by external noise.
No-response time interrupt
No response within the "No-response time" defined in RX
No-response Wait Time register (0x07). Signals the MCU
that next slot command can be sent. Only for ISO15693.
B1
Irq_col
B0
Irq_noresp
Displays the cause of IRQ and TX/RX status
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6.12.2 Initiator
The chip is fully controlled by the MCU as in RFID reader operation. The MCU activates the chip and
writes the mode selection in the ISO Control register. The MCU uses RF collision avoidance commands,
so it is relieved of any real-time task. The normal transmit and receive procedure (through the FIFO) are
used to communicate with the TARGET device as described in Section 6.10.
6.13 Direct Commands from MCU to Reader
6.13.1 Command Codes
Table 6-19. Address and Command Word Bit Distribution
Command Code
Command
0x00
Idle
0x03
Software Initialization
0x04
Perform RF Collision Avoidance
0x05
Perform response RF Collision Avoidance
Comments
Same as Power on Reset
0x06
Perform response RF Collision Avoidance (n = 0)
0x0F
Reset
0x10
Transmission without CRC
0x11
Transmission with CRC
0x12
Delayed Transmission without CRC
0x13
Delayed Transmission with CRC
0x14
End of Frame/Transmit Next Time Slot
0x15
Close Slot Sequence
0x16
Block Receiver
0x17
Enable Receiver
0x18
Test internal RF (RSSI at RX input with TX off)
0x19
Test external RF (RSSI at RX input with TX on)
0x1A
Receiver Gain Adjust
ISO15693
The command code values from Table 6-19 are substituted in Table 6-20, Bits 0 through 4. Also, the
most-significant bit (MSB) in Table 6-20 must be set to 1. ( Table 6-20 is same as Table 6-11, shown here
again for user clarity).
Table 6-20. Address and Command Word Bit Distribution
Bit
Description
Bit Function
Address
Command
B7
Command control bit
0 = address
1 = command
0
1
B6
Read/Write
0 = write
1 = read
R/W
0
B5
Continuous address mode
1 = Continuous mode
R/W
0
B4
Address/Command bit 4
Adr 4
Cmd 4
B3
Address/Command bit 3
Adr 3
Cmd 3
B2
Address/Command bit 2
Adr 2
Cmd 2
B1
Address/Command bit 1
Adr 1
Cmd 1
B0
Address/Command bit 0
Adr 0
Cmd 0
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The MSB determines if the word is to be used as a command or address. The last two columns of
Table 6-20 show the function of each bit, depending on whether address or command is written.
Command mode is used to enter a command resulting in reader action (initialize transmission, enable
reader, and turn reader on or off).
6.13.1.1 Idle (0x00)
This command issues dummy clock cycles. In parallel mode, one cycle is issued. In SPI mode, eight
cycles are issued.
6.13.1.2 Software Initialization (0x03)
This command starts a Power on Reset. After sending this command, the register values change as
shown in Table 6-21.
Table 6-21. Register Values After Sending Software
Initialization (0x03)
Address
(1)
52
Register
Value
0x00
Chip Status Control
0x01
ISO Control
0x02
ISO14443B TX options
0x00
0x03
ISO14443A high bit rate options
0x00
0x04
TX timer setting, H-byte
0xC1 (1)
0x05
TX timer setting, L-byte
0xC1 (1)
0x06
TX pulse-length control
0x00
0x07
RX no response wait
0x0E
0x08
RX wait time
0x09
Modulator and SYS_CLK control
0x0A
RX Special Setting
0x01
0x21 (1)
0x07 (1)
0x91
0x10 (1)
0x0B
Regulator and I/O control
0x0C
IRQ status
0x87
0x00
0x0D
Collision position and interrupt mask
0x3E
0x0E
Collision position
0x00
0x0F
RSSI levels and oscillator status
0x40
0x10
Special Function
0x00
0x11
Special Function
0x00
0x12
RAM
0x00
0x13
RAM
0x00
0x14
Adjustable FIFO IRQ Levels
0x00
0x15
Reserved
0x00
0x16
NFC Low Field Detection Level
0x00
0x18
NFC Target Detection Level
0x00
0x19
NFC Target Protocol
0x00
0x1A
Test
0x00
0x1B
Test
0x00
0x1C
FIFO status
0x00
Differs from default at POR
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6.13.1.3 Initial RF Collision Avoidance (0x04)
This command executes the initial collision avoidance and sends out IRQ after 5 ms from establishing RF
field (so the MCU can start sending commands/data). If the external RF field is present (higher than the
level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on and
hence a different IRQ is returned.
6.13.1.4 Response RF Collision Avoidance (0x05)
This command executes the response collision avoidance and sends out IRQ after 75 µs from establishing
RF field (so the MCU can start sending commands/data). If the external RF field is present (higher than
the level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on
and hence a different IRQ is returned.
6.13.1.5 Response RF Collision Avoidance (0x06, n = 0)
This command executes the response collision avoidance without random delay. It sends out IRQ after 75
µs from establishing RF field (so the MCU can start sending commands/data). If the external RF field is
present (higher than the level set in NFC Low Field Detection Level register (0x16)) then the RF field can
not be switched on and hence a different IRQ is returned.
6.13.1.6 Reset (0x0F)
The reset command clears the FIFO contents and FIFO status register (0x1C). It also clears the register
storing the collision error location (0x0E).
6.13.1.7 Transmission With CRC (0x11)
The transmission command must be sent first, followed by transmission length bytes, and FIFO data. The
reader starts transmitting after the first byte is loaded into the FIFO. The CRC byte is included in the
transmitted sequence.
6.13.1.8 Transmission Without CRC (0x10)
Same as Section 6.13.1.7 with CRC excluded.
6.13.1.9 Delayed Transmission With CRC (0x13)
The transmission command must be sent first, followed by the transmission length bytes, and FIFO data.
The reader transmission is triggered by the TX timer.
6.13.1.10 Delayed Transmission Without CRC (0x12)
Same as Section 6.13.1.9 with CRC excluded.
6.13.1.11 Transmit Next Time Slot (0x14)
When this command is received, the reader transmits the next slot command. The next slot sign is defined
by the protocol selection.
6.13.1.12 Block Receiver (0x16)
The block receiver command puts the digital part of receiver (bit decoder and framer) in reset mode. This
is useful in an extremely noisy environment, where the noise level could otherwise cause a constant
switching of the subcarrier input of the digital part of the receiver. The receiver (if not in reset) would try to
catch a SOF signal, and if the noise pattern matched the SOF pattern, an interrupt would be generated,
falsely signaling the start of an RX operation. A constant flow of interrupt requests can be a problem for
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the external system (MCU), so the external system can stop this by putting the receive decoders in reset
mode. The reset mode can be terminated in two ways. The external system can send the enable receiver
command. The reset mode is also automatically terminated at the end of a TX operation. The receiver can
stay in reset after end of TX if the RX wait time register (0x08) is set. In this case, the receiver is enabled
at the end of the wait time following the transmit operation.
6.13.1.13 Enable Receiver (0x17)
This command clears the reset mode in the digital part of the receiver if the reset mode was entered by
the block receiver command.
6.13.1.14 Test Internal RF (RSSI at RX Input With TX ON) (0x18)
The level of the RF carrier at RF_IN1 and RF_IN2 inputs is measured. Operating range between 300 mVP
and 2.1 VP (step size is 300 mV). The two values are displayed in the RSSI levels register (0x0F). The
command is intended for diagnostic purposes to set correct RF_IN levels. Optimum RFIN input level is
approximately 1.6 VP or code 5 to 6. The nominal relationship between the RF peak level and RSSI code
is shown in Table 6-22 and in Section 6.5.1.1.
NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by Enable RX command. The Check RF
commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-22. Test Internal RF Peak Level to RSSI Codes
RF_IN1 [mVPP]
300
600
900
1200
1500
1800
Decimal Code
1
2
3
4
5
6
7
001
010
011
001
101
011
111
Binary Code
2100
6.13.1.15 Test External RF (RSSI at RX Input with TX OFF) (0x19)
This command can be used in active mode when the RF receiver is switched on but RF output is switched
off. This means bit B1 = 1 in Chip Status Control Register. The level of RF signal received on the antenna
is measured and displayed in the RSSI Levels register (0x0F). The relation between the 3 bit code and the
external RF field strength [A/m] must be determinate by calculation or by experiments for each antenna
type as the antenna Q and connection to the RF input influence the result. The nominal relation between
the RF peak to peak voltage in the RF_IN1 input and RSSI code is shown in Table 6-23 and in
Section 6.5.1.2.
NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by an Enable RX command. The Check
RF commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-23. Test External RF Peak Level to RSSI Codes
RF_IN1 [mVPP]
40
60
80
100
140
180
Decimal Code
1
2
3
4
5
6
7
001
010
011
001
101
011
111
Binary Code
54
Detailed Description
300
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6.13.1.16 Receiver Gain Adjust (0x1A)
This command should be executed when the MCU determines that no TAG response is coming and when
the RF and receivers are switched ON. When this command is received, the reader observes the digitized
receiver output. If more than two edges are observed in 100 ms, the window comparator voltage is
increased. The procedure is repeated until the number of edges (changes of logical state) of the digitized
reception signal is less than 2 (in 100 ms). The command can reduce the input sensitivity in 5-dB
increments up to 15 dB. This command ensures better operation in a noisy environment. The gain setting
is reset to maximum gain at EN = 0 and POR = 1.
6.14 Register Description
6.14.1 Register Preset
After power-up and the EN pin low-to-high transition, the reader is in the default mode. The default
configuration is ISO15693, single subcarrier, high data rate, 1-out-of-4 operation. The low-level option
registers (0x02 to 0x0B) are automatically set to adapt the circuitry optimally to the appropriate protocol
parameters. When entering another protocol (by writing to the ISO Control register 0x01), the low-level
option registers (0x02 to 0x0B) are automatically configured to the new protocol parameters. After
selecting the protocol, it is possible to change some low-level register contents if needed. However,
changing to another protocol and then back, reloads the default settings, and so then the custom settings
must be reloaded.
The Clo0 and Clo1 register (0x09) bits, which define the microcontroller frequency available on the
SYS_CLK pin, are the only two bits in the configuration registers that are not cleared during protocol
selection.
6.14.2 Register Overview
Table 6-24. Register Definitions
Address
Register
Read/Write
0x00
Chip Status Control
R/W
0x01
ISO Control
R/W
0x02
ISO14443B TX options
R/W
0x03
ISO14443A high bit rate options
R/W
0x04
TX timer setting, H-byte
R/W
0x05
TX timer setting, L-byte
R/W
0x06
TX pulse-length control
R/W
0x07
RX no response wait
R/W
0x08
RX wait time
R/W
0x09
Modulator and SYS_CLK control
R/W
0x0A
RX Special Setting
R/W
0x0B
Regulator and I/O control
R/W
0x10
Special Function Register, Preset 0x00
R/W
0x11
Special Function Register, Preset 0x00
R/W
0x14
Adjustable FIFO IRQ Levels Register
R/W
0x15
Reserved
R/W
0x16
NFC Low Field Detection Level
R/W
0x17
NFCID1 Number (up to 10 bytes wide)
W
0x18
NFC Target Detection Level
R/W
Main Control Registers
Protocol Sub-Setting Registers
Detailed Description
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Table 6-24. Register Definitions (continued)
Address
Register
Read/Write
0x19
NFC Target Protocol
R/W
Status Registers
0x0C
IRQ status
R
0x0D
Collision position and interrupt mask register
R/W
0x0E
Collision position
R
0x0F
RSSI levels and oscillator status
R
0x12
RAM
R/W
0x13
RAM
R/W
0x1A
Test Register. Preset 0x00
R/W
0x1B
Test Register. Preset 0x00
R/W
0x1C
FIFO status
R
0x1D
TX length byte 1
R/W
0x1E
TX length byte 2
R/W
0x1F
FIFO I/O register
R/W
RAM
Test Registers
FIFO Registers
56
Detailed Description
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6.14.3 Detailed Register Description
6.14.3.1 Main Configuration Registers
6.14.3.1.1 Chip Status Control Register (0x00)
Table 6-25. Chip Status Control Register (0x00)
Function: Control of Power mode, RF on/off, AGC, AM/PM, Direct Mode
Default: 0x01, preset at EN = L or POR = H
Bit
B7
B6
B5
B4
B3
B2
B1
B0
Name
stby
direct
rf_on
Function
Description
1 = Standby Mode
Standby mode keeps all supply regulators, 13.56-MHz SYS_CLK oscillator
running. (typical start-up time to full operation 100 µs)
0 = Active Mode
Active Mode (default)
1 = Direct Mode 0 or 1
Provides user direct access to AFE (Direct Mode 0) or allows user to add their
own framing (Direct Mode 1). Bit 6 of ISO Control register must be set by user
before entering Direct Mode 0 or 1.
0 = Direct Mode 2 (default)
Uses SPI or parallel communication with automatic framing and ISO decoders
1 = RF output active
Transmitter on, receivers on
0 = RF output not active
Transmitter off
1 = half output power
TX_OUT (pin 5) = 8-Ω output impedance P = 100 mW (20 dBm) at 5 V,
P = 33 mW (+15 dBm) at 3.3 V
0 = full output power
TX_OUT (pin 5) = 4-Ω output impedance P = 200 mW (+23 dBm) at 5 V,
P = 70 mW (+18 dBm) at 3.3 V
1 = selects Aux RX input
RX_IN2 input is used
0 = selects Main RX input
RX_IN1 input is used
1 = AGC on
Enables AGC (AGC gain can be set in register 0x0A)
0 = AGC off
AGC block is disabled
1 = Receiver activated for
external field measurement
Forced enabling of receiver and TX oscillator. Used for external field
measurement.
0 = Automatic Enable
Allows enable of the receiver by Bit 5 of this register (0x00)
1 = 5 V operation
0 = 3 V operation
Selects the VIN voltage range
rf_pwr
pm_on
agc_on
rec_on
vrs5_3
6.14.3.1.2 ISO Control Register (0x01)
Table 6-26. ISO Control Register (0x01)
Function: Controls the selection of ISO Standard protocol, Direct Mode and Receive CRC
Default: 0x02 (ISO15693 high bit rate, one subcarrier, 1 out of 4); it is preset at EN = L or POR = H
Bit
Name
Function
Description
B7
rx_crc_n
CRC Receive selection
0 = RX CRC (CRC is present in the response)
1 = no RX CRC (CRC is not present in the response) (1)
B6
dir_mode
Direct mode type selection
0 = Direct Mode 0
1 = Direct Mode 1
B5
rfid
RFID / Reserved
0 = RFID Mode
1 = NFC or Card Emulation Mode
RFID: See Table 6-27 for B0:B4 settings based on ISO protocol desired by
application
(1)
B4
iso_4
RFID / NFC Target
B3
iso_3
RFID / NFC Mode
NFC:
0 = target
1 = initiator
NFC:
0 = passive mode
1 = active mode
Only applicable to ISO-14443A and ISO-15693
Detailed Description
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Table 6-26. ISO Control Register (0x01) (continued)
B2
iso_2
RFID / Card Emulation
NFC:
0 = NFC Normal Modes
1 = Card Emulation Mode
B1
iso_1
RFID / NFC bit rate
NFC:
0 = bit rate selection or card emulation selection, see Table 6-28
B0
iso_0
RFID / NFC bit rate
NFC:
0 = bit rate selection or card emulation selection, see Table 6-28
Table 6-27. ISO Control Register ISO_x Settings, RFID Mode
ISO_4
ISO_3
ISO_2
ISO_1
ISO_0
0
0
0
0
0
ISO15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 4
0
0
0
0
1
ISO15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 256
0
0
0
1
0
ISO15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 4
0
0
0
1
1
ISO15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 256
0
0
1
0
0
ISO15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of 4
0
0
1
0
1
ISO15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of 256
0
0
1
1
0
ISO15693 high bit rate, 26.69 kbps, double subcarrier, 1 out of 4
0
0
1
1
1
ISO15693 high bit rate, 26.69 kbps, double subcarrier,
1 out of 256
0
1
0
0
0
ISO14443A RX bit rate, 106 kbps
0
1
0
0
1
ISO14443A RX high bit rate, 212 kbps
0
1
0
1
0
ISO14443A RX high bit rate, 424 kbps
0
1
0
1
1
ISO14443A RX high bit rate, 848 kbps
0
1
1
0
0
ISO14443B RX bit rate, 106 kbps
0
1
1
0
1
ISO14443B RX high bit rate, 212 kbps
0
1
1
1
0
ISO14443B RX high bit rate, 424 kbps
0
1
1
1
1
ISO14443B RX high bit rate, 848 kbps
1
0
0
1
1
Reserved
1
0
1
0
0
Reserved
1
1
0
1
0
FeliCa 212 kbps
1
1
0
1
1
FeliCa 424 kbps
(1)
Protocol
Remarks
Default for reader
RX bit rate
(1)
RX bit rate
(1)
For ISO14443A/B, when bit rate of TX is different from RX, settings can be done in register 0x02 or 0x03.
Table 6-28. ISO Control Register ISO_x Settings,
NFC Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1, B2 = 1)
58
NFC
(B5 = 1, B2 = 0)
Card Emulation
(B5 = 1, B2 = 1)
0
N/A
ISO14443A
1
106 kbps
ISO14443B
1
0
212 kbps
N/A
1
1
424 kbps
N/A
ISO_1
ISO_0
0
0
Detailed Description
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6.14.3.2 Control Registers – Sub Level Configuration Registers
6.14.3.2.1 ISO14443 TX Options Register (0x02)
Table 6-29. ISO14443 TX Options Register (0x02)
Function: Selects the ISO subsets for ISO14443 – TX
Default: 0x00 at POR = H or EN = L
Bit
Name
B7
egt2
TX EGT time select MSB
B6
egt1
TX EGT time select
B5
egt0
TX EGT time select LSB
B4
eof_l0
1 = EOF→ 0 length 11 etu
0 = EOF→ 0 length 10 etu
B3
sof_l1
1 = SOF→ 1 length 03 etu
0 = SOF→ 1 length 02 etu
B2
sof _l0
1 = SOF→ 0 length 11 etu
0 = SOF→ 0 length 10 etu
B1
l_egt
1 = EGT after each byte
0 = EGT after last byte is
omitted
Auto SDD_SAK
1 = ISO14443A Layer 4
compliant (in SAK
response)
0 = Not Layer 4 compliant
(in SAK response)
B0
Function
Description
Three bit code defines the number of etu (0-7) which separate two characters.
ISO14443B TX only.
ISO14443B TX only
For use with Auto SDD configuration, makes B6 in ISO14443A response 1 or 0,
indicating Layer 4 compliance (or not), for all other cases, this bit is unused
6.14.3.2.2 ISO14443 High-Bit-Rate and Parity Options Register (0x03)
Table 6-30. ISO14443 High-Bit-Rate and Parity Options Register (0x03)
Function: Selects the ISO subsets for ISO14443 – TX
Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register
Bit
Name
B7
dif_tx_br
B6
tx_br1
Function
Description
TX bit rate different from RX
Valid for ISO14443A/B high bit rate
bit rate enable
tx_br1 = 0, tx_br
tx_br1 = 0, tx_br
tx_br1 = 1, tx_br
tx_br1 = 1, tx_br
TX bit rate
B5
tx_br0
B4
parity-2tx
1 = parity odd except last
byte which is even for TX
B3
parity-2rx
1 = parity odd except last
byte which is even for RX
=0→
=1→
=0→
=1→
106 kbps
212 kbps
424 kbps
848 kbps
For 14443A high bit rate, coding and decoding
B2
Unused
B1
Unused
B0
Unused
Detailed Description
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6.14.3.2.3 TX Timer High Byte Control Register (0x04)
Table 6-31. TX Timer High Byte Control Register (0x04)
Function: For Timings
Default: 0xC2 at POR = H or EN = L, and at each write to ISO Control register
Bit
Name
B7
tm_st1
Timer Start Condition
Function
B6
tm_st0
Timer Start Condition
B5
tm_lengthD
Timer Length MSB
B4
tm_lengthC
Timer Length
B3
tm_lengthB
Timer Length
B2
tm_lengthA
Timer Length
B1
tm_length9
Timer Length
B0
tm_length8
Timer Length LSB
Description
tm_st1 = 0, tm_st0 = 0 →
tm_st1 = 0, tm_st0 = 1 →
tm_st1 = 1, tm_st0 = 0 →
tm_st1 = 1, tm_st0 = 1 →
beginning of TX SOF
end of TX SOF
beginning of RX SOF
end of RX SOF
6.14.3.2.4 TX Timer Low Byte Control Register (0x05)
Table 6-32. TX Timer Low Byte Control Register (0x05)
Function: For Timings
Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register
60
Bit
Name
Function
Description
B7
tm_length7
Timer Length MSB
B6
tm_length6
Timer Length
B5
tm_length5
Timer Length
B4
tm_length4
Timer Length
B3
tm_length3
Timer Length
Step size is 590 ns
B2
tm_length2
Timer Length
All bits low = timer disabled (0x00)
B1
tm_length1
Timer Length
Preset 0x00 for all other protocols
B0
tm_length0
Timer Length LSB
Defines the time when delayed transmission is started.
RX wait range is 590 ns to 9.76 ms (1 to 16383)
Detailed Description
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6.14.3.2.5 TX Pulse Length Control Register (0x06)
The length of the modulation pulse is defined by the protocol selected in the ISO Control register 0x01.
With a high Q antenna, the modulation pulse is typically prolonged, and the tag detects a longer pulse
than intended. For such cases, the modulation pulse length can be corrected by using the TX Pulse
Length Control register (0x06). If the register contains all zeros, then the pulse length is governed by the
protocol selection. If the register contains a value other than 0x00, the pulse length is equal to the value of
the register in 73.7-ns increments. This means the range of adjustment can be 73.7 ns to 18.8 µs.
Table 6-33. TX Pulse Length Control Register (0x06)
Function: Controls the length of TX pulse
Default: 0x00 at POR = H or EN = L and at each write to ISO Control register.
Bit
Name
B7
Pul_p2
Function
B6
Pul_p1
B5
Pul_p0
B4
Pul_c4
The following default timings are preset by the ISO Control register (0x01):
B3
Pul_c3
9.44 µs → ISO15693 (TI Tag-It HF-I)
B2
Pul_c2
11 µs → Reserved
B1
Pul_c1
2.36 µs → ISO14443A at 106 kbps
Pulse length MSB
Description
The pulse range is 73.7 ns to 18.8 µs (1….255), step size 73.7 ns.
All bits low (00): pulse length control is disabled.
1.4 µs → ISO14443A at 212 kbps
B0
Pul_c0
Pulse length LSB
737 ns → ISO14443A at 424 kbps
442 ns → ISO14443A at 848 kbps; pulse length control disabled
6.14.3.2.6 RX No Response Wait Time Register (0x07)
The RX No Response timer is controlled by the RX NO Response Wait Time Register 0x07. This timer
measures the time from the start of slot in the anticollision sequence until the start of tag response. If there
is no tag response in the defined time, an interrupt request is sent and a flag is set in IRQ status control
register 0x0C. This enables the external controller to be relieved of the task of detecting empty slots. The
wait time is stored in the register in increments of 37.76 µs. This register is also preset, automatically, for
every new protocol selection. Sending a Reset FIFO (0x0F) direct command after a TX Complete interrupt
will disable this feature.
Table 6-34. RX No Response Wait Time Register (0x07)
Function: Defines the time when "no response" interrupt is sent; only for ISO15693
Default: 0x0E at POR = H or EN = L and at each write to ISO Control register
Bit
Name
Function
B7
NoResp7
B6
NoResp6
B5
NoResp5
Defines the time when "no response" interrupt is sent. It starts from the end of
TX EOF. RX no response wait range is 37.76 µs to 9628 µs (1 to 255), step
size is: 37.76 µs.
B4
NoResp4
The following default timings are preset by the ISO Control register (0x01):
B3
NoResp3
390 µs → Reserved
B2
NoResp2
529 µs → for all protocols supported, but not listed here
B1
NoResp1
B0
NoResp0
No response MSB
Description
604 µs → Reserved
No response LSB
755 µs → ISO15693 high data rate (TI Tag-It HF-I)
1812 µs → ISO15693 low data rate (TI Tag-It HF-I)
Detailed Description
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6.14.3.2.7 RX Wait Time Register (0x08)
The RX-wait-time timer is controlled by the value in the RX wait time register 0x08. This timer defines the
time after the end of the transmit operation in which the receive decoders are not active (held in reset
state). This prevents incorrect detections resulting from transients following the transmit operation. The
value of the RX wait time register defines this time in increments of 9.44 µs. This register is preset at
every write to ISO Control register 0x01 according to the minimum tag response time defined by each
standard.
Table 6-35. RX Wait Time Register (0x08)
Function: Defines the time after TX EOF when the RX input is disregarded for example, to block out electromagnetic disturbance
generated by the responding card.
Default: 0x1F at POR = H or EN = L and at each write toISO control register.
Bit
Name
Function
Description
B7
Rxw7
B6
Rxw6
Defines the time after the TX EOF during which the RX input is ignored. Time
starts from the end of TX EOF.
B5
Rxw5
RX wait range is 9.44 µs to 2407 µs (1 to 255), Step size 9.44 µs.
B4
Rxw4
B3
Rxw3
B2
Rxw2
B1
Rxw1
B1
Rxw0
The following default timings are preset by the ISO Control register (0x01):
RX wait time
9.44 µs → FeliCa
66 µs → ISO14443A and B
180 µs → Reserved
62
293 µs → ISO15693 (TI Tag-It HF-I)
Detailed Description
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6.14.3.2.8 Modulator and SYS_CLK Control Register (0x09)
The frequency of SYS_CLK (pin 27) is programmable by the bits B4 and B5 of this register. The frequency
of the TRF7970A system clock oscillator is divided by 1, 2 or 4 resulting in available SYS_CLK
frequencies of 13.56 MHz or 6.78 MHz or 3.39 MHz.
The ASK modulation depth is controlled by bits B0, B1 and B2. The range of ASK modulation is 7% to
30% or 100% (OOK). The selection between ASK and OOK (100%) modulation can also be done using
direct input OOK (pin 12). The direct control of OOK/ASK using OOK pin is only possible if the function is
enabled by setting B6 = 1 (en_ook_p) in this register (0x09) and the ISO Control Register (0x01, B6 = 1).
When configured this way, the MOD (pin 14) is used as input for the modulation signal.
Table 6-36. Modulator and SYS_CLK Control Register (0x09)
Function: Controls the modulation input and depth, ASK / OOK control and clock output to external system (MCU)
Default: 0x91 at POR = H or EN = L, and at each write to ISO control register, except Clo1 and Clo0.
Bit
Name
B7
27MHz
Enables 27.12-MHz crystal
en_ook_p
1 = Enables external
selection of ASK or OOK
modulation
0 = Default operation as
defined in B0 to B2 (0x09)
B6
Function
Description
Default = 1 (enabled)
Enable ASK/OOK pin (pin 12) for "on the fly change" between any preselected
ASK modulation as defined by B0 to B2 and OOK modulation:
If B6 is 1, pin 12 is configured as follows:
1 = OOK modulation
0 = Modulation as defined in B0 to B2 (0x09)
B5
Clo1
SYS_CLK output frequency
MSB
B4
Clo0
SYS_CLK output frequency
LSB
B3
en_ana
1 = Sets pin 12 (ASK/OOK)
as an analog output
0 = Default
B2
B1
B0
Pm2
Pm1
Pm0
Modulation depth MSB
Modulation depth
Modulation depth LSB
SYS_CLK Output SYS_CLK Output
(if 13.56-MHz
(if 27.12-MHz
crystal is used)
crystal is used)
Clo1
Clo0
0
0
Disabled
Disabled
0
1
3.39 MHz
6.78 MHz
1
0
6.78 MHz
13.56 MHz
1
1
13.56 MHz
27.12 MHz
For test and measurement purpose. ASK/OOK pin 12 can be used to monitor
the analog subcarrier signal before the digitizing with DC level equal to AGND.
Pm2
Pm1
Pm0
Mod Type and %
0
0
0
ASK 10%
0
0
1
OOK (100%)
0
1
0
ASK 7%
0
1
1
ASK 8.5%
1
0
0
ASK 13%
1
0
1
ASK 16%
1
1
0
ASK 22%
1
1
1
ASK 30%
Detailed Description
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6.14.3.2.9 RX Special Setting Register (Address 0x0A)
Table 6-37. RX Special Setting Register (Address 0x0A)
Function: Sets the gains and filters directly
Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register 0x01. When bits B7, B6, B5 and B4 are all zero, the
filters are set for ISO14443B (240 kHz to 1.4 MHz).
Bit
Name
B7
C212
Bandpass 110 kHz to 570 kHz
Function
Appropriate for 212-kHz subcarrier system (FeliCa)
B6
C424
Bandpass 200 kHz to 900 kHz
Appropriate for 424-kHz subcarrier used in ISO15693
B5
M848
Bandpass 450 kHz to 1.5 MHz
Appropriate for Manchester-coded 848-kHz subcarrier used in ISO14443A
and B
B4
hbt
Bandpass 100 kHz to 1.5 MHz
Gain reduced for 18 dB
Appropriate for highest bit rate (848 kbps) used in high-bit-rate ISO14443
B3
gd1
B2
gd2
00
01
10
11
Sets the RX gain reduction, and reduces sensitivity
B1
agcr
B0
no-lim
= Gain
= Gain
= Gain
= Gain
reduction
reduction
reduction
reduction
Description
0 dB
for 5 dB
for 10 dB
for 15 dB
AGC activation level change
AGC activation level changed from five times the digitizing level to three
times the digitizing level.
1 = 3x
0 = 5x
AGC action is not limited in time
AGC action can be done any time during receive process. It is not limited
to the start of receive ("max hold").
1 = continuously – no time limit
0 = 8 subcarrier pulses
The first four steps of the AGC control are comparator adjustment. The second three steps are real gain
reduction done automatically by AGC control. The AGC is turned on after TX.
The first gain and filtering stage following the RF envelope detector has a nominal gain of 15 and the 3-dB
band-pass frequencies are adjustable in the range from 100 kHz to 400 kHz for high pass and 600 kHz to
1.5 MHz for low pass. The next gain and filtering stage has a nominal gain of 8 and the frequency
characteristic identical to first stage. The filter setting is done automatically with internal preset for each
new selection of communication standard in ISO Control register (0x01). Additional corrections can be
done by directly writing into the RX Special Setting register 0x0A.
The second receiver gain stage and digitizer stage are included in the AGC loop. The AGC loop can be
activated by setting the bit B2 = 1 (agc-on) in Chip Status Control register 0x00. If activated the AGC
monitors the signal level at the input of digitizing stage. If the signal level is significantly higher than the
digitizing threshold level, the gain reduction is activated. The signal level, at which the action is started, is
by default five times the digitizing threshold level. It can be reduced to three times the digitizing level by
setting bit B1 = 1 (agcr) in RX Special Setting register (0x0A).
The AGC action is fast and it typically finishes within eight subcarrier pulses. By default the AGC action is
blocked after first few pulses of subcarrier signal so AGC cannot interfere with signal reception during rest
of data packet. In certain cases, this is not optimal, so this blocking can be removed by setting B0 = 1
(no_lim) in RX Special Setting register (0x0A).
NOTE
The setting of bits B4, B5, B6 and B7 to zero selects bandpass characteristic of 240 kHz to
1.4 MHz. This is appropriate for ISO14443B, FeliCa protocol, and ISO14443A higher bit
rates 212 kbps and 424 kbps.
64
Detailed Description
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6.14.3.2.10 Regulator and I/O Control Register (0x0B)
Table 6-38. Regulator and I/O Control Register (0x0B)
Function: Control the three voltage regulators
Default: 0x87 at POR = H or EN = L
Bit
Name
Function
Description
0 = Manual settings; see B0
to B2 in Table 6-39 and
Auto system sets VDD_RF = VIN – 250 mV and VDD_A = VIN – 250 mV and
Table 6-40
VDD_X= VIN – 250 mV, but not higher than 3.4 V.
1 = Automatic setting
B7
auto_reg
B6
en_ext_pa
Support for external power
amplifier
Internal peak detectors are disabled, receiver inputs (RX_IN1 and RX_IN2)
accept externally demodulated subcarrier. At the same time ASK/OOK pin 12
becomes modulation output for external TX amplifier.
B5
io_low
1 = enable low peripheral
communication voltage
When B5 = 1, maintains the output driving capabilities of the I/O pins connected
to the level shifter under low voltage operation. Should be set 1 when VDD_I/O
voltage is between 1.8 V to 2.7 V.
B4
Unused
No function
Default is 0.
B3
Unused
No function
Default is 0.
B2
vrs2
B1
vrs1
Voltage set MSB voltage
set LSB
Vrs3_5 = L: VDD_RF, VDD_A, VDD_X range 2.7 V to 3.4 V; see Table 6-39 and
Table 6-40
B0
vrs0
Table 6-39. Supply-Regulator Setting – Manual 5-V System
Register
Option Bits Setting in Control Register
B7
B6
B5
B4
B3
B2
B1
00
Action
B0
1
5-V system
0B
0
0B
0
1
1
1
Manual regulator setting
VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
1
0
VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
0
1
VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
0
0
VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
1
1
VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
1
0
VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
0
1
VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
0
0
VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V
Table 6-40. Supply-Regulator Setting – Manual 3-V System
Register
Option Bits Setting in Control Register
B7
B6
B5
B4
B3
B2
B1
00
Action
B0
0
3-V system
0B
0
0B
0
1
1
1
Manual regulator setting
VDD_RF = 3.4 V, VDD_A and VDD_X = 3.4 V
0B
0
1
1
0
VDD_RF = 3.3 V, VDD_A and VDD_X = 3.3 V
0B
0
1
0
1
VDD_RF = 3.2 V, VDD_A and VDD_X = 3.2 V
0B
0
1
0
0
VDD_RF = 3.1 V, VDD_A and VDD_X = 3.1 V
0B
0
0
1
1
VDD_RF = 3.0 V, VDD_A and VDD_X = 3.0 V
0B
0
0
1
0
VDD_RF = 2.9 V, VDD_A and VDD_X = 2.9 V
0B
0
0
0
1
VDD_RF = 2.8 V, VDD_A and VDD_X = 2.8 V
0B
0
0
0
0
VDD_RF = 2.7 V, VDD_A and VDD_X = 2.7 V
Detailed Description
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Table 6-41. Supply-Regulator Setting – Automatic 5-V System
Register
Option Bits Setting in Control Register
B7
B6
B5
B4
B3
B2
B1
x (1)
0
00
0B
(1)
1
Action
B0
1
5-V system
0
Automatic regulator setting 400-mV difference
x = don't care
Table 6-42. Supply-Regulator Setting – Automatic 3-V System
Register
Option Bits Setting in Control Register
B7
B6
B5
B4
B3
B2
B1
x (1)
0
00
0B
(1)
1
Action
B0
0
3-V system
0
Automatic regulator setting 400-mV difference
x = don't care
6.14.3.3 Status Registers
6.14.3.3.1 IRQ Status Register (0x0C)
Table 6-43. IRQ Status Register (0x0C)
Function: Information available about TRF7970A IRQ and TX/RX status
Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read
phase. The reset also removes the IRQ flag.
Bit
Name
Function
Description
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of TX but the interrupt
request (IRQ = 1) is sent when TX is finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress. The flag is set at the
start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)
register
B4
Irq_err1
CRC error
Indicates receive CRC error only if B7 (no RX CRC) of ISO Control register is
set to 0.
B3
Irq_err2
Parity error
Indicates parity error for ISO14443A
B2
Irq_err3
Byte framing or EOF error
Indicates framing error
B1
Irq_col
Collision error
Collision error for ISO14443A and ISO15693 single subcarrier. Bit is set if more
then 6 or 7 (as defined in register 0x01) are detected inside one bit period of
ISO14443A 106 kbps. Collision error bit can also be triggered by external
noise.
B0
Irq_noresp
No-response time interrupt
No response within the "No-response time" defined in RX No-response Wait
Time register (0x07). Signals the MCU that next slot command can be sent.
Only for ISO15693.
To reset (clear) the register 0x0C and the IRQ line, the register must be read. During Transmit the
decoder is disabled, only bits B5 and B7 can be changed. During Receive only bit B6 can be changed, but
does not trigger the IRQ line immediately. The IRQ signal is set at the end of Transmit and Receive
phase.
66
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Table 6-44. IRQ Status Register (0x0C) for NFC and Card Emulation Operation
Function: Information available about TRF7970A IRQ and TX/RX status
Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read
phase. The reset also removes the IRQ flag.
Bit
Name
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of TX but the interrupt
request (IRQ = 1) is sent when TX is finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress. The flag is set at the
start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)
register
B4
Irq_err1
Protocol error
Any protocol error
B3
Irq_sdd
SDD completed
SDD (passive target at 106 kbps) successfully finished
B2
Irq_rf
RF field change
Sufficient RF signal level for operation was reached or lost
RF collision avoidance
finished
The system has finished collision avoidance and the minimum wait time is
elapsed.
RF collision avoidance not
finished successfully
The external RF field was present so the collision avoidance could not be
carried out.
B1
Irq_col
B0
Irq_col_err
Function
Description
6.14.3.3.2 Interrupt Mask Register (0x0D) and Collision Position Register (0x0E)
Table 6-45. Interrupt Mask Register (0x0D)
Default: 0x3E at POR = H and EN = L. Collision bits reset automatically after read operation.
Bit
Name
B7
Col9
Bit position of collision MSB Supports ISO14443A
Function
Description
B6
Col8
Bit position of collision
B5
En_irq_fifo
Interrupt enable for FIFO
Default = 1
B4
En_irq_err1
Interrupt enable for CRC
Default = 1
B3
En_irq_err2
Interrupt enable for Parity
Default = 1
B2
En_irq_err3
Interrupt enable for Framing
Default = 1
error or EOF
B1
En_irq_col
Interrupt enable for collision
error
Default = 1
B0
En_irq_noresp
Enables no-response
interrupt
Default = 0
Table 6-46. Collision Position Register (0x0E)
Function: Displays the bit position of collision or error
Default: 0x00 at POR = H and EN = L. Automatically reset after read operation.
Bit
Name
Function
Description
B7
Col7
Bit position of collision MSB
B6
Col6
B5
Col5
B4
Col4
B3
Col3
B2
Col2
B1
Col1
B0
Col0
ISO14443A mainly supported, in the other protocols this register shows the bit
position of error. Either frame, SOF/EOF, parity or CRC error.
Bit position of collision LSB
Detailed Description
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6.14.3.3.3 RSSI Levels and Oscillator Status Register (0x0F)
Table 6-47. RSSI Levels and Oscillator Status Register (0x0F)
Function: Displays the signal strength on both reception channels and RF amplitude during RF-off state. The RSSI values are valid from
reception start till start of next transmission.
Bit
Name
B7
Unused
Function
Description
B6
osc_ok
B5
rssi_x2
B4
rssi_x1
B3
rssi_x0
B2
rssi_2
MSB RSSI value of main
RX (RX_IN1)
B1
rssi_1
Main channel RSSI
B0
rssi_0
LSB RSSI value of main RX
(RX_IN1)
Crystal oscillator stable
indicator
13.56-MHz frequency stable (≈200 µs)
MSB RSSI value of auxiliary
Auxiliary channel is by default RX_IN2. The input can be swapped by B3 = 1
RX (RX_IN2)
(Chip State Control register 0x00). If "swapped", the Auxiliary channel is
Auxiliary channel RSSI
connected to RX_IN1 and, hence, the Auxiliary RSSI represents the signal level
MSB RSSI value of auxiliary at RX_IN2.
RX (RX_IN2)
Active channel is default and can be set with option bit B3 = 0 of chip state
control register 0x00.
RSSI measurement block is measuring the demodulated envelope signal (except in case of direct
command for RF amplitude measurement described later in direct commands section). The measuring
system is latching the peak value, so the RSSI level can be read after the end of receive packet. The
RSSI value is reset during next transmit action of the reader, so the new tag response level can be
measured. The RSSI levels calculated to the RF_IN1 and RF_IN2 are presented in Section 6.5.1.1 and
Section 6.5.1.2. The RSSI has 7 steps (3 bits) with 4-dB increment. The input level is the peak to peak
modulation level of RF signal measured on one side envelope (positive or negative).
6.14.3.3.4 Special Functions Register (0x10)
Table 6-48. Special Functions Register (0x10)
Function: User configurable options for ISO14443A specific operations
Bit
68
Name
Function
Description
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
par43
Disables parity checking for
ISO14443A
B4
next_slot_37us
B3
Sp_dir_mode
B2
4_bit_RX
B1
B0
0 = 18.88 µs
1 = 37.77 µs
Sets the time grid for next slot command in ISO15693
Bit stream transmit for
MIFARE at 106 kbps
Enables direct mode for transmitting ISO14443A data, bypassing the FIFO and
feeding the data bit stream directly onto the encoder.
0 = normal receive
1 = 4-bit receive
Enable 4-bit replay for example, ACK, NACK used by some cards; for example,
MIFARE Ultralight
14_anticoll
0 = anticollision framing
(0x93, 0x95, 0x97)
1 = normal framing (no
broken bytes)
Disable anticollision frames for 14443A (this bit should be set to 1 after
anticollision is finished)
col_7_6
0 = 7 subcarrier pulses
1 = 6 subcarrier pulses
Selects the number of subcarrier pulses that trigger collision error in the
14443A - 106 kbps
Detailed Description
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6.14.3.3.5 Special Functions Register (0x11)
Table 6-49. Special Functions Register (0x11)
Function: Indicate IRQ status for RX operations.
Bit
Name
Function
Description
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
Reserved
Reserved
B4
Reserved
Reserved
B3
Reserved
Reserved
B2
Reserved
Reserved
B1
Reserved
Reserved
B0
irg_srx
Copy of the RX start signal
(Bit 6) of the IRQ Status
Register (0x0C)
Signals the RX SOF was received and the RX is in progress. IRQ when RX is
completed.
6.14.3.3.6 Adjustable FIFO IRQ Levels Register (0x14)
Table 6-50. Adjustable FIFO IRQ Levels Register (0x14)
Function: Adjusts level at which FIFO indicates status by IRQ
Default: 0x00 at POR = H and EN = L
Bit
Name
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
Reserved
Reserved
B4
Reserved
Reserved
B3
Wlh_1
B2
Wlh_0
B1
Wll_1
B0
Wll_0
Function
Description
FIFO high IRQ level (during
RX)
Wlh_1
0
0
1
1
Wlh_0
0
1
0
1
IRQ Level
124
120
112
96
FIFO low IRQ level (during
TX)
Wll_1
0
0
1
1
Wll_0
0
1
0
1
IRQ Level
4
8
16
32
6.14.3.3.7 NFC Low Field Level Register (0x16)
Table 6-51. NFC Low Field Level Register (0x16)
Function: Defines level for RF collision avoidance
Default: 0x00 at POR = H and EN = L.
Bit
Name
B7
Clex_dis
Function
B6
Hash6
N/A
B5
Hash5
N/A
B4
Hash4
N/A
B3
Hash3
N/A
B2
Rfdet_I2
B1
Rfdet_I1
B0
Rfdet_I0
Disable clock extractor
RF field level for RF
collision avoidance
Description
NFC passive 106-kbps and ISO14443A card emulation
Comparator output is displayed in B6 of the NFC Target Protocol register
(0x19)
Detailed Description
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6.14.3.3.8 NFCID1 Number Register (0x17)
This register is used to hold the ID of the TRF7970A for use during card emulation and NFC peer-to-peer
target operations.
The procedure for writing the ID into register 0x17 is the following:
1. Write bits 5, 6, and 7 in register 0x18 to enable SDD anticollision (bit 5), and set bit 6 and 7 to select
the ID length of 4, 7, or 10 bytes.
2. Write the ID into register 0x17. This should be done using write continuous mode with 4, 7, or 10 bytes
(according to what was set in register 0x18 bits 6 and 7).
6.14.3.3.9 NFC Target Detection Level Register (0x18)
Table 6-52. NFC Target Detection Level Register (0x18)
Function: Defines level for RF wake up, enables automatic SDD and gives NFCID size. This register is supplied by Vin to ensure data
retention during complete power down.
Default: 0x00 at POR on Vin (not POR based on VDD_X) and not reset at EN = 0
Bit
B7
Name
Function
Description
Id_s1
NFCID1 size used in 106kbps passive target SDD
B6
B5
Id_s0
70
Id_s0
NFCID1 Size
(bytes)
0
0
4
0
1
7
1
0
10
1
1
Not allowed
Automatic SDD using internal state machine and ID stored in the NFCID1
Number register (0x17)
Sdd_en
B4
Id_s1
N/A
B3
Hi_rf
B2
Rfdet_h2
B1
Rfdet_h1
B0
Rfdet_h0
Extended range for RF
measurements
RF field level required for
system wakeup. If all bits
are 0, then the RF level
detection is off.
Comparator output is displayed in B7 of the NFC Target Protocol register
(0x19)
Detailed Description
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6.14.3.3.10 NFC Target Protocol Register (0x19)
This register is used (when read) to display the bit rate and protocol type when an NFC/RFID
Initiator/Reader is presented. An example use of this scenario would be when the TRF7970A is placed
into card emulation (Type A or Type B) and another TRF7970A or NFC device (polling for other NFC
devices) is presented to the TRF7970A in card emulation mode. The IRQ indicates that a field was
detected (IRQ Status = 0x04) or that Auto SDD has completed (IRQ Status = 0x08, if configured for
AutoSDD).
If Auto SDD is set and 0x04 is returned in IRQ status, then this register can be read out to see which
commands are coming in for gaining knowledge of the polling cycle sequence. Then, when the correct first
matching command (that is, REQA or REQB) is issued from Reader or Initiator, if AutoSDD is set, the IRQ
fires and the IRQ Status is 0x08, indicating completion of the SDD. The next IRQ should return 0x40 as
status, the Register 0x19 can be checked to make sure it is correct value (that is, 0xC9 for Type A at 106
kpbs or 0xC5 for Type B at 106 kbps) indicating there are bytes in the FIFO and a read of the FIFO status
indicates how many bytes to read out. For example, after AutoSDD is completed, there are four bytes in
the FIFO, and these should be the RATS command coming in from the reader, which the MCU controlling
the TRF7970A in Card Emulation mode must respond to. If AutoSDD is not set, as another example with
the TRF7970A in ISO14443B Card Emulation mode, then the field detect happens as previously described
and IRQs also fire to indicate RX is complete (0x40). This register must be checked and compared against
case statement structure that is set up for the value of this register to be 0xC5, indicating that an
ISO14443B command at 106 kbps was issued. When this register (0x19) is 0xC5, then the FIFO Status
can be read and should hold a value of 0x03, and when read, be the REQB command (0x05, 0x00, 0x00);
the controlling MCU must respond with the ATQB response. The next steps for either of these examples
follow the revelent portions of the ISO14443-3 or -4 standards, then the NFC Forum specifications,
depending on the system use case or application.
Table 6-53. NFC Target Protocol Register (0x19)
Function: Displays the bit rate and protocol type (active or passive) transmitted by initiator in first command. It also displays the comparator
outputs of both RF level detectors.
Default: 0x00 at POR = H and EN = L. B0 to B4 are automatically reset after MCU continuous read operation. B6 and B7 continuously
display the RF level comparator outputs.
Bit
Name
Function
Description
B7
Rf_h
RF level is above the wake- The wakeup level is defined by bits B0 to B2 in the NFC Target Detection Level
up level setting
register (0x18)
B6
Rf_l
RF level is above the RF
collision avoidance level
setting
The collision avoidance level is defined by bits B0 – B2 in the register 0x16
(NFC Low Field Detection Level)
B5
Reserved
Reserved
Reserved
1 = FeliCa
0 = ISO14443A
The first initiator command had physical level coding of FeliCa or ISO14443A
Passive target at 106 kbps
or transponder emulation
The first initiator/reader command was SENS_REQ or ALL_REQ
ISO14443B transponder
emulation
The first reader command was ISO14443B
Bit rate of first received
command
00
01
10
11
B4
FeliCa
B3
Pas_106
B2
Pas_14443B
B1
NFCBR1
B0
NFCBR0
= Reserved
= 106 kbps
= 212 kbps
= 424 kbps
Detailed Description
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6.14.3.4 Test Registers
6.14.3.4.1 Test Register (0x1A)
Table 6-54. Test Register (0x1A) (for Test or Direct Use)
Default: 0x00 at POR = H and EN = L.
Bit
Name
B7
OOK_Subc_In
Function
Description
B6
MOD_Subc_Out
B5
MOD_Direct
B4
o_sel
First stage output selection
B3
low2
Second stage gain -6 dB,
HP corner frequency/2
B2
low1
First stage gain -6 dB, HP
corner frequency/2
B1
zun
Input followers test
B0
Test_AGC
Subcarrier Input
OOK Pin becomes decoder digital input
Subcarrier Output
MOD Pin becomes receiver digitized subcarrier output
Direct TX modulation and
RX reset
MOD pin becomes input for TX modulation control by the MCU
o_sel = L: First stage output used for analog out and digitizing
o_sel = H: Second Stage output used for analog out and digitizing
AGC test, AGC level is
seen on rssi_210 bits
6.14.3.4.2 Test Register 0x1B
Table 6-55. Test Register (0x1B) (for Test or Direct Use)
Default: 0x00 at POR = H and EN = L. When a test_dec or test_io is set IC is switched to test mode. Test Mode persists until a stop
condition arrives. At stop condition the test_dec and test_io bits are cleared.
Bit
Name
Function
Description
B7
B6
B5
test_rf_level
RF level test
B4
72
B3
test_io1
B2
test_io0
I/O test
Not implemented
B1
test_dec
Decoder test mode
B0
clock_su
Coder clock 13.56 MHz
For faster test of coders
Detailed Description
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6.14.3.5 FIFO Control Registers
6.14.3.5.1 FIFO Status Register (0x1C)
Table 6-56. FIFO Status Register (0x1C)
Function: Number of bytes available to be read from FIFO (= N number of bytes, in hexadecimal)
Bit
Name
B7
Foverflow
Function
B6
Fb6
FIFO bytes fb[6]
B5
Fb5
FIFO bytes fb[5]
B4
Fb4
FIFO bytes fb[4]
B3
Fb3
FIFO bytes fb[3]
B2
Fb2
FIFO bytes fb[2]
B1
Fb1
FIFO bytes fb[1]
B0
Fb0
FIFO bytes fb[0]
FIFO overflow error
Description
Bit is set when FIFO has more than 127 bytes presented to it
Bits B0:B6 indicate how many bytes that are in the FIFO to be read out (= N
number of bytes, in hex)
Detailed Description
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6.14.3.5.2 TX Length Byte1 Register (0x1D), TX Length Byte2 Register (0x1E)
Table 6-57. TX Length Byte1 Register (0x1D)
Function: High 2 nibbles of complete, intended bytes to be transferred through FIFO
Register default is set to 0x00 at POR and EN = 0. It is also automatically reset at TX EOF
Bit
Name
Function
Description
B7
Txl11
Number of complete byte
bn[11]
B6
Txl10
Number of complete byte
bn[10]
B5
Txl9
Number of complete byte
bn[9]
B4
Txl8
Number of complete byte
bn[8]
B3
Txl7
Number of complete byte
bn[7]
B2
Txl6
Number of complete byte
bn[6]
B1
Txl5
Number of complete byte
bn[5]
B0
Txl4
Number of complete byte
bn[4]
High nibble of complete, intended bytes to be transmitted
Middle nibble of complete, intended bytes to be transmitted
Table 6-58. TX Length Byte2 Register (0x1E)
Function: Low nibbles of complete bytes to be transferred through FIFO; Information about a broken byte and number of bits to be
transferred from it
Default: 0x00 at POR and EN = 0. It is also automatically reset at TX EOF
Bit
74
Name
Function
Description
B7
Txl3
Number of complete byte
bn[3]
B6
Txl2
Number of complete byte
bn[2]
B5
Txl1
Number of complete byte
bn[1]
B4
Txl0
Number of complete byte
bn[0]
B3
Bb2
Broken byte number of bits
bb[2]
B2
Bb1
Broken byte number of bits
bb[1]
B1
Bb0
Broken byte number of bits
bb[0]
B0
Bbf
Broken byte flag
Low nibble of complete, intended bytes to be transmitted
Number of bits in the last broken byte to be transmitted.
It is taken into account only when broken byte flag is set.
B0 = 1, indicates that last byte is not complete 8 bits wide.
Detailed Description
Copyright © 2011–2014, Texas Instruments Incorporated
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SLOS743K – AUGUST 2011 – REVISED APRIL 2014
7 Application Schematic and Layout Considerations
7.1
TRF7970A Reader System Using Parallel Microcontroller Interface
7.1.1
General Application Considerations
Figure 7-1 shows the most flexible TRF7970A application schematic. Both ISO15693, ISO14443 and
FeliCa systems can be addressed. Due to the low clock frequency on the DATA_CLK line, the parallel
interface is the most robust way to connect the TRF7970A with the MCU.
Figure 7-1 shows matching to a 50-Ω port, which allows connecting to a properly matched 50-Ω antenna
circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).
7.1.2
Schematic
Figure 7-1 shows a sample application schematic for a parallel MCU interface.
OSC_OUT
2
C23
1
27pF
OSC_IN
0.01uF
2.2uF 0.01uF
GND
GND
R2 0
C11
C10 8 C
27pF 100pF 220pF
GND GND
C9
C2
1500pF
L2
L1
330nH
150nH
C7
C4
1200pF
680pF
GND
C5
680pF
1200pF
1500pF
C3
GND
1
2
3
4
5
6
7
8
EN
SYS_CLK
DATA_CLK
VIN
VDD_X
OSC_IN
OSC_OUT
VDD_A
VIN
VDD_RF
VDD_PA
TX_OUT
VSS_PA
VSS_RX
RX_IN1
TRF7970A
33
GND(PAD)
GND
GND
GND
C21
0.01uF
TP
40
GND
I/O_7
I/O_6
I/O_5
I/O_4
I/O_3
I/O_2
I/O_1
I/0_0
VCC 39
RST_NMI
TCK
TMS
TDI
24 TDO/TDI
23
22
21
20
19
18
17
TXD
RXD
DATA_CLK
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
TCK
TMS
P4.7/TBCLK
P4.6/TBOUTH/ACLK
P4.5/TB2
P4.4/TB1
P4.3/TB0
P4.2/TB2
P4.1/TB1
P4.0/TB0
X4
X4
X4
X4
X4
X
X
1 VCC
2 SYS_CLK
R5
3
47k
4
EN
5
RST_NMI
6
R6
C1
7
10k
0.1uF
8
9
GND
10
11
12
MOD
13
IRQ
14
ASK/OOK
15
16
GND
17
18
19
20
VDD_X
GND
ASK/OOK
IRQ
MOD
9
10
11
12
13
14
15
16
GND
2.2uF
2.2uF
C6 10pF
R3 0
C12
12pF
2.2uF
GND
GND
C13
12pF
R1
C14
68pF 6.8k
0.01uF
C20
C25
GND
MC-921
L3
1.5uH
GND
32
31
30
29
28
27
26
25
X2
C18
C17
JTAG
057-014-2
TDO/TDI X4-1 -2 VCC
TDI
X4-3 -4
TMS
X4-5 -6
TCK
X4-7 -8
GND
X4-9 -10
RST_NMI X4-11 4-12
C24 27pF
VDD_X
OSC_IN
OSC_OUT
VSS_D
EN
SYS_CLK
DATA_CLK
EN2
0.01uF
C16
4
RX_IN2
VSS
BAND_GAP
ASK/OOK
IRQ
MOD
VSS_A
VDD_I/O
C26
C19
C15
GND2
X4-13 4-14
SMA-142-0701-801/806
X3
(+2.7VDC - 5.5VDC)
VIN
GND
IN
3
GND
R4 100R
VCC
GND1 OUT
GND
C22
2.2uF
GND
Figure 7-1. Application Schematic – Parallel MCU Interface
An MSP430F2370 (32KB Flash, 2KB RAM) is shown in Figure 7-1. Minimum MCU requirements depend
on application requirements and coding style. If only one ISO protocol or a limited command set of a
protocol needs to be supported, MCU Flash and RAM requirements can be significantly reduced. Be
aware that recursive inventory and anticollision commands require more RAM than single slotted
operations. For example, current reference firmware for ISO15693 (with host interface) is approximately
8KB, using 512B RAM; for all supported protocols (also with same host interface) the reference firmware
is approximately 12KB and uses a minimum of 1KB RAM. An MCU capable of running its GPIOs at
13.56 MHz is required for Direct Mode 0 operations.
Copyright © 2011–2014, Texas Instruments Incorporated
Application Schematic and Layout Considerations
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7.2
www.ti.com
TRF7970A Reader System Using SPI With SS Mode
7.2.1
General Application Considerations
Figure 7-2 shows the TRF7970A application schematic optimized for both ISO15693 and ISO14443
systems using the Serial Port Interface (SPI). Short SPI lines, proper isolation of radio frequency lines,
and a proper ground area are essential to avoid interference. The recommended clock frequency on the
DATA_CLK line is 2 MHz.
Figure 7-2 shows matching to a 50-Ω port, which allows connecting to a properly matched 50-Ω antenna
circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).
7.2.2
Schematic
Figure 7-2 shows a sample application schematic for SPI with an SS mode MCU interface.
OSC_OUT
2
GND1 OUT
C23
1
27pF
OSC_IN
GND
GND
GND
C6 10pF
C13
12pF
C11
C10 8 C
27pF 100pF 220pF
GND GND
C9
330nH
L1
C7
C4
680pF
150nH
1200pF
GND
C5
1200pF
680pF
1500pF
C3
GND
1
2
3
4
5
6
7
8
VDD_A
VIN
VDD_RF
VDD_PA
TX_OUT
VSS_PA
VSS_RX
RX_IN1
TRF7970A
33
GND(PAD)
GND
I/O_7
I/O_6
I/O_5
I/O_4
I/O_3
I/O_2
I/O_1
I/0_0
GND
C21
0.01uF
24
23
22
21
20
19
18
17
RST_NMI
TCK
TMS
TDI
TDO/TDI
P3.1
P3.2
P3.7
P3.0
P3.6
P4.2
P4.2
VDD_X
GND
TXD
RXD
DATA_CLK
TP
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
TCK
TMS
P4.7/TBCLK
P4.6/TBOUTH/ACLK
P4.5/TB2
P4.4/TB1
P4.3/TB0
P4.2/TB2
P4.1/TB1
P4.0/TB0
X4
X4
X4
X4
X4
X
X
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
VCC
SYS_CLK
EN
R6
10k
R5
47k
RST_NMI
C1
0.1uF
GND
MOD
IRQ
ASK/OOK
VCC
P3.0
P3.1
P3.2
VDD_X
GND
ASK/OOK
IRQ
MOD
GND
VCC
GND
9
10
11
12
13
14
15
16
GND
C2
1500pF
L2
R3 0
R2 0
C12
12pF
2.2uF
GND
MC-921
R1
C14
68pF 6.8k
0.01uF
2.2uF
VDD_X
OSC_IN
OSC_OUT
VSS_D
EN
SYS_CLK
DATA_CLK
EN2
2.2uF 0.01uF
0.01uF
L3
1.5uH
C18
C17
32
31
30
29
28
27
26
25
2.2uF
GND
RX_IN2
VSS
BAND_GAP
ASK/OOK
IRQ
MOD
VSS_A
VDD_I/O
X2
C16
C20
EN
SYS_CLK
DATA_CLK
VIN
C25
VDD_X
OSC_IN
OSC_OUT
X4-13 4-14
C26
C19
C15
C24 27pF
GND
0.01uF
GND
GND2
4
GND
R4 100R
VCC
SMA-142-0701-801/806
(+2.7VDC - 5.5VDC)
X3
VIN
IN
JTAG
057-014-2
TDO/TDI X4-1 -2 VCC
TDI
X4-3 -4
TMS
X4-5 -6
TCK
X4-7 -8
GND
X4-9 -10
RST_NMI X4-11 4-12
3
GND
C22
2.2uF
GND
Figure 7-2. Application Schematic – SPI With SS Mode MCU Interface
An MSP430F2370 (32KB Flash, 2KB RAM) is shown in Figure 7-2. Minimum MCU requirements depend
on application requirements and coding style. If only one ISO protocol or a limited command set of a
protocol needs to be supported, MCU Flash and RAM requirements can be significantly reduced and user
should be aware that recursive inventory and anticollision commands require more RAM than single
slotted operations. For example, current reference firmware for ISO15693 (with host interface) is
approximately 8KB, using 512B RAM and for all supported protocols (also with same host interface) the
reference firmware is approximately 12KB and uses a minimum of 1KB RAM. An MCU capable of running
its GPIOs at 13.56 MHz is required for Direct Mode 0 operations.
76
Application Schematic and Layout Considerations
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Copyright © 2011–2014, Texas Instruments Incorporated
TRF7970A
www.ti.com
7.3
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Layout Considerations
Keep all decoupling capacitors as close to the IC as possible, with the high-frequency decoupling
capacitors (10 nF) closer than the low-frequency decoupling capacitors (2.2 µF).
Place ground vias as close as possible to the ground side of the capacitors and reader IC pins to minimize
possible ground loops.
It is not recommend to use any inductor sizes below 0603, as the output power can be compromised. If
smaller inductors are necessary, output performance must be confirmed in the final application.
Pay close attention to the required load capacitance of the crystal, and adjust the two external shunt
capacitors accordingly. Follow the recommendations of the crystal manufacturer for those values.
There should be a common ground plane for the digital and analog sections. The multiple ground sections
or islands should have vias that tie the different sections of the planes together.
Ensure that the exposed thermal pad at the center of the reader IC is properly laid out. It should be tied to
ground to help dissipate any heat from the package.
All trace line lengths should be made as short as possible, particularly the RF output path, crystal
connections, and control lines from the reader to the microprocessor. Proper placement of the TRF7970A,
microprocessor, crystal, and RF connection or connector help facilitate this.
Avoid crossing of digital lines under RF signal lines. Also, avoid crossing of digital lines with other digital
lines when possible. If the crossings are unavoidable, 90° crossings should be used to minimize coupling
of the lines.
Depending on the production test plan, consider possible implementations of test pads or test vias for use
during testing. The necessary pads or vias should be placed in accordance with the proposed test plan to
enable easy access to those test points.
If the system implementation is complex (for example, if the RFID reader module is a subsystem of a
greater system with other modules (Bluetooth, WiFi, microprocessors, and clocks), special considerations
should be taken to ensure that there is no noise coupling into the supply lines. If needed, special filtering
or regulator considerations should be used to minimize or eliminate noise in these systems.
For more information/details on layout considerations, see the TRF796x HF-RFID Reader Layout Design
Guide (SLOA139).
7.4
Impedance Matching TX_Out (Pin 5) to 50 Ω
The output impedance of the TRF7970A when operated at full power out setting is nominally 4 + j0 (4 Ω
real). This impedance must be matched to a resonant circuit and TI recommends matching circuit from
4 Ω to 50 Ω, as commercially available test equipment (for example, spectrum analyzers, power meters,
and network analyzers) are 50-Ω systems. An impedance-matching reference circuit can be seen in
Figure 7-3 and Figure 7-4. This section explains how the values were calculated.
Starting with the 4-Ω source, the process of going from 4 Ω to 50 Ω can be represented on a Smith Chart
simulator (available from http://www.fritz.dellsperger.net/). The elements are combined where appropriate
(see Figure 7-3).
Copyright © 2011–2014, Texas Instruments Incorporated
Application Schematic and Layout Considerations
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TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
www.ti.com
Figure 7-3. Impedance Matching Circuit
This yields the Smith Chart Simulation shown in Figure 7-4.
Figure 7-4. Smith Chart Simulation
78
Application Schematic and Layout Considerations
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Copyright © 2011–2014, Texas Instruments Incorporated
TRF7970A
www.ti.com
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Resulting power out can be measured with a power meter or spectrum analyzer with power meter function
or other equipment capable of making a "hot" measurement. Observe maximum power input levels on test
equipment and use attenuators whenever available to avoid damage to equipment. Expected output
power levels under various operating conditions are shown in Table 6-25.
7.5
Reader Antenna Design Guidelines
For HF antenna design considerations using the TRF7970A, see these documents:
• Antenna Matching for the TRF7960 RFID Reader (SLOA135)
• TRF7960TB HF RFID Reader Module User's Guide (SLOU297)
Copyright © 2011–2014, Texas Instruments Incorporated
Application Schematic and Layout Considerations
Submit Documentation Feedback
Product Folder Links: TRF7970A
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TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
www.ti.com
8 Device and Documentation Support
8.1
Documentation Support
The following documents describe the TRF7970A device. Copies of these documents are available on the
Internet at www.ti.com.
SLOZ011
8.2
TRF7970A Silicon Errata. Describes the known exceptions to the functional specifications
for the TRF7970A.
Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the
respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views;
see TI's Terms of Use.
TI E2E Community
TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At
e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow
engineers.
8.3
Trademarks
MSP430 is a trademark of Texas Instruments.
ARM is a registered trademark of ARM Limited.
Bluetooth is a registered trademark of Bluetooth SIG.
MIFARE is a trademark of NXP Semiconductors.
FeliCa is a trademark of Sony Corporation.
Wi-Fi is a registered trademark of Wi-Fi Alliance.
All other trademarks are the property of their respective owners.
8.4
Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
8.5
Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms and definitions.
9 Mechanical Packaging and Orderable Information
9.1
Packaging Information
The following pages include mechanical packaging and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and
revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
80
Mechanical Packaging and Orderable Information
Submit Documentation Feedback
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Copyright © 2011–2014, Texas Instruments Incorporated
PACKAGE OPTION ADDENDUM
www.ti.com
4-Apr-2014
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
TRF7970ARHBR
ACTIVE
VQFN
RHB
32
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TRF
7970A
TRF7970ARHBT
ACTIVE
VQFN
RHB
32
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TRF
7970A
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
4-Apr-2014
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
15-Jan-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
TRF7970ARHBR
VQFN
RHB
32
3000
330.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
TRF7970ARHBT
VQFN
RHB
32
250
180.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
15-Jan-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
TRF7970ARHBR
VQFN
RHB
32
3000
367.0
367.0
35.0
TRF7970ARHBT
VQFN
RHB
32
250
210.0
185.0
35.0
Pack Materials-Page 2
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