AS8267 / AS8268
Single-Phase 2-Current Energy Measurement Integrated Circuits
with Microcontroller, RTC, Programmable Multi-Purpose I/Os,
LCD Driver and On-Chip FLASH Memory
1. Key Features
-
Precision single-phase, one or two current input
energy measurement front-end including SigmaDelta modulators for A/D-conversion and digital
signal processor (DSP).
-
Low current consumption of 5mA, depending on
MCU activity.
-
Digital phase correction and selectable gain on
both current channels for use with two current
transformers (CT) or one CT and one shunt.
-
Power-supply monitor (PSM) for power-on reset
and reset when the supply voltage falls below a
defined threshold.
-
Customer programmable 8-bit 8051 compatible
microcontroller (MCU).
-
Programmable MCU clock for optional low
power operating conditions.
-
Highly reliable 32kBytes of non-volatile Flash
memory is provided on-chip for storage of both
program and data.
-
Program and data security is provided by
optional password and attack counter
protection.
-
2 x Universal Asynchronous Receiver /
Transmitters (UART) for external
communications such as programme download
and debugging.
-
Programmable watchdog timer (WDT) and
external system reset pin.
-
Real-time clock/calendar (RTC) with on-chip
digital calibration and separate battery supply
pin.
-
On-chip temperature sensor for optional
temperature compensation.
-
On-chip voltage reference (VREF) with small
temperature coefficient (15ppm/K typ.).
-
Low power 3.0 – 4.0MHz crystal oscillator.
-
SPI compatible interface for optional external
non-volatile EEPROM memory selectable up to
32kBytes.
Revision 1.0, 19-Jun-07
DATA SHEET
-
Mains current lead/lag status indication for
reactive energy measurement.
-
Low power battery operating mode for meter
reading when Mains voltage is not present.
-
AS8267: 20 x 4 segment LCDD
9 x multi-purpose I/O (MPIO)
-
AS8268: 24 x 4 segment LCDD
12 x multi-purpose I/O (MPIO)
2. General Description
The AS8267 / AS8268 are highly integrated CMOS
single-phase energy metering devices for fully
electronic LCD meter systems. The AS8267 /
AS8268 have been designed to ensure a meters
full compliance with the international Standards
IEC62052 and ANSI.
The AS8267 / AS8268 ICs include all the functions
required for conventional 1 current or 2-current
anti-tamper meters. The functions include precision
energy measurement, an 8-bit microcontroller unit
(MCU) with 32kBytes of Flash memory, an on-chip
Liquid Crystal Display driver (LCDD),
programmable multi-purpose Inputs/Outputs
(MPIO), a real time clock/calendar (RTC) for
complex tariff functions such as time-of-use or
maximum demand billing and a Serial Peripheral
Interface (SPI) for reading data from and writing
data to an optional external non-volatile memory
(EEPROM).
The AS8267 / AS8268 ICs have a dedicated energy
measurement front-end, which includes an analog
front-end and programmable Digital Signal
Processor (DSP) from which active energy, mains
voltage and mains current are provided. Reactive
and apparent energy can also be calculated.
The on-chip 8-bit 8051 compatible microcontroller
is freely programmable and provides user access to
the various functional blocks. The dedicated
Universal Asynchronous Receiver / Transmitter
(UART1) in the System Control block allows access
to various system functions and blocks. A second
UART (UART2) is also provided, which may for
example be used for debugging. The on-chip
memory includes 32kByte of highly reliable nonvolatile Flash program (and data) memory and
Page 1 of 136
Data Sheet AS8267 / AS8268
1kByte volatile data memory. The meter system
designer also has the option of an additional
external EEPROM memory, which is selectable in
size from 1kByte to 32kByte (in binary steps).
Program and data stored in the on-chip non-volatile
Flash memory can be secured by password
protection, in addition to an attack counter which
‘locks’ access after 5 unauthorised attacks.
An on-chip programmable watchdog timer (WDT) is
available to automatically initiate a system reset if
a regular ‘hold-off’ signal is not detected.
The system timing and real time clock (RTC) has a
dedicated external battery supply pin (VDD_BAT),
enabling the oscillator and RTC to continue
operation during ‘power-down’. The RTC may be
digitally calibrated for oscillator frequency
accuracy.
The on-chip temperature sensor provides the meter
designer the option of temperature compensation
for any of the measured parameters or functional
blocks provided, over the full operating temperature
range of the device.
particularly in the case where scrolled display data
is required.
The programmable multi-purpose I/O pins (MPIO)
may be independently configured as inputs or
outputs. All the I/O pins are programmable for data
direction, pull-up/pull-down resistors and drive
strength (4mA/8mA). Typical functions may include
LED energy consumption pulse output, energy
direction and fault condition indication depending
on current 1 or current 2 being active for the
energy calculation, push button for display
scrolling, mains isolation relay control for
prepayment meters, optical interface etc.
An on-chip analog ground buffer (ABUF) and
voltage reference (VREF) ensures that no external
circuitry is required. A power-supply monitor (PSM)
provides a reset, when VDD falls below a safe
operating threshold.
A reset pin (RES_N) is available for external
system reset.
The AS8267 / AS8268 ICs are available in LQFP64
plastic package.
The LCD Driver (LCDD) block enables the display
of information provided by the microcontroller,
directly to the LCD. Two dedicated data register
banks are provided to simplify programming,
Revision 1.0, 19-Jun-07
Page 2 of 136
Data Sheet AS8267 / AS8268
3. Typical Application Circuit
3.3V
+
3.3V
LCD
kWh
Vrms
Irms
+
VDDA
33
7
32
VDD_BAT 31
Low
Power
Oscillator
VDDD
22
37 38 39 40
13
Low
Power
Divider
RTC
System Timing & RTC
LOAD
Analog Front End
I1P
3
I1N
4
I2N
6
I2P
5
VP
1
VN
2
LCD
Driver
SDM
DSP
SDM
MCU
SDM
RES_N
34
Multipurpose
I/Os
WDT
Temperature
Sensor
FLASH
Memory
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
LSD0
LSD1
LSD2
LSD3
LSD4
LSD5
LSD6
LSD7
LSD8
LSD9
LSD10
LSD11
LSD12
LSD13
LSD14
LSD15
LSD16
LSD17
LSD18
LSD19
LSD20
LSD21
LSD22
LSD23
AS8268 only
XIN XOUT
LBP0
LBP1
LBP2
LBP3
3.3V
9
IO0
LED
10
IO1
DIRO
11
IO2
FAULT
12
15
16
17
18
19
26
27
28
IO3
IO4
IO5
IO6
IO7
IO8
IO9
IO10
IO11
23
20
24
25
S_N
MISO
MOSI
SC
I/Os
Examples
only
Push-Button
Reference pulses
for calibration
UART1
29
TXD
30
RXD
SPI
8
VSSA
14
VSSD
21
VSSD
S 1
Q
2
3.3V W 3
VSS
VI
+
N
Figure 1:
VO
4
EEPROM
AS8268 only
System
Control
8 VCC 3.3V
HOLD 3.3V
7
6 C
5 D
3.3V
GND
L
Typical application circuit of the AS8267 / AS8268
Revision 1.0, 19-Jun-07
Page 3 of 136
Data Sheet AS8267 / AS8268
LSD16
LSD15
LSD14
LSD13
LSD12
LSD11
LSD10
LSD9
LSD8
56
55
54
53
52
51
50
49
LSD8
49
LSD17
LSD9
50
57
LSD10
51
LSD18
LSD11
52
58
LSD12
53
LSD19
LSD13
54
59
LSD14
55
LSD20
LSD15
56
60
LSD16
57
LSD21
LSD17
58
61
LSD18
59
LSD22
LSD19
60
62
n.c.
61
LSD23
n.c.
62
63
n.c.
63
64
n.c.
64
4. Pin Out
VP
1
48
LSD7
VP
1
48
LSD7
VN
2
47
LSD6
VN
2
47
LSD6
I1P
3
46
LSD5
I1P
3
46
LSD5
I1N
4
45
LSD4
I1N
4
45
LSD4
I2P
5
44
LSD3
I2P
5
44
LSD3
I2N
6
43
LSD2
I2N
6
43
LSD2
VDDA
7
42
LSD1
VDDA
7
42
LSD1
VSSA
8
41
LSD0
VSSA
8
41
LSD0
IO0
9
40
LBP3
IO0
9
40
LBP3
IO1
10
39
LBP2
IO1
10
39
LBP2
IO2
11
38
LBP1
IO2
11
38
LBP1
IO3
12
37
LBP0
IO3
12
37
LBP0
VDDD
13
36
n.c.
VDDD
13
36
n.c.
VSSD
14
35
n.c.
VSSD
14
35
n.c.
IO4
15
34
RES_N
IO4
15
34
RES_N
IO5
16
33
XOUT
IO5
16
33
XOUT
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
IO7
IO8
MISO
VSSD
VDDD
S_N
MOSI
SC
IO9
IO10
IO11
TXD
RXD
VDD_BAT
XIN
32
XIN
AS8268
LQFP64
IO6
31
26
n.c.
VDD_BAT
25
SC
30
24
MOSI
RXD
23
S_N
29
22
VDDD
TXD
21
VSSD
28
20
MISO
n.c.
19
IO8
27
18
IO7
n.c.
17
IO6
AS8267
LQFP64
5. Pin Description
Pin
No.
Pin Name Pin Name
AS8267
AS8268
Type
Description
1
VP
VP
AI
Positive input for the voltage channel. VP is a differential input with VN. The
typical differential voltage is ±100mV peak.
2
VN
VN
AI
Negative input for the voltage channel. VN is a differential input with VP.
3
I1P
I1P
AI
Positive input for the first current channel. I1P is a differential input with I1N.
The input gain is programmable depending on the desired current sensor. The
typical differential voltage is ±150mV peak (Gain = 4).
4
I1N
I1N
AI
Negative input for the first current channel. I1N is a differential input with I1P.
The input gain is programmable depending on the desired current sensor. The
typical differential voltage is ±150mV peak (Gain = 4).
5
I2P
I2P
AI
Positive input for the second current channel. I2P is a differential input with
I2N. The input gain is programmable depending on the desired current sensor.
The typical differential voltage is ±150mV peak
(Gain = 4).
6
I2N
I2N
AI
Negative input for the second current channel. I2N is a differential input with
I2P. The input gain is programmable depending on the desired current sensor.
The typical differential voltage is ±150mV peak
(Gain = 4).
7
VDDA
VDDA
S
Positive supply voltage for the analog circuitry. The required supply voltage is
3.3V ±10%.
8
VSSA
VSSA
S
Ground reference for the analog circuitry.
9
IO0
IO0
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
10
IO1
IO1
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Revision 1.0, 19-Jun-07
Page 4 of 136
Data Sheet AS8267 / AS8268
Pin
No.
Pin Name Pin Name
AS8267
AS8268
Type
Description
11
IO2
IO2
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
12
IO3
IO3
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
13
VDDD
VDDD
S
Positive supply voltage to the digital circuitry and is internally connected to pin
22. The required supply voltage is 3.3V ±10%.
14
VSSD
VSSD
S
Ground reference for the digital circuitry.
15
IO4
IO4
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
16
IO5
IO5
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
17
IO6
IO6
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
18
IO7
IO7
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
19
IO8
IO8
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
20
MISO
MISO
21
VSSD
VSSD
S
Ground reference for the digital circuitry.
22
VDDD
VDDD
S
Positive digital supply. VDDD provides the positive supply voltage to the digital
circuitry and is internally connected to pin 13. The required supply voltage is
3.3V ±10%.
23
S_N
S_N
DIOPU Serial peripheral interface (SPI): Chip select
24
MOSI
MOSI
DIOPD Serial peripheral interface (SPI):
Serial Data output in Master mode
Serial Data input in Slave mode
25
SC
SC
26
n.c.
IO9
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
27
n.c.
IO10
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
28
n.c.
IO11
DIO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
29
TXD
TXD
DO
Universal Asynchronous Receiver/Transmitter (UART1) serial transmit data
output.
30
RXD
RXD
DIPU
Universal Asynchronous Receiver/Transmitter (UART1) serial receive data
input.
31
VDD_BAT VDD_BAT
DIOPD Serial peripheral interface (SPI):
Serial Data input in Master mode
Serial Data output in Slave mode
DIOPU Serial peripheral interface (SPI): Serial clock
S
Battery backup supply voltage input for the real time clock (RTC).
32
XIN
XIN
AI
A 3.0 to 4.0MHz crystal may be connected across XIN and XOUT.
Alternatively, an external clock signal may be applied to XIN.
33
XOUT
XOUT
AO
See XIN above, for the connection of a crystal. When an external clock is
applied to XIN, XOUT is not connected.
34
RES_N
RES_N
35
n.c.
n.c.
Revision 1.0, 19-Jun-07
System reset active low.
Not connected
Page 5 of 136
Data Sheet AS8267 / AS8268
Pin
No.
Pin Name Pin Name
AS8267
AS8268
Type
Description
36
n.c.
n.c.
Not connected
37
LBP0
LBP0
AO
LCD back-plane driver output signal.
38
LBP1
LBP1
AO
LCD back-plane driver output signal.
39
LBP2
LBP2
AO
LCD back-plane driver output signal.
40
LBP3
LBP3
AO
LCD back-plane driver output signal.
41
LSD0
LSD0
AO
LCD segment driver output signal.
42
LSD1
LSD1
AO
LCD segment driver output signal.
43
LSD2
LSD2
AO
LCD segment driver output signal.
44
LSD3
LSD3
AO
LCD segment driver output signal.
45
LSD4
LSD4
AO
LCD segment driver output signal.
46
LSD5
LSD5
AO
LCD segment driver output signal.
47
LSD6
LSD6
AO
LCD segment driver output signal.
48
LSD7
LSD7
AO
LCD segment driver output signal.
49
LSD8
LSD8
AO
LCD segment driver output signal.
50
LSD9
LSD9
AO
LCD segment driver output signal.
51
LSD10
LSD10
AO
LCD segment driver output signal.
52
LSD11
LSD11
AO
LCD segment driver output signal.
53
LSD12
LSD12
AO
LCD segment driver output signal.
54
LSD13
LSD13
AO
LCD segment driver output signal.
55
LSD14
LSD14
AO
LCD segment driver output signal.
56
LSD15
LSD15
AO
LCD segment driver output signal.
57
LSD16
LSD16
AO
LCD segment driver output signal.
58
LSD17
LSD17
AO
LCD segment driver output signal.
59
LSD18
LSD18
AO
LCD segment driver output signal.
60
LSD19
LSD19
AO
LCD segment driver output signal.
61
n.c.
LSD20
AO
LCD segment driver output signal.
62
n.c.
LSD21
AO
LCD segment driver output signal.
63
n.c.
LSD22
AO
LCD segment driver output signal.
64
n.c.
LSD23
AO
LCD segment driver output signal.
Note: Shaded pins above only available with AS8268 IC
PIN Types:
S
AI
AO
DIPU
DO
DIO
DIOPD
DIOPU
Revision 1.0, 19-Jun-07
Supply pin
Analog Input pin
Analog Output pin
Digital Input pin with pull-up resistor
Digital Output pin
Programmable Digital Input or Output pin
Digital Input or Output pin with pull-down resistor
Digital Input or Output pin with pull-up resistor
Page 6 of 136
Data Sheet AS8267 / AS8268
Table of Contents
1.
Key Features .........................................................................................................................................1
2.
General Description ...............................................................................................................................1
3.
Typical Application Circuit ......................................................................................................................3
4.
Pin Out..................................................................................................................................................4
5.
Pin Description ......................................................................................................................................4
6.
Electrical Characteristics........................................................................................................................8
6.1
Absolute Maximum Ratings (Non-Operating) ......................................................................................8
6.2
Operating Conditions ........................................................................................................................8
6.3
DC/AC Characteristics for Digital Inputs and Outputs..........................................................................9
6.4
Electrical System Specification ........................................................................................................ 10
7.
Performance Graphs ............................................................................................................................ 12
8.
Detailed Functional Description ............................................................................................................ 15
8.1
Energy Measurement Front End (Including DSP) .............................................................................. 17
8.2
Temperature Sensor ....................................................................................................................... 50
8.3
LCD Driver (LCDD) ......................................................................................................................... 52
8.4
Programmable Multi-Purpose I/Os (MPIO) ........................................................................................ 57
8.5
Serial Peripheral Interface (SPI) ...................................................................................................... 67
8.6
External EEPROM Requirements ..................................................................................................... 78
8.7
FLASH Memory............................................................................................................................... 83
8.8
8051 Microcontroller (MCU) ............................................................................................................. 90
8.9
System Control (SCT) ................................................................................................................... 110
8.10 Serial Interface – UART1 ............................................................................................................... 118
9.
Circuit Diagram.................................................................................................................................. 127
10. Parts List........................................................................................................................................... 128
11. Packaging ......................................................................................................................................... 130
12. Product Ordering Guide ..................................................................................................................... 130
13. Collection of Formulae ....................................................................................................................... 131
14. Terminology ...................................................................................................................................... 135
15. Revision ............................................................................................................................................ 136
16. Copyright .......................................................................................................................................... 136
17. Disclaimer ......................................................................................................................................... 136
18. Contact ............................................................................................................................................. 136
Revision 1.0, 19-Jun-07
Page 7 of 136
Data Sheet AS8267 / AS8268
6. Electrical Characteristics
6.1
Absolute Maximum Ratings (Non-Operating)
Stresses beyond the ‘Absolute Maximum Ratings’ may cause permanent damage to the AS8267 / AS8268 ICs.
These are stress ratings only. Functional operation of the device at these or any other conditions beyond those
indicated under ‘Operating Conditions’ is not implied.
Caution: Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameter
Symbol
Min
Max
VDD
-0.3
+5.0
V
Vin
-0.3
VDD+0.3
V
1000
V
125
°C
DC supply voltage
Input pin voltage
Electrostatic discharge
ESD
Storage temperature
Tstrg
Lead temperature profile
Tlead
-55
Norm: MIL 883 E method 3015
Norm: IPC/JEDEC-020C
Humidity non-condensing
6.2
Unit Notes
5
85
%
Operating Conditions
Parameter
Symbol
Min
Typ
Max
Unit
Positive analog supply voltage
VDDA
3.0
3.3
3.6
V
Negative analog supply voltage
VSSA
0
0
V
Difference of supplies
A-D
-0.1
0.1
V
Positive digital supply voltage
VDDD
3.0
3.6
V
Negative digital supply voltage
VSSD
0
0
V
Battery supply voltage
VDD_BAT
2.0
3.3
3.6
V
Ambient temperature
Tamb
-40
25
85
°C
Supply current
Isupp
System clock frequency
fosc
Revision 1.0, 19-Jun-07
3.3
5
3.0
3.579545
mA
4.0
Notes
VDDA – VDDD
VSSA – VSSD
Depending on MCU activity
MHz
Page 8 of 136
Data Sheet AS8267 / AS8268
6.3
DC/AC Characteristics for Digital Inputs and Outputs
CMOS Input with Schmitt Trigger and Pull-up Resistor (RXD, RES_N)
Parameter
Symbol
Min
High level input voltage
VIH
0.7 x VDD
Low level input voltage
VIL
Low level input current
IIL
-100
Symbol
Min
High level output voltage
VOH
2.5
Low level output voltage
Typ
Max
Unit
Notes
V
0.3 x VDD
V
-15
µA
Max
Unit
V
Tested at VDD=3.0V
VOL
0.4
V
Tested at VDD=3.0V
High level output current
IOH
4
mA
Tested at VDD=3.0V and Vout=VOH
Low level output current
IOL
mA
Tested at VDD=3.0V and Vout=VOL
Tested at VDD=3.6V and Vin=0V
CMOS Output (TXD)
Parameter
Typ
-4
Notes
MPIO Inputs with Pull-up or Pull-down Resistor (SC, S_N, MISO, MOSI)
Parameter
Symbol
Min
High level input voltage
VIH
0.7*VDD
Max
Unit Notes
Low level input voltage
VIL
High level output voltage
VOH
Low level output voltage
VOL
0.4
V
High level output current
IOH
4
mA
Low level output current
IOL
-4
High level input leakage
IIH
-1
1
µA
Tested at VDD=Vin=3.6V
Low level input current
IIL
-100
-15
µA
Tested at VDD=3.6V and Vin=0V;
‘pull-up’
High level input leakage
IIH
100
15
µA
Tested at VDD=Vin=3.6V; ‘pull-down’
Low level input current
IIL
-1
1
µA
Tested at VDD=3.6V and Vin=0V
V
0.3*VDD
2.5
V
V
mA
Pull-up
Pull-down
Note:
VOH, VOL, IOH and IOL are tested at VDD=3.0V.
IOL is tested at Vout=VOL
IOH is tested at Vout=VOH
Revision 1.0, 19-Jun-07
Page 9 of 136
Data Sheet AS8267 / AS8268
MPIO Inputs with Schmitt Trigger and Selectable Pull-up/Pull-down
Parameter
Symbol
Min
Typ
Max
Unit
Notes
High level input voltage
VIH
0.7 x VDD
Low level input voltage
VIL
0.3 x VDD
V
High level input current
IIH
15
100
µA
Tested at VDD=3.6V and Vin=3.6V;
‘pull-down’
Low level input current
IIL
-100
-15
µA
Tested at VDD=3.6V and Vin=0V;
‘pull-up’
Max
Unit
V
MPIO Outputs with Programmable Drive Strength
Parameter
Symbol
Min
Typ
High level output current
VOH
2.5
V
Tested at VDD=3.0V
Low level output current
VOL
0.4
V
Tested at VDD=3.0V
High level output current
IOH
4
mA
If ‘4mA’ is selected. Tested at
VDD=3.0V and Vout=VOH
Low level output current
IOL
mA
If ‘4mA’ is selected. Tested at
VDD=3.0V and Vout=VOL
High level output current
IOH
mA
If ‘8mA’ is selected. Tested at
VDD=3.0V and Vout=VOH
Low level output current
IOL
mA
If ‘8mA’ is selected. Tested at
VDD=3.0V and Vout=VOL
-4
8
-8
Notes
LCDD Outputs
The Liquid Crystal display driver (LCDD) outputs are specified in the LCD Driver section of this data sheet.
6.4
Electrical System Specification
Parameter
Symbol
Min
Typ
Max
Unit
Notes
Input Signals
Voltage channel input voltage
|VVP|
100
212
mVp
Referenced to VSSA
Current channel input voltage
(Gain=4)
|VI1P|, |VI2P|
150
212
mVp
Referenced to VSSA
Current channel input voltage
(Gain=16)
|VI1P|, |VI2P|
38
54
mVp
Referenced to VSSA
Current channel input voltage
(Gain=20)
|VI1P|, |VI2P|
30
42
mVp
Referenced to VSSA
65
Hz
Mains frequency
fmains
45
Dynamic range current
DR(I)
600:1
Dynamic range power
DR(P)
2000:1
Accuracy
Error variation over dyn. range
Revision 1.0, 19-Jun-07
0.1
err(dr)
0.2
%
Reading
%
1)
Page 10 of 136
Data Sheet AS8267 / AS8268
Parameter
Max
Unit
err(temp)
0.5
%
Within operating
temperature range, 1)
err(cosphi)
0.5
%
From 1 to 0.5, 1)
err(VDD)
0.2
%
1)
J
0.1
%
2)
Vmains
264
V(rms)
240V + 10%, 3)
Measured current
Imax
120
A(rms)
3)
Measurement bandwidth
BW
Error variation over temperature
Error variation over cos(phi)
Error variation with VDD
Output pulse jitter
Mains voltage
Symbol
Min
Typ
1.75
Notes
kHz
Notes:
1) Errors determined during energy measurement using a demo board and a reference meter with high
accuracy (0.05%), which calculates the actual error.
2) Difference between largest and smallest error of 20 successive error samples; maximum meter constant:
1,600i/kWh; reference meter: 10,000 x DUT-meter-constant; measured at 5% Ib, Ib and I max .
3) What is used for system considerations/calculations.
Revision 1.0, 19-Jun-07
Page 11 of 136
Data Sheet AS8267 / AS8268
7. Performance Graphs
0.3
0.3
0.2
0.2
0.1
0.1
Gain 20
Error [%]
Error [%]
Gain 4
0
Gain 16
-0.1
0
Gain 16
-0.1
Gain 4
Gain 20
-0.2
-0.3
0.01
-0.2
0.1
1
10
-0.3
0.01
100
I [A]
Graph 1:
Error as a % of reading for gain setting 4, 16, 20
– Channel l1
Graph 2:
0.3
0.3
0.2
0.2
I [A]
1
10
230V
0
-0.1
Error [%]
290V
100
Error as a % of reading for gain setting 4, 16, 20
– Channel I2
0.1
0.1
Error [%]
0.1
290V
230V
0
170V
-0.1
170V
-0.2
-0.2
-0.3
0.01
Graph 3:
0.1
I [A]
1
10
-0.3
0.01
100
Error as a % of reading with mains voltage
variation – Channel I1
Graph 4:
0,3
0.1
I [A]
1
10
100
Error as a % of reading with mains voltage
variation – Channel I2
0.3
0,2
0.2
3V6
0.1
3V6
3V3
Error [%]
Error [%]
0,1
0
-0,1
3V3
0
-0.1
3V0
3V0
-0,2
-0,3
0,01
Graph 5:
-0.2
0,1
I [A]
1
10
100
Error as a % of reading with variation in VDD –
Channel I1
Revision 1.0, 19-Jun-07
-0.3
0.01
Graph 6:
0.1
I [A]
1
10
100
Error as a % of reading with variation in VDD –
Channel I2
Page 12 of 136
Data Sheet AS8267 / AS8268
0.5
0.5
0.4
0.4
0.3
0.3
0.2
PF=-0.8
0.1
0.1
Error [%]
Error [%]
0.2
0
PF=0.5
0
PF=1.0
-0.1
-0.1
PF=0.5
-0.2
-0.2
PF=-0.8
PF=1.0
-0.3
-0.3
-0.4
-0.4
-0.5
0.01
0.1
Graph 7:
I [A]
1
10
-0.5
0.01
100
Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at -40°C – Channel I1
Graph 8:
I [A]
1
10
100
Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at -40°C – Channel I2
0.5
0.5
0.4
0.4
0.3
0.3
PF=0.5
0.2
0.1
0.2
PF=1.0
Error [%]
Error [%]
0.1
0
-0.1
PF=0.5
PF=1.0
0.1
0
-0.1
PF=-0.8
PF=-0.8
-0.2
-0.2
-0.3
-0.3
-0.4
-0.4
-0.5
0.01
0.1
1
10
-0.5
0.01
100
0.1
1
I [A]
Graph 9:
10
100
I [A]
Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at 25°C – Channel I1
Graph 10: Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at 25°C – Channel I2
0.5
0.5
0.4
0.4
0.3
0.3
PF=0.5
PF=0.5
0.2
0.1
0
0.1
Error [%]
Error [%]
0.2
PF=1.0
-0.1
0
PF=-0.8
-0.1
PF=-0.8
-0.2
-0.2
-0.3
-0.3
-0.4
-0.5
0.01
PF=1.0
-0.4
0.1
1
10
100
I [A]
Graph 11: Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at 85°C – Channel I1
Revision 1.0, 19-Jun-07
-0.5
0.01
0.1
I [A]
1
10
100
Graph 12: Error as a % of reading for PF=1, PF=-0.8, PF=0.5
at 85°C – Channel I2
Page 13 of 136
Data Sheet AS8267 / AS8268
0.3
0.3
0.2
0.2
0.1
Error [%]
Error [%]
0.1
0
-0.1
-0.1
-0.2
-0.2
-0.3
0.01
0.1
I [A]
1
10
-0.3
0.01
100
Graph 13: Error as a % of reading using vconst for mains
voltage value – Channel I1
0.1
1
10
100
I [A]
Graph 14: Error as a % of reading using vconst for mains
voltage value – Channel I2
0.3
0.3
0.2
0.2
0.1
0.1
Error [%]
HP_off
Error [%]
0
0
HP_on
-0.1
HP_on
-0.1
HP_off
0
-0.2
-0.2
-0.3
-0.3
58
60
62
F [Hz]
Graph 15: Error as a % of reading with variation in line
frequency – Channel I1
58
60
62
F [Hz]
Graph 16: Error as a % of reading with variation in line
frequency – Channel I2
Note:
All measurements taken for the compilation of the graphs above were made using a reference meter design
using the application circuit depicted on page 3 of this data sheet and incorporating the AS8267 / AS8268
integrated circuits.
For all graphical measurements, where the temperature was not specified, measurements were made at
ambient (25 °C).
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
8. Detailed Functional Description
The AS8267 / AS8268 integrated circuits have a dedicated measurement front end, which is capable of
measuring active and reactive energy, RMS mains voltage, RMS mains current as well as power factor. There
are two completely separate differential current channel inputs, for measurement of both the Live and Neutral
currents. The two current inputs may be connected to a shunt resistor (I1) and a current transformer (I2). Both
current channels have programmable gains; thus it is possible to connect the shunt resistor to any of the two
differential current inputs. The option to use two current transformers is also available. The AS8267 / AS8268
ICs may be programmed to accept either of the two measured currents for the energy calculation, or may be
programmed to accept the larger of the two currents for the energy calculation.
The AS8267 / AS8268 ICs may also be used for conventional 1-phase single current measurement
applications, where only the Live current is measured. In this case, the I2P and I2N pins are left unconnected
and the second current channel modulator can be powered down.
The voltage channel input for measurement of the line voltage is also differential and is connected to a tap of a
resistive divider of the line voltage. The resistive divider can be set to accommodate any line voltage standard
(V mains ) including 100V, 110V, 220V, 230V or 240V.
A 3.0 to 4.0MHz low power oscillator generates the system clock for the AS8267 / AS8268 ICs. The absolute
clock frequency may be calibrated on-chip. A low power divider is used to generate a 1Hz clock for the on-chip
real time clock/calendar (RTC). The supply voltage to the low power oscillator, the low power divider and the
RTC may be buffered with an external battery in case of mains power drops or failures.
The integrated temperature sensor can be used to compensate for temperature drift of the quartz crystal to
improve measurement accuracy.
The LCD driver (LCDD) signals LSD0 … LSD23 and LBP0 … LBP3 can be directly connected to a liquid crystal
display (LCD), which is used to display the various measured parameters. A total of 80 LCD segments may be
driven by the AS8267 IC and 96 segments may be driven by the AS8268 IC.
A maximum of 12 programmable multi-purpose input/output (MPIO) pins are available for various meter
functions, for example light-emitting diodes (LED) to signal energy consumption, energy direction, fault
condition, etc. These I/O pins may also be programmed for use as bi-directional communication channels such
as an optical interface or an additional Universal Asynchronous Receiver/Transmitter (UART2) Interface,
should it so be required. The AS8267 has 9 x MPIO pins, while the AS8268 has 12 x MPIO pins.
A dedicated Serial Peripheral Interface (SPI) which can be configured as master or slave is also provided.
In master mode an external EEPROM (1kByte up to 32kByte) with a compatible serial peripheral interface can
be connected if required.
In slave mode the interface allows direct access to the internal Flash memory.
The on-chip 8051 compatible microcontroller performs all the required calculations and enables the user to
customize the input and output configuration of the meter. The microcontroller has a 1kB data memory, a
square root calculation facility and a second UART (UART2) for debugging purposes.
The highly reliable 32kByte Flash memory allows storage of program and data. With the integrated security
concept Flash Data can be protected against unauthorised access. The security concept offers password
protection as well as an attack counter which blocks the Flash after five unauthorised attacks.
Revision 1.0, 19-Jun-07
Page 15 of 136
Data Sheet AS8267 / AS8268
A programmable watchdog timer is provided to automatically initiate a system reset when a regular hold-off
signal is not detected by the watchdog timer. The watchdog timer is an optional function which is software
enabled.
A dedicated serial Universal Asynchronous Receiver/Transmitter (UART1) Interface within the System Control
is provided to communicate with the AS8267 / AS8268 ICs and perform all the required programming and
reading of data, especially during the meter production process.
The AS8267 / AS8268 ICs supply voltages (2 x VDDD and VDDA) are typically 3.3 Volts. These supply
voltages should be derived from the V mains with the use of a standard voltage regulated power supply circuit.
An on-chip power supply monitor (PSM) ensures that a reset is generated independently of the supply voltage
rise and fall times. Monitoring of the V mains is provided to ensure early power-down detection. A reset pin
(RES_N) is also available for external system reset. The RES_N pin can be left unconnected if not required.
The individual functional elements of the AS8267 / AS8268 ICs, as well as the relationships between the
various functional blocks are shown in the following block diagram. A detailed description of the AS8267 /
AS8268 ICs system and the flexibility available to the kWh meter designer, through the system programmability
is also described below:
XIN
XOUT
LBP3 ... 0
LSD 23 ... 0
VDD_ BAT
VP
VN
I1P
I1N
I2P
I2N
RXD
TXD
Analog
Front
End
IO 11 ... 0
DSP
UART 1
SC
S_N
MOSI
MISO
Figure 2:
AS8267 / AS8268 block diagram
Revision 1.0, 19-Jun-07
Page 16 of 136
Data Sheet AS8267 / AS8268
8.1
Energy Measurement Front End (Including DSP)
The Energy Measurement Front End is made up of the analog front end and the digital signal processing block
(DSP), which performs the active energy measurement calculations for the microcontroller.
The analog front end comprises of the three Sigma-Delta modulators for the sampling of the mains voltage,
Line current and a second current channel, for the optional measurement of the Neutral current. Also included
in the analog front end is the voltage reference, which provides the temperature stability to the Sigma-Delta
modulators. Setting up for the optimum input conditions for the voltage and current channels is also described
in this section.
The digital signal processing block (DSP) provides the filtering and processing of the output data from the
sigma-delta modulators and ensures that the specified measurement accuracy is provided by the AS8267 /
AS8268. The DSP offers programming of measurement parameters and provides for fast and efficient meter
production calibration procedures.
A power supply monitor (PSM) ensures that a reset is generated independently of the rise and fall times of the
supply voltage (VDD). The PSM is also described in this section.
Analog Front End
The analog front end comprises of three identical Sigma-Delta modulators, which convert the differentially
connected analog voltage and current inputs into digital signals. The two current inputs are gain adjustable to
accommodate both directly connected or galvanically isolated current sensors.
The on-chip voltage reference (VREF) is the most important contributor to the accuracy of the AS8267 /
AS8268 ICs due to it providing temperature stability to the circuit. Considering that the voltage and current
signals are multiplied to derive the energy value, errors introduced prior to multiplication function results in
errors being multiplied. Thus the introduction of errors into the voltage and the current channel inputs will result
in a doubling of the percentage error after multiplication at the energy output.
The temperature coefficient of the VREF is specified at 15 ppm/K typical (30 ppm/K max.).
Current Inputs for Energy Calculation
The AS8267 / AS8268 ICs have 2 identical current inputs, I1P/I1N and I2P/I2N, for measurement of both the
Live and Neutral currents. Either of the two current inputs may be selected for calculating the energy value.
These two differential current inputs are second order Sigma-Delta modulators, with each of the inputs being
provided with selectable gains of 4, 16 and 20. The selectable gains are provided so that the AS8267 / AS8268
ICs may be easily adapted for use with either 2 current transformers or alternatively a shunt resistor and a
current transformer for current sensing. The AS8267 / AS8268 ICs may also be used in a conventional single
current configuration with either a current transformer or shunt resistor being used for current sensing.
The current input signal levels may be programmed by means of on-chip programmable gain settings. The
required gain setting is selected as follows:
Revision 1.0, 19-Jun-07
Page 17 of 136
Data Sheet AS8267 / AS8268
Current Input Gain Settings
Gain
Input Voltage
Comments
Current Inputs I1P, I1N
-30mV≤V I1P ≤30mV
Shunt mode; default setting
16
-38mV≤V I1P ≤38mV
CT mode or shunt mode
4
-150mV≤V I1P ≤150mV
CT mode
20
Current Inputs I2P, I2N
-30mV≤V I2P ≤30mV
20
Shunt mode
16
-38mV≤V I2P ≤38mV
CT mode or shunt mode
4
-150mV≤V I2P ≤150mV
CT mode; default setting
Notes:
1) Refer to the Settings Register (SREG) in the DSP section for programming of the Gain Settings.
For optimum operating conditions, the input signal at the Maximum Current (I max ) condition should be set at
±30mVp, when the Gain = 20, or ±150mVp, when the Gain = 4.
The default Gain, the AS8267 / AS8268 ICs current input gain settings without any programming required, is
Gain = 20 for the I1 input and Gain = 4 for the I2 input.
The value of an ideal shunt resistor, may be calculated as follows:
Assuming an I max rating of 60A (rms) → 84.85A (peak), then a shunt value of 350µΩ would be suitable.
Rshunt =
30mVp
84.85 A p
= 354μΩ
thus a standard 350µΩ shunt resistor may be selected.
The mains currents are sampled at 3.4956kHz, assuming that the recommended crystal oscillator frequency of
3.5795MHz, is used.
The current transformer(s) must be terminated with a voltage setting resistor (R VS ) to ensure the optimum
voltage input level to the current input(s) of the AS8267 / AS8268 ICs. The value of R VS is calculated as
follows:
R VS =
Vin (p )
IL 2
= CT RMS secondary current at rated conditions (V m ains ; I max )
where I L
V in(p) = The peak input voltage to the IC at rated conditions (V mains ; I max ). For example, if Gain = 4,
V in(p) should be set at 150mVpeak.
Example: A current transformer is specified at 60A/24mA and the Gain = 4:
R VS =
Vin (p )
IL
2
=
Revision 1.0, 19-Jun-07
150mV
24mA 2
= 4.42Ω ⇒ 4.3Ω
thus a 4.3Ω Burden resistor may be selected
Page 18 of 136
Data Sheet AS8267 / AS8268
Voltage Input for Energy Calculation
The voltage channel input consisting of inputs VP and VN which are differential, with VP connected to the tap
of a resistor divider circuit of the line voltage and VN connected to VSSA. For optimum operating conditions,
the input signal at VP should be set at 100mVp for the rated voltage condition.
The resistor values for an ideal voltage divider may be calculated as follows:
Assuming a V mains of 230V (rms) → 325V (peak) and R2 = 470Ω (according to the voltage divider shown
below), the value of R1A+R1B may be calculated as follows:
Vmains
R1A+R1B
R2
R1A + R1B = R2 ×
Vin
( Vmains − Vin(P) )
Vin(P)
= 470Ω ×
325 V − 100mV
= 1.53MΩ
100mV
thus R1A = 820kΩ and R1B = 750kΩ resistors may be selected.
The mains voltage is also sampled at 3.4956kHz, assuming that the recommended crystal oscillator frequency
of 3.5795MHz is used.
Digital Signal Processing Block (DSP)
The digital signal processing (DSP) block provides the signal processing required to ensure that the specified
measured accuracy is performed and that the microcontroller (MCU) is provided with the appropriate data and
protocol to perform all the required meter functions. For the description below, please refer to the following
block diagram (Figure 3).
3
The DSP makes allowance for phase correction of the two current channels (i1 and i2) within the Sinc
decimation filters in the phase correction block. The applicable phase correction setting (pcorr_i1 or pcorr_i2)
is selected (sel_i), depending upon which current (i1 or i2) is being used for the power calculation.
The equalization filters on the voltage and current channels which may be by-passed (sel_equ), correct for the
attenuation introduced by the decimation filters at the edge of the input frequency band, while the high pass
filters, which may also be by-passed (sel_hp), eliminate any DC offsets introduced into the input channels.
Independent calibration of the voltage (cal_v) and current signals (cal_i1 and cal_i2) is done after the voltage
and current signals are provided for power calculation. This ensures that calibration of the voltage (sos_v),
current channel 1 (sos_i1), current channel 2 (sos_i2) has no influence on the power (np) calibration.
Revision 1.0, 19-Jun-07
Page 19 of 136
Data Sheet AS8267 / AS8268
The iMux (current multiplexer) allows the selection of the applicable current for power calculation (sel_i), while
the vMux (voltage multiplexer) allows the selection of either the mains voltage data, or a constant voltage
value, vconst (sel_v). The multiplication of the appropriately selected voltage and current signals is then
performed.
After multiplication, the next multiplexer (sel_p) enables the selection of either instantaneous power or real
power, which is derived through low pass filtering, PLP. The direction indicator output (diro) is derived from the
output of the power low pass filter (PLP).
The following multiplexer (creep) allows the selection of the power signal, or blocks the power signal,
depending on the required anti-creep and starting current thresholds, which may be set in the microcontroller.
Only when constant voltage value (vconst) is selected by the vMux (voltage multiplexer) or when diro=1, it is
necessary to derive the absolute power value, for measurement (Abs).
The first pulse generator (Fast Pulse Gen) produces fast internal pulses, with the number of pulses being
proportional to the measured energy. The multiplexer enables the selection of the appropriate pulse level
(pulselev_i1 or pulselev_i2) depending on the current being used for energy measurement (sel_i). The output
of the Fast Pulse Gen is always directly proportional to the LED pulse output, generated in the LED Pulse Gen.
The LED output pulse rate is selectable (mconst). The polarity of the LED output pulses is also selectable
(ledpol).
To ensure that the power data transferred to the microcontroller (MCU) is identical to that of the LED pulses,
the power accumulator (P_ACCU) counts the pulses generated by the Fast Pulse Gen. After a defined number
of sampling periods (nsamp), an interrupt is sent to the MCU, for the MCU to collect the accumulated energy
data.
Revision 1.0, 19-Jun-07
Page 20 of 136
Data Sheet AS8267 / AS8268
pddeton
i1
i2
Equ
Filter
ADC
Phase Correction
v
ADC
ADC
HP
Filter
X
Registers
PD_DET
alarm
Square
Accu
sos_v
Square
Accu
sos_i1
Square
Accu
sos_i2
cal_v
Equ
Filter
HP
Filter
Equ
Filter
HP
Filter
sel_equ
sel_hp
X
cal_i1
X
cal_i2
Mux
vconst
sel_i
sel_i
iMux
vMux
pcorr_i1
pcorr_i2
sel_v
X
PLP
<0?
sel_p
diro
Mux
"0"
creep
Mux
sel_v
Abs
nsamp
pulselev_i1
pulselev_i2
Mux
sel_i
Fast
Pulse
Gen
P_ACCU
LED
Pulse
Gen
np
LED
mconst
ledpol
Figure 3:
AFE block diagram
Revision 1.0, 19-Jun-07
Page 21 of 136
Data Sheet AS8267 / AS8268
Phase Correction
3
The DSP provides phase correction of the two current channels (i1 and i2) by means of the Sinc decimation
filters in the phase correction block. Only one of the phase correction settings (pcorr_i1 or pcorr_i2) is valid at
a time, depending on which current (i1 or i2) has been selected for the power calculation (sel_i).
The phase correction step size is dependent upon the main oscillator frequency selected (f osc ) and the mains
frequency (f mains ). Assuming a 3.579545MHz crystal oscillator frequency and 50Hz mains frequency, the phase
can be corrected in steps of 2.41’ or 0.04 degrees.
pcorr
Phase Correction
[unit(s)]
Bit 8
0
0
Bit 7
1
1
Bit 6
1
1
Bit 5
1
1
Bit 4
1
1
Bit 3
1
1
Bit 2
1
1
Bit 1
1
1
Bit 0
1
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
255
254
…
127
126
…
2
1
0
-1
-2
…
-127
-128
…
-255
-256
One ‘unit’ equals a certain phase shift related to the mains frequency:
1 unit = 360° ×
fmains
fosc / 8
Phase Correction [°] = # units × 360° ×
fmains
fosc / 8
where fmains is the mains frequency and fOSC is
the oscillator frequency.
Example:
1 unit = 360° ×
fmains
= 0.04023 ° = 2.41°
fosc / 8
255 units = 255 x 0.04023° = 10.26°
Revision 1.0, 19-Jun-07
Page 22 of 136
Data Sheet AS8267 / AS8268
Calculating Phase Correction Factors
The measured phase_error in percentage is defined by the following formula
phase _ error =
cos( 60° + phase _ shift ) − cos( 60°)
× 100
cos( 60°)
[%]
while the phase_shift in degrees, is calculated as follows:
⎡⎛
⎤
phase _ error [%] ⎞
phase _ shift = arccos ⎢⎜1 +
⎟ × cos( 60°)⎥ − 60°
100
⎠
⎣⎝
⎦
phase_correction= – phase_shift
The required phase correction factor can be determined from error measurements with a power factor (PF) less
than 1.
Assuming that at PF = 1 the meter has been calibrated and the error is approximately 0 for I cal (calibration
current), the PF is reduced and the effect of phase differences results in an increased error (‘phase_error’).
Example: The phase_error at PF = 0.5 (ϕ = 60°) is measured to be 9.2 %.
The related phase shift can be calculated using the following formula:
⎛ ⎛ phase _ error [%] ⎞
⎞
phase _ shift = arc cos⎜⎜ ⎜1 +
⎟ × cos 60° ⎟⎟ − 60°
100
⎠
⎝⎝
⎠
where the phase_error is the measured error in percentage and cosΦ is the phase angle.
For phase_error = 9.2[%] the phase_shift is -3.0° and therefore the phase correction is 3.0°.
If f osc = 3.579545MHz and f mains = 50Hz, one phase correction unit represents 2.41’, which is 0.04023°.
Thus the phase correction factor must be set to
3 .0 °
= 74.57 units
0.04023 °
= 75 units.
The pcorr register has to be set to 4Bh.
Equalization Filters
The equalization filters in the voltage and current channels correct for the attenuation effects introduced by the
decimation filters around the frequency band limit. The resulting transfer curve after the equalization filter has
approximately 0dB attenuation over the entire frequency band.
The equalization filters may be by-passed (sel_equ), if required.
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Data Sheet AS8267 / AS8268
High-Pass Filters
The high pass filters in the voltage and current channels, with corner frequencies of <10Hz, correct for DC
offsets introduced into the input channels.
Each of the voltage and current channels has a separate high pass filter in order to avoid any phase shift being
introduced between the voltage and the two current channels.
The high pass filters may also be by-passed (sel_hp), if so desired.
Corner frequency:
<10Hz
RMS Calculations
The DSP provides the voltage and current channel data in ‘sum-of-squares’ format. To calculate RMS values
from the voltage (sos_v) and current (sos_i1 and sos_i2), the following formula should be applied for the
voltage and current respectively:
Vrms =
Irms =
1 nsamp 2
∑ Vi ,
nsamp i=1
1 nsamp 2
∑ Ii ,
nsamp i=1
nsamp
where
∑
i=1
nsamp
where
∑
i=1
Vi 2 is the sos_v value
Ii 2 is the sos_i value
nsamp should be selected in order to achieve coherent sampling as close as possible:
e.g. f s = 3.4956kHz (f osc = 3.579545MHz) ⇒ nsamp = 3496 should be selected if the MCU has to be
interrupted every 1 second.
Refer to Squareroot Block (SQRT) for a detailed description of the programming sequence of the squareroot
input operand.
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Data Sheet AS8267 / AS8268
Calibration of V and I Channels
The single channel data may be corrected with a 16-bit calibration value.
-5
The calibration range is [1 LSB; 2 – 1 LSB], step size (1 LSB): 3.052 x 10 .
Calibration Register Setting
Value
0000h
0
0001h
0.00003052 (= 1 LSB)
…
…
2000h
0.25
…
…
4000h
0.5
…
…
8000h
1.0
…
…
FFFFh
1.99996948 (2 – 1LSB)
The V and I channel RMS calculation and calibration is described below (V and I channel are identical, thus
only the I channel is shown):
The ideal values after RMS calculations of voltage and current are:
RMS_V(ideal) = 479(rms)
RMS_I(ideal) = 292,110(rms)
These values assume ideal input conditions with V in = 100mVp at rated conditions and I in = 30mVp (Gain = 20)
at rated conditions.
Due to non-ideal components a different RMS value is calculated: RMS_I(actual). From this, the required
calibration factor is calculated using the following formula:
cal _ i =
RMS _ I(ideal)
RMS _ I(actual)
The following formula calculates the actual value to be programmed into the calibration registers (cal_v; cal_i1;
cal_i2):
cal _ i(reg) = hex(round(cal _ i × 32,768 ))
e.g.
RMS_I(ideal) = 292,110 at 40A
Ical = 10A → RMS_I (ideal) =
292,110
4
= 73,027 at 10A
Iactual = 9.2A → RMS_I (actual) = 67,185
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Data Sheet AS8267 / AS8268
⎛
⎞⎞
⎛ 73,027
cal _ i1(reg) = hex⎜⎜ round ⎜⎜
× 32,768 ⎟⎟ ⎟⎟
67
,
185
⎠⎠
⎝
⎝
= hex (round (35,617.31))
= hex(35,617)
= 8B21h
Constant Voltage Register (vconst)
The vconst registers (9334h and 9335h) provide a predefined voltage value that can be used for calculating
energy when the V mains is not available.
The default value of vconst is 2877 (0B3Dh) which translates into an equivalent V mains value of 311V.
The energy is calculated using vconst and the selected current (i1 or i2) when sel_v in the SREG/Select
register is set to ‘1’.
The vconst value may be calculated according to the formula:
vconst = RMS _ V × 2 × π
Example: RMS_V = 479
⇒ vconst = 479 × 2 × π
(Once the voltage channel has been calibrated, 479
is the typical value when V mains = 230V)
= 2,128
Note: When vconst is used for the calculation of energy, sel_p must be set to ‘0’.
Low Pass Filter for Real Power (PLP)
When the instantaneous power is low pass filtered the result is practically a DC value for the power, which is
termed real power. It is generally preferred to use real power to generate pulses for the calibration, as the
duration between pulses is more constant (pulse jitter).
Corner frequency:
18.6Hz
The low pass filter ensures that the power output pulse jitter is minimised.
Direction Indicator (DIRO)
The direction indicator (DIRO) situated in the Status Register (Bit 4) defines the direction of the measured
power. The direction is determined by the phase relationship between the Mains voltage and selected Mains
current (i1 or i2).
When bit 4 in the Status Register is ‘0’, the Mains voltage and selected Mains current are in phase, thus
indicating positive energy flow. When bit 4 in the Status Register is ‘1’, the Mains voltage and the selected
Mains current have a phase reversal, indicating negative energy flow. The energy calculation (np) is generated
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Data Sheet AS8267 / AS8268
from positive energy, thus when DIRO = 1, the negative energy is converted to positive energy by the ‘Abs’
block shown in Figure 3:
AFE block diagram.
Should the meter application require unidirectional energy measurement, the MCU can separately derive both
the positive and negative energy values, depending on the status of the DIRO bit.
Accumulator for Real Power (P_ACCU)
To ensure that the power information transferred to the MCU is identical to that of the LED pulses, the P_ACCU
counts the pulses generated by Fast Pulse Gen. After ‘nsamp’ (nyquist) sampling periods an interrupt is sent to
the MCU requesting to fetch the new energy information. (Interrupt line ‘IE.0’ goes high and the ‘data available
interrupt’ (dai) flag in the SREG/Status register is set). The ‘ack’ bit in the SREG/Status register is also set to
1. If the MCU takes the energy information, it has to reset the ‘ack’ bit signalling that the energy information
has been taken. If the ‘ack’ bit is not reset the P_ACCU will add the ‘old’ energy information to the ‘new’ energy
information accumulated in the following cycle.
In any event, the MCU must reset the dai flag in order to clear the interrupt.
Wait for
fast pulse
New fast
pulse?
Y
Increment
P_ACCU
N
nsamp
reached?
Y
np = P_ACCU + np (old)
P_ACCU = 0
N
IE.0 = 1
dai = 1
ack = 1
N
ack = 0?
Y
Y
np = 0
Note: The above flow chart assumes that the dai flag is always reset in time before the next interrupt is
generated.
Pulse Generation
Two pulse generators are provided to ensure that virtually any LED pulse rate output can be programmed for
display and calibration purposes. The first pulse generator (Fast Pulse Gen) produces fast internal pulses.
These fast pulses are accumulated in the power accumulator (P_ACCU) for energy data transfer to the MCU.
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Data Sheet AS8267 / AS8268
The second pulse generator (LED Pulse Gen) produces the LED output pulses (meter constant) from the fast
internal pulses. This type of data interface ensures that the MCU receives exactly the same energy information
as is displayed by the LED pulses.
In case of ‘creep’, the power samples to be added will be set to 0.
The following flow chart shows the basic flow diagram for pulse generation:
Wait for next
power samples
Add power
sample to accu
Accu>
threshold
defined by
pulse_lev?
Y
Generate pulse
N
The Fast Pulse Gen output pulse rate always has the same relationship with the LED pulse rate defined by
mconst. Only if LED is calibrated to a meter constant different from those provided in the mconst table, will the
fast internal pulse rate be different.
Formula for fast internal pulse rate (PR int ):
PRint = 204,800 ×
1i =
T arg et Pulse Rate
[i / kWh ]
mconst
1,000 × 3,600
[Ws ]
PRint
where mconst is the meter constant.
when 1i is one impulse representing an energy equivalent.
e.g.
TargetPulseRate = mconst = 3200i/kWh
PR int = 204,800 × 1 [i/kWh]
1i =
1,000 × 3,600
= 17.58 [Ws ]
204,800
Active Power Calibration (Pulse_lev)
This paragraph describes how the active power measurement within the AS8267 / AS8268 ICs is calibrated.
The parameter Pulse_lev is the main parameter which determines the output frequency of the Fast Pulse Gen.
This frequency relates to the measured power and is the basis from which the output pulse rate is derived.
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Data Sheet AS8267 / AS8268
Prior to system calibration, the appropriate value for the parameter Pulse_lev must be calculated to produce
the required output pulse rate. The calibration exercise must accommodate all non-idealities that are present in
the meter system.
The Pulse_lev is specified such that a typical pulse rate of 204,800i/kWh can be achieved.
During energy pulse calibration the correct Pulse_lev is determined in order to get the desired pulse rate.
The default value for Pulse_lev is defined for I max =40A and V mains =230V.
Default Pulse_lev: 570,950 (Pulse_lev(default))
Example for Pulse_lev calculations:
Pulse _ lev(ideal) =
230 V 40 A
×
× Pulse _ lev( default )
Vmains Imax
V mains (V)
I max (A)
Pulse_lev (ideal)
230
100
228,380
230
80
285,475
230
60
380,633
230
40
570,950
230
20
1,141,900
230
10
2,283,800
240
100
218,864
240
80
273,580
240
60
364,774
240
40
547,160
240
20
1,094,321
240
10
2,188,642
Notes
Default setting
Pulse_lev(ideal) = 230/V mains x 40/I max x 570,950
Comparison Calibration Method
The most common calibration method is the comparison of energy reading of the meter under test (MUT)
against a standard or reference meter. Normally, the standard, or reference meter has a considerably higher
pulse rate than the meter under calibration. Reference meter output pulses are then counted between
consecutive led pulses. To facilitate the calibration procedure, a pulse counter is provided in the MPIO block.
In this case, the absolute calibration time and the calibration current are not relevant for the calibration cycle.
The basic calibration setup is shown below:
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Data Sheet AS8267 / AS8268
MUT
Reference
Meter
Pulse Counter
PC
IO1
led
I
Figure 4:
Basic setup for comparison calibration method (using IO1 as example input)
Note: An I/O used as push-button input can be used for the input of the reference meter pulses during
calibration.
The standard or reference meter pulses are counted between two pulses from the meter to be calibrated.
Ideally the sum of the pulses would exactly be the ratio between standard meter or reference pulse rate and
the pulse rate of the meter under test. From the deviation the corrected Pulse_lev may be calculated.
Pulse _ lev(corrected) = Pulse _ lev(ideal) ×
Ni
,
Na
where Ni is the ideal number of pulses
and Na is the actual number of pulses
(PCNT register in MPIO).
The actual number of pulses is available
in the pulse count register (PCNT).
The ideal number of pulses Ni is the ratio between the pulse rates of the reference meter and the meter under
test, which is always >1. The formula for Ni is as follows:
Ni =
PR(ref )
,
LED Pulse Rate(mconst )
where PR(ref) is the reference meter constant.
The Pulse_lev (ideal) is calculated using the following formula:
Pulse _ lev(ideal) =
230 V 40 A
×
× Pulse _ lev( default )
Vmains Imax
Example
The reference meter has a pulse rate, which is 10,000 times greater than the pulse rate of the AS8267 /
AS8268 LED output.
LED Pulse Rate
PR(ref)
= 3,200i/kWh
= 3,200 x 10,000
⇒ Ni = 10,000
During a calibration cycle we measure 11,000 pulses between two LED pulses.
⇒ Na = 11,000
Assuming a meter with V mains = 230V
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I max = 60A
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Data Sheet AS8267 / AS8268
Pulse _ lev (ideal) =
230 V 40 A
×
× 570,950
230 V 60 A
= 380,633
Pulse _ lev (corrected) = 380,633 ×
10,000
= 346,030
11,000
LED Meter Constant Selection (mconst, 9330h)
The LED pulses are derived directly from the fast internal pulses (204,800i/kWh).
The ‘mconst’ register in SREG specifies the LED pulse rate:
MSB
LSB
-
-
-
Bit
7
Symbol
-
Function
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
mconst[3]
2
1
0
mconst[2]
mconst[1]
mconst[0]
-
mconst[3]
mconst[2]
mconst[1]
mconst[0]
Bit3
Bit2
Bit1
Bit0
LED Pulse Rate
0
0
0
0
204,800
0
0
0
1
102,400
0
0
1
0
51,200
0
0
1
1
25,600
0
1
0
0
12,800
0
1
0
1
6,400
0
1
1
0
3,200
0
1
1
1
1,600
1
0
0
0
800
1
0
0
1
400
1
0
1
0
200
1
0
1
1
100
1
1
X
X
100
If the target meter constant is different from one of the selectable (mconst) meter constants defined above:
e.g. 1,000i/kWh (Target Pulse Rate)
The same formula Ni =
Revision 1.0, 19-Jun-07
PR(ref )
can be used, but Ni is calculated using the Target Pulse Rate:
LED Pulse Rate(mconst )
Page 31 of 136
Data Sheet AS8267 / AS8268
Ni =
PR(ref )
T arg et Pulse Rate
(Important: Select a pulse rate which is close to mconst, for the Target Pulse Rate, so that the Pulse_lev stays
within reasonable limits.)
After this calibration the energy equivalent of 1 fast pulse (1i) is different!
Standard: internal pulse rate: 204,800i/klWh
⇒ 1i =
1,000 × 3,600[Ws ]
= 17.58 Ws
204,800
When a special pulse rate is required, the following formula applies:
⇒ 1i =
1,000 × 3,600
LED PulseRate
×
[Ws ]
204,800
T arg etPulseRate
Example:
Assuming a pulse rate of 1,000 is required:
1,600 → 204,800
1,000 → 204,800 x 1,000/1,600
⇒ 1i =
1,000 × 3,600[Ws ]
= 28.13 Ws
204,800 × 1,000 / 1,600
Mains Current Leads/Lags Mains Voltage
The i_lead flag in the SREG/Status register determines if the mains current leads the mains voltage or lags the
mains voltage. The data is provided for reactive power calculation, to establish if the measured power is
capacitive or inductive.
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Data Sheet AS8267 / AS8268
LED Output Timing
The pulses on the LED output indicate the amount of energy that has been consumed over a certain period of
time. Each pulse has an equivalent that can be set in the SREG/mconst register exactly. The unit is impulses
per kWh (i/kWh).
This output may be used for calibration.
The polarity of the LED pulses may be selected via the ledpol bit in the SREG/Select Register for either
positive or negative going pulses.
Timing Diagram
Timing Parameters
Parameter
Pulse width
Symbol
t1
Min
Typ
80
Max
Unit
ms
Notes
50% duty cycle is enabled when the LED
period is less than 160ms. For mconst=0,
t1 will be 17.9µs.
Register Interface to MCU
One register block contains the data for the Meter Data Register (MDR) and the Settings Register (SREG),
hence only one interface to the MCU is required.
Meter Data Register (MDR)
The meter data register is updated after ‘nsamp’ samples. Then an interrupt is issued to the MCU, which may
take the energy data and process them further on. When an interrupt is generated the ‘ack’ bit in the
SREG/Status register is set. If the MCU takes the data, it has to reset the ‘ack’ bit.
If the ‘ack’ bit has not been reset by the MCU when a new set of data is ready, the previous np value will be
added to the new one.
In any case the dai flag in the SREG/Status register must be reset in order to clear the interrupt.
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Data Sheet AS8267 / AS8268
The following table shows the data which is available in the MDR:
Register Name
Address
Reset Value
samptoend[7:0]
9300h
FFh
samptoend[15:8]
9301h
FFh
np[7:0]
9302h
00h
np[15:8]
9303h
00h
np[23:16]
9304h
00h
np[31:24]
9305h
00h
sos_v[7:0]
9306h
00h
sos_v[15:8]
9307h
00h
sos_v[23:16]
9308h
00h
sos_v[31:24]
9309h
00h
sos_v[35:32]
930Ah
00h
sos_i1[7:0]
930Bh
00h
sos_i1[15:8]
930Ch
00h
sos_i1[23:16]
930Dh
00h
sos_i1[31:24]
930Eh
00h
sos_i1[39:32]
930Fh
00h
sos_i1[47:40]
9310h
00h
sos_i1[53:48]
9311h
00h
sos_i2[7:0]
9312h
00h
sos_i2[15:8]
9313h
00h
sos_i2[23:16]
9314h
00h
sos_i2[31:24]
9315h
00h
sos_i2[39:32]
9316h
00h
sos_i2[47:40]
9317h
00h
sos_i2[53:48]
9318h
00h
Description
Indicates how many samples are left (until nsamp), before the next
interrupt is generated. Using this information the MCU can
determine if it still has time to transfer the MDR data to the MCU
memory.
number of fast pulses, equivalent to energy information
accumulated during nsamp samples
sum of squares of voltage channel samples
sum of squares of current channel 1 samples
sum of squares of current channel 2 samples
Notes:
1) MDR is read-only for MCU. (except for ‘MCU debug mode’, then you can set the register values as
described.)
2) Unused addresses will simply be ignored.
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Data Sheet AS8267 / AS8268
The following flowchart describes how accumulators and registers work together:
Accumulate fast
pulses (np);
accumulate
squares (sos)
ack reset by
MCU?
Y
Reset np-register
(MDR)
N
nsamp reached?
Y
Transfer sosaccus to registers
(MDR/sos)
N
Add P_ACCU to
np-register
Clear sos accus
and P_ACCU
Calculation of Apparent Power
S[VA ] = Vrms × Irms =
=
1 nsamp 2
1 nsamp
× Ii ×
∑
∑ × Vi2
nsamp i=1
nsamp i=1
1
1
× sos _ v ×
× sos _ i
nsamp
nsamp
Calculation of Real Power
P[W ] = np × 1i,fast pulse rate
1i,fast pulse rate =
1,000 × 3,600
[Ws ]
204,800
Calculation of Reactive Power
Q[VAr ] = S 2 − P 2
Calculation of cos( ϕ )
cos(ϕ) =
P
S
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Data Sheet AS8267 / AS8268
Settings Register (SREG)
The settings register contains data stored by the MCU, which are used, for example, for calibration purposes, but also for
general settings like input gain.
Register Name
Address
Reset Value
Description
pcorr_i1[7:0]
9320h
00h
pcorr_i1[8]
9321h
00h
pcorr_i2[7:0]
9322h
00h
pcorr_i2[8]
9323h
00h
cal_v[7:0]
9324h
00h
cal_v[15:8]
9325h
80h
cal_i1[7:0]
9326h
00h
cal_i1[15:8]
9327h
80h
cal_i2[7:0]
9328h
00h
cal_i2[15:8]
9329h
80h
pulselev_i1[7:0]
932Ah
46h
pulselev_i1[15:8]
932Bh
B6h
pulselev_i1[23:16]
932Ch
08h
pulselev_i2[7:0]
932Dh
46h
pulselev_i2[15:8]
932Eh
B6h
pulselev_i2[23:16]
932Fh
08h
mconst[3:0]
9330h
06h
-
9331h
-
nsamp[7:0]
9332h
ACh
nsamp[15:8]
9333h
0Dh
vconst[7:0]
9334h
3Dh
vconst[13:8]
9335h
0Bh
A predefined voltage value which may be used for energy
calculation in the event of Vmains not being available.
Select
9336h
80h
Select register
Gains
9337h
03h
Gain settings register
Status
9338h
00h
Status register
Sets the phase correction for current channel i1.
Sets the phase correction for current channel i2.
Calibration factor for voltage channel. Only acts on sos_v data.
Calibration factor for current channel i1. Only acts on sos_i1
data.
Calibration factor for current channel i2. Only acts on sos_i2
data.
Pulse_lev for fast pulse generation if current channel i1 is
selected (sel_i).
Pulse_lev for fast pulse generation if current channel i2 is
selected (sel_i).
Meter constant for LED pulse generation
Not used
Sets number of samples before next update of MDR.
Note: Unused addresses will simply be ignored. Unspecified bits will also be ignored.
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Data Sheet AS8267 / AS8268
Select Register (Select, 9336h)
MSB
LSB
ledpol
Bit
-
-
sel_p
sel_i
sel_v
sel_hp
sel_equ
Symbol Function
7
ledpol
6
-
Selects polarity of LED pulses:
0: negative going pulses
Not used
5
-
Not used
4
sel_p
3
sel_i
2
sel_v
1
sel_hp
0
sel_equ
1: positive going pulses (default)
Select between instantaneous and real power for pulse generation
0: instantaneous power
1: real power (low-pass filtered instantaneous power)
Select current channel for power calculation (Fast Pulse Gen)
0: i1
1: i2
Select voltage channel data
0: selects voltage channel analog input
1: selects the predefined constant ‘vconst’
Select high-pass filter
0: high-pass
Select equalisation filter
0: equalizer
1: no high-pass
1: no equalizer
Gain Settings Register (Gains, 9337h)
MSB
LSB
-
Bit
-
-
-
gain_i2[0]
gain_i1[1]
gain_i1[0]
Bit1
0
0
1
1
Bit0
0
1
0
1
Gain
4
16
16
20
Bit1
Bit0
Gain
0
0
1
1
0
1
0
1
4
16
16
20
Symbol Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
gain_i2[1]
Gain setting for current channel 2 modulator
2
gain_i2[0]
1
gain_i1[1]
Gain setting for current channel 1 modulator
0
gain_i2[1]
gain_i1[0]
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Data Sheet AS8267 / AS8268
Status Register (Status, 9338h)
MSB
LSB
creep
Bit
mdm
i_lead
diro
pddeton
alarm
dai
ack
Symbol Function
7
creep
6
mdm
Indicator for creep situation, used as disable signal for LED pulse generation
0: no creep
1: creep
MCU Debug Mode flag
Enables the MDR to be written by the MCU. This is useful for debugging when the
programmer wants to know exactly what is received from the DSP block.
0: normal mode
5
i_lead
4
diro
1: debug mode as described later in the data sheet.
Indicates if the mains current leads or lags the mains voltage.
0: mains current lags (inductive)
1: mains current leads (capacitive)
DIRO indicator, signals when voltage and current are out of phase by 180°
0: 0° phase difference
1: 180° phase difference
Can only be read by MCU.
3
2
pddeton
alarm
Enables the power-down detector functionality
0: no PD_DET functionality
Indicates when the Vmains is falling below a predefined threshold. If this happens an interrupt is
generated and the alarm flag is set. The interrupt will be reset only when the alarm flag is reset.
0: no alarm
1
dai
1: PD_DET on
1: alarm that Vmains is low
Data Available Interrupt flag
Indicates that an interrupt has been generated because new meter data are available.
0: no interrupt
1: interrupt due to new data
Set only by DSP. Resetable only by software (MCU).
A clear of ‘dai’ means that the irq is set back to 0.
0
ack
Acknowledge bit, indicates if MCU has transferred newly available data to its memory
1: Set by DSP, when data are ready on MDR. (not settable by MCU!)
0: Reset by MCU, when data have been taken.
When ack gets reset the contents of MDR-np is set to zero. The ‘P_ACCU’ always adds the contents of
MDR-np to the last value just before it transfers new data to the MDR. Thus, if ack=0 the MDR-np is
reset and nothing is added to the P_ACCU. If ack has not been cleared the np data is still available and
is added to the P_ACCU.
Current Channel Comparison
The two current channels can be compared by the microcontroller (MCU), if the greater of the two currents is
required for energy calculation. This is done by comparing the calculated RMS values of the two currents. The
threshold for changing from I1 to I2 (or visa versa) can also be set in the MCU software.
Creep Detection
The standards specify that no pulses must be generated when there is no current flow (‘creep’). Additionally
there is a threshold for current when the meter must generate pulses in any case (‘starting current’). Therefore
a detection circuit must guarantee that these two situations are under control.
The AS8267 / AS8268 current channel data are evaluated in the MCU to find out if there is a ‘creep’ situation.
The related signal is used to stop the pulse generation if required.
Revision 1.0, 19-Jun-07
Page 38 of 136
Data Sheet AS8267 / AS8268
MCU Debug Mode
When mdm flag of SREG/Status register is set, the DSP block enters the MCU debug mode. Here the MDR can
be written through the MCU interface. In this mode the DSP block is not allowed to write to the MDR.
Special functionality:
1) ack set to 0 → np is set to 0 (i.e. must be set again by MCU)
2) when ack is not reset by the MCU the np value is doubled, i.e. a shift left is done.
Note: Also in debug mode an interrupt is generated after nsamp samples.
Power Supply Monitor (PSM)
The AS8267 / AS8268 ICs have an on-chip power supply monitor (PSM) that ensures a reset is generated
independently of the supply voltage (VDD) rise and fall times.
A built in hysteresis is provided to accommodate slow changes on the VDD, to ensure clean signal switching.
Parameter
Symbol
Min
Threshold positive edge
Vth,pos
Threshold negative edge
Hysteresis
Table 1:
Typ
Max
Unit
2.6
2.9
V
Vth,neg
2.2
2.8
V
Hyst
100
Notes
mV
Power supply monitor: Power-on reset specifications
To ensure sufficient time is available to store the meter data in an EEPROM during power-down, it is necessary
to detect the falling supply voltage as fast as possible. Should only the VDD be monitored, an external
capacitor in the 3.3V power supply could sustain the VDD supply voltage even after the V mains has begun to fall.
For this reason, the AS8267 / AS8268 ICs allow the monitoring of the V mains to ensure early power-down
detection. The power-down detector function (PD_DET) is enabled in the SREG/Status register.
An alarm signal is generated, when the V mains falls below a specified mains voltage threshold, which enables
the MCU to react with sufficient time. It is also possible to calculate energy during power-down detection,
taking a constant voltage value for calculation of the energy value.
The mains voltage threshold is calculated as follows:
Vmains (alarm) =
=
Vmains × 512
RMS _ V(ideal) × 2
230 × 512
479 × 2
= 173.8 VAC
External System Reset (RES_N)
An external reset pin (RES_N) is provided for system reset. RES_N is active LOW (i.e. logic ‘0’ will initiate a
system reset). A system reset via the RES_N pin is OR-ed with the main system power-on reset generated by
the power supply monitor PSM.
RES_N is internally pulled high.
Revision 1.0, 19-Jun-07
Page 39 of 136
Data Sheet AS8267 / AS8268
System Timing and Real Time Clock (RTC)
A low power crystal oscillator using a 3.0 to 4.0MHz crystal provides the AS8267 / AS8268 system timing. The
low power oscillator is internally connected to a low power divider, which provides a 1Hz signal to the real time
clock, which may be trimmed. The RTC circuit may be battery powered to continue operating even when V mains
is interrupted.
VDD_BAT
div[19:0]
XIN
XOUT
Low Power
Oscillator
Low Power
Divider
RTC
MCU
clk_1hz
Mclk
Figure 5:
Register
Interface
1Hz
System timing and RTC block diagram
Low Power Oscillator (LP_OSC)
The low power oscillator is connected to an external 3.0 to 4.0MHz crystal. The oscillator can be operated in
normal mode or low power mode.
Should a suitable external clock signal be preferred, this may be directly connected to the XIN pin, which is fed
through to output ‘Mclk’. In this case, XOUT is left unconnected.
Parameter
Symbol
Min
Typ
Max
Unit
Notes
Current consumption, normal mode
Iosc,norm
20
µA
VDD supply
Current consumption, low power mode
Iosc,bat
7
µA
VDD_BAT = 2VDC @
25°C
Frequency range
Supply voltage range
Duty cycle
fosc
3.0
3.579545
4.0
MHz
VDD_BAT
2.0
3.3
3.6
V
duty_cyc
45
55
%
Low Power Divider (LP_DIV, 9130h – 9132h)
The main oscillator output frequency (Mclk) is divided down to 1Hz for the real time clock (RTC). The option to
use alternative crystal frequencies and still derive a 1Hz clock signal for the real time clock (RTC), is provided
through this internally programmable divider.
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Data Sheet AS8267 / AS8268
For power-saving reasons, the fast oscillator clock is first divided down by a fixed ratio (divide by 5) and then
the programmable divider follows.
Mclk
div5
clk_1hz
programmable divider
div[19:0]
Parameter
Input frequency range
Division factor
Symbol
Min
Typ
Max
Unit
fMclk
3.0
3.579545
4.0
MHz
n
1,048,575
Notes
1)
The setting of div[19:0] is located in the RTC registers (addresses: 9132h – 9130h)
Note:
1) The division factor n is effective on the frequency Mclk/5. It represents the actual division factor minus 1.
Example: Calculate n for oscillator frequency 3,579,545Hz. The frequency after the div5 is 715,909Hz.
Therefore, n must be 715,909 – 1 = 715,908 to get 1Hz.
2) Setting n = 1 means a division factor of 2.
Real-Time Clock (RTC)
The RTC can be directly accessed from the MCU via a dedicated interface register.
Two alarm registers are provided to indicate a certain time instance, such as the start of a new month. In that
case an interrupt is sent to the MCU. Constant frequency deviations of the crystal that is used can be trimmed
to an accuracy of better than +/-1.4ppm.
A seconds counter is provided which may be used for certain meter calculations. There is only one interrupt
output. The source of the interrupt is indicated in the Control/Status 2 register.
RTC
Register Interface
Time/
Calendar
Registers
MCU
Alarm
Registers
Seconds
Counter
Frequency
Trim
LP_DIV
Revision 1.0, 19-Jun-07
LP_DIV
Setting
Page 41 of 136
Data Sheet AS8267 / AS8268
RTC Registers
Register Name
Address
Reset Value
Notes
Seconds / VL
9100h
80h
Minutes
9101h
00h
Hours
9102h
00h
Days
9103h
01h
Day of the Week
9104h
00h
Month / Century
9105h
01h
Years
9106h
00h
Control / Status 1
9110h
10h
Control / Status 2
9111h
00h
Seconds Timer Byte 0
9112h
01h
Seconds Timer Byte 1
9113h
00h
Minute Alarm 1
9114h
00h
Hour Alarm 1
9115h
00h
Day Alarm 1
9116h
01h
Month Alarm 1
9117h
01h
Years Alarm 1
9118h
00h
Minute Alarm 2
9119h
00h
Hour Alarm 2
911Ah
00h
Day Alarm 2
911Bh
01h
Month Alarm 2
911Ch
01h
Years Alarm 2
911Dh
00h
Divider Register Byte 0
9130h
84h
[7:0] = div [7:0] (LP_DIV)
Divider Register Byte 1
9131h
ECh
[7:0] = div [15:8] (LP_DIV)
Divider Register Byte 2
9132h
0Ah
[3:0] = div [19:16] (LP_DIV)
Frequency Trim
9133h
00h
Notes:
1) If illegal values (i.e. not defined in the following tables, e.g. ‘0’, no BCD code, not correct last day of month,
not correct leap year) are written to the time/date registers (9000h – 9006h), they are corrected to the first
valid number (‘automatic correction’)! Then an interrupt is generated and the TSA flag in the Control/Status
2 register is set.
2) All other registers are not corrected (e.g. alarm info incorrect Æ alarm is not met).
3) After power-up of VDD_BAT the time/date registers are stopped, the WAIT flag (Control/Status 1) is set.
4) Unused addresses will simply be ignored.
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Data Sheet AS8267 / AS8268
Control / Status 1 Register (9110h)
MSB
LSB
-
Bit
-
-
WAIT
-
-
-
-
Symbol Function
7
-
Not used
6
-
Not used
5
-
Not used
4
WAIT
3
-
Not used
2
-
Not used
1
-
Not used
0
-
Not used
Indicates that RTC is waiting for a start signal. The start signal is WAIT being reset to 0.
WAIT = 0 Î RTC running normally. (Clear by MCU.)
WAIT = 1 Î Is set when time/calendar information is changed (access to registers 9100h to 9106h).
While RTC is waiting for a start signal, 1Hz clock is still gated to the MPIOs.
Register bit assignment: (Unassigned bits in the registers are marked with ‘-‘. If these bits are read they will
return zero value. Writing these bits has no effect.)
Control / Status 2 Register (9111h)
MSB
LSB
TSA
Bit
7
-
A2F
A1F
STF
AIE2
AIE1
SIE
Symbol Function
TSA
Time Setting Alarm: Indicates when an impossible time/date has been set and it has been corrected by
st
st
the RTC automatically, e.g. 31 February Æ 1 February.
An interrupt will be generated and TSA is set to 1. The interrupt is cleared by setting TSA=0 (done by
MCU (software)).
6
-
Not used
5
A2F
Set to logic 1 when an alarm 2 occurs and maintains this value until software clears it. Indicates the
source of the interrupt. Cannot be set by software. When the flag is cleared, also the interrupt is cleared.
4
A1F
Set to logic 1 when an alarm 1 occurs and maintains this value until software clears it. Indicates the
source of the interrupt. Cannot be set by software. When the flag is cleared, also the interrupt is cleared.
3
STF
Set to logic 1 when a seconds timer interrupt occurs and maintains this value until software clears it.
Indicates the source of the interrupt. Cannot be set by software. When the flag is cleared, also the
interrupt is cleared.
2
AIE2
AIE2 = 0; alarm 2 interrupt disabled
AIE2 = 1; alarm 2 interrupt enabled
1
AIE1
AIE1 = 0; alarm 1 interrupt disabled
AIE1 = 1; alarm 1 interrupt enabled
0
SIE
SIE = 0; seconds counter interrupt disabled
SIE = 1; seconds counter interrupt enabled
Note: Alarm interrupts are only generated on rising clk_1hz edges (using system clock for detection). This
means that enabling an alarm after that will not generate an interrupt.
Revision 1.0, 19-Jun-07
Page 43 of 136
Data Sheet AS8267 / AS8268
Seconds / VL Register (9100h)
MSB
LSB
VL
Bit
sec.6
sec.5
sec.4
sec.3
sec.2
sec.1
sec.0
Symbol Function
7
VL
VL = 0; reliable clock / calendar information guaranteed.
VL = 1; clock / calendar information is NOT guaranteed.
This bit is set after power-up of VDD_BAT. It can be cleared by software only.
6
sec.6
5
sec.5
4
sec.4
3
sec.3
2
sec.2
1
sec.1
0
sec.0
These bits represent current seconds value encoded in BCD format (values from 0 to 59).
Minutes Register (9101h)
MSB
0
LSB
min.6
min.5
min.4
min.3
min.2
min.1
min.0
These bits represent current minute value encoded in BCD format (values from 0 to 59).
Hours Register (9102h)
MSB
0
LSB
0
hour.5
hour.4
hour.3
hour.2
hour.1
hour.0
These bits represent the current hours value encoded in BCD format (values from 0 to 23).
Days Register (9103h)
MSB
0
LSB
0
day.5
day.4
day.3
day.2
day.1
day.0
These bits represent current day value encoded in BCD format (values from 1 to 31).
Note on leap years: ‘00’ years in general are no leap years unless the complete year can be divided by 400
(e.g. 2000). Since the year 2000 has passed already, this chip will not consider a leap year for ‘00’ years.
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Data Sheet AS8267 / AS8268
Day of the Week Register (9104h)
MSB
LSB
0
0
0
Bit
Symbol
Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
-
Not used
2
weekd.2
1
0
0
weekd.2
These bits represent the current weekday value.
weekd.1
0
weekd.0
weekd.1
weekd.0
Bit2
Bit1
Bit0
Day
0
0
0
Sunday
0
0
1
Monday
0
1
0
Tuesday
0
1
1
Wednesday
1
0
0
Thursday
1
0
1
Friday
1
1
0
Saturday
Month / Century Register (9105h)
MSB
LSB
C
0
Bit
Symbol
7
C
0
month.4
month.3
month.2
month.1
month.0
Function
Century bit.
C = 0; indicates the year is 20xx
C = 1; indicates the year is 21xx
‘xx’ indicates the value held in Years register.
This bit is modified when Years register overflows from 99 to 00.
6
-
Not used
5
-
Not used
4
month.4
3
month.3
Revision 1.0, 19-Jun-07
These bits represent the current
month value encoded in BCD format.
Bit4
Bit3
Bit2
Bit1
Bit0
Month
0
0
0
0
1
January
0
0
0
1
0
February
0
0
0
1
1
March
0
0
1
0
0
April
0
0
1
0
1
May
Page 45 of 136
Data Sheet AS8267 / AS8268
Bit
Symbol
2
month.2
1
0
Function
month.1
month.0
0
0
1
1
0
June
0
0
1
1
1
July
0
1
0
0
0
August
0
1
0
0
1
September
1
0
0
0
0
October
1
0
0
0
1
November
1
0
0
1
0
December
Year Register (9106h)
MSB
year.7
LSB
year.6
year.5
year.4
year.3
year.2
year.1
year.0
These bits represent current year value encoded in BCD format (value from 0 to 99).
The Alarm 1 or 2 is generated when the programmed time has been reached (seconds = 0!).
Minute Alarm Register (1/2) (9114h/9119h)
MSB
0
LSB
mina.6
mina.5
mina.4
mina.3
mina.2
mina.1
mina.0
These bits represent minute alarm information encoded in BCD format (values from 0 to 59).
Hour Alarm Register (1/2) (9115h/911Ah)
MSB
0
LSB
0
houra.5
houra.4
houra.3
houra.2
houra.1
houra.0
These bits represent hour alarm information encoded in BCD format (values from 0 to 23).
Day Alarm Register (1/2) (9116h/911Bh)
MSB
0
LSB
0
daya.5
daya.4
daya.3
daya.2
daya.1
daya.0
These bits represent day alarm information encoded in BCD format (values from 1 to 31).
Month / Century Alarm Register (1/2) (9117h/911Ch)
MSB
C
LSB
0
0
mona.4
mona.3
mona.2
mona.1
mona.0
These bits represent current month alarm value encoded in BCD format (value from 1 to 12). Please see also
the ‘month assignments’ table above.
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Data Sheet AS8267 / AS8268
Year Alarm Register (1/2) (9118h/911Dh)
MSB
yeara.7
LSB
yeara.6
yeara.5
yeara.4
yeara.3
yeara.2
yeara.1
yeara.0
These bits represent the year alarm value encoded in BCD format (value from 0 to 99).
Setting the Time
The time can be set by writing to the respective time and calendar registers. When this is done the clock stops,
the WAIT bit is set and the control waits for the WAIT bit to be reset.
When the WAIT bit is reset the clock gate will be opened and the RTC starts running.
Alarms
When time and one of the alarm registers match (seconds = 0), an interrupt is generated. The source of the
interrupt is indicated in the A[1|2]F register bits in the Control/Status 2 register.
The alarm generation can be disabled using the AIE1/2 bits.
When the rest of the chip is off, there is no clock for the MCU interface, hence no alarm will be generated.
The MCU interface is reset with the ‘res’ signal which is coming from the PSM, i.e. all Status 2 bits are reset to
default, which means that after MCU power-up it has to set the appropriate alarms again. (After power-up the
MCU has to check what the time is, and has to decide what the next appropriate alarms will be.)
Seconds Timer (9112h, 9113h)
The seconds counter block, if enabled (SIE bit of Control/Status 2 register), generates an interrupt every n
seconds. ‘n’ is the number of seconds specified in the Seconds Timer registers 9112h (Byte 0) and 9113h (Byte
1). When an interrupt is sent, the flag STF is set.
The Seconds Timer register is not BCD coded.
Seconds counter start value:
Seconds counter count direction:
Condition for interrupt generation:
0000h
up
Seconds counter register value = Seconds Timer register value
Note: 0000h in the timer register means that no interrupt must be generated.
RTC Calibration (clk_1Hz)
When using the real-time clock (RTC) it is essential that the 1Hz signal to the real-time clock is accurate. There
are many possible external influences on the crystal oscillator frequency including the absolute crystal
frequency itself and the parasitic and oscillator capacitor values.
These influences alone can contribute to a significant change in the oscillator frequency. In this case, it is
necessary to perform a calibration of the 1Hz signal through the ‘Programmable Divider’ located in the 'Low
Power Divider'.
The procedure for trimming the RTC via the 'Programmable Divider' is explained below:
Assuming a crystal frequency of 3.579545 MHz
Revision 1.0, 19-Jun-07
Page 47 of 136
Data Sheet AS8267 / AS8268
The Programmable Divider follows a fixed 'Divide by 5' divider, thus the default value to the Programmable
Divider is:
3.579545 / 5 = 715909 (default value to Programmable Divider)
Therefore: A change of 1Hz in this default value is equal to:
1 / 715909 = 1.397 ppm
Measure the deviation in the clk_1Hz frequency output provided by the AS8267 / AS8268 ICs
Assuming an error of +690 ppm is measured (faster than real-time)
Thus +690 / 1.397 = 493.915 ≅ 494
Therefore 494 must be added to the default value:
715908 + 494 = 716402 (dec) = 0A EE 72 (hex)
Divider Register Byte 2 = 0A
Divider Register Byte 1 = EE
Divider Register Byte 0 = 72
The RTC is then calibrated to within +/- 1.4 ppm
Frequency Trimming (9133h)
A further option for clk_1Hz frequency trimming is available. In this case only the 5 lower bits of register
‘Frequency Trim’ (9133h) are used as defined in the following table.
FREQ_TRIM[4:0] Correction [ppm]
Seconds per Day 1
Seconds per Day 2
0
1
1
1
1
87.0
7
8
0
1
1
1
0
81.2
7
7
0
1
1
0
1
75.4
6
7
0
1
1
0
0
69.6
6
6
0
1
0
1
1
63.8
5
6
0
1
0
1
0
58.0
5
5
0
1
0
0
1
52.2
4
5
0
1
0
0
0
46.4
4
4
0
0
1
1
1
40.6
3
4
0
0
1
1
0
34.8
3
3
0
0
1
0
1
29.0
2
3
0
0
1
0
0
23.2
2
2
0
0
0
1
1
17.4
1
2
0
0
0
1
0
11.6
1
1
0
0
0
0
1
5.8
0
1
0
0
0
0
0
0
0
0
1
1
1
1
1
-5.8
0
-1
1
1
1
1
0
-11.6
-1
-1
1
1
1
0
1
-17.4
-1
-2
1
1
1
0
0
-23.2
-2
-2
1
1
0
1
1
-29.0
-2
-3
Revision 1.0, 19-Jun-07
Page 48 of 136
Data Sheet AS8267 / AS8268
FREQ_TRIM[4:0] Correction [ppm]
Seconds per Day 1
Seconds per Day 2
1
1
0
1
0
-34.8
-3
-3
1
1
0
0
1
-40.6
-3
-4
1
1
0
0
0
-46.4
-4
-4
1
0
1
1
1
-52.2
-4
-5
1
0
1
1
0
-58.0
-5
-5
1
0
1
0
1
-63.8
-5
-6
1
0
1
0
0
-69.6
-6
-6
1
0
0
1
1
-75.4
-6
-7
1
0
0
1
0
-81.2
-7
-7
1
0
0
0
1
-87.0
-7
-8
1
0
0
0
0
-92.8
-8
-8
The table specifies 2 successive days with (possibly) a different number of seconds that have to be added or
subtracted per day. ‘day1/day2’ are repeated continuously.
The RTC is always adjusted at the same time: 00:00 a.m. and 30 seconds . (The 30 seconds is required to
avoid conflicts with alarm settings, which are defined to occur at 0 seconds.)
Subtraction means that the specified number of 1Hz pulses is ignored. This has the effect that the clock stands
still for the specified number of seconds.
Example: A crystal has a frequency that is 30ppm higher than specified. Therefore the RTC will run faster.
Thus, the RTC has to correct in the negative direction, by subtracting seconds. Value ‘11011’ (-29.0) will be
chosen which means that on day1, 2 seconds are subtracted, then on the next day 3 seconds are subtracted,
then 2 seconds again and so on.
Battery Backup Operation
The AS8267 / AS8268 ICs contain a real-time clock (RTC) circuit, which must continue to operate even when
the mains supply voltage (V mains ) is interrupted. A battery backup facility is provided for this purpose at pin
VDD_BAT.
The low power oscillator (LP_OSC), low power divider (LP_DIV) and the real time clock (RTC) are all supplied
from the VDD_BAT pin.
The recommended battery backup circuit is shown below. The battery is connected to the VDD_BAT pin via one
or two diodes. The external VDD is also connected to the VDD_BAT pin via a diode, with the battery backup
only providing supply to the AS8267 / AS8268 ICs when the external VDD is interrupted.
+
external
VDD
VDD_BAT
Revision 1.0, 19-Jun-07
Page 49 of 136
Data Sheet AS8267 / AS8268
8.2
Temperature Sensor
The AS8267 / AS8268 ICs include an on-chip temperature sensor which allows for temperature correction over
the entire operating temperature range of the device:
Parameter
Symbol
Min
Typ
Max
Unit
Note
Absolute Error (trimmed)
-5
+5
°C
from -40°C to 85°C
Relative Error (trimmed)
-2
+2
°C
from -40°C to 85°C
Temperature Range
-40
85
°C
Resolution
0.193
°C/LSB
Note:
The temperature sensor is activated by the MCU for a single measurement.
A temperature measurement is initiated by setting the measure bit in the TS_Status register to 1. The result of
the measurement is then available in the TS_Result0/TS_Result1 register.
The registers TS_OffsetCorr0/TS_OffsetCorr1 hold the offset correction value which is derived during
production process.
The actual temperature value is calculated by the means of the following formula:
Temp [°C] = ( Temp _ corrected × 0.193 ) − 75
with Temp_corre cted = TS_Result [15 : 0] + TS_OffsetC orr [15 : 0]
Register Name
Address
Reset Value
TS_Status
9600h
00h
TS_Result0
9601h
00h
TS_Result1
9602h
00h
TS_OffsetCorr0
9603h
00h
TS_OffsetCorr1
9604h
00h
Note
TS_Status (9600h)
MSB
LSB
0
Note:
MEASURE:
0
0
0
0
0
0
Measure
- flag is set by the MCU and reset by the temperature sensor itself.
0: no operation; or: temperature measurement finished
1: if set by MCU the measurement starts; or: indicates an ongoing measurement
TS_Result0/TS_Result1 (9601h/9602h)
TS_Result0
MSB
D7
Revision 1.0, 19-Jun-07
LSB
D6
D5
D4
D3
D2
D1
D0
Page 50 of 136
Data Sheet AS8267 / AS8268
TS_Result1
MSB
LSB
0
0
0
0
0
0
D9
D8
OC3
OC2
OC1
OC0
TS_OffsetCorr0/TS_OffsetCorr1 (9603h/9604h)
Signed offset correction value [15:0]; read only.
TS_OffsetCorr0
MSB
OC7
LSB
OC6
OC5
OC4
TS_OffsetCorr1
MSB
OC15
LSB
OC14
OC13
OC12
OC11
OC10
OC9
OC8
Example for temperature calculation:
Temp [°C] = ( Temp _ corrected × 0.193 ) − 75
with Temp_corre cted = TS_Result [15 : 0] + TS_OffsetC orr [15 : 0]
TS_Result[15:0]
= 00A2h
TS_OffsetCorr[15:0]
= 0101h
Temp_corrected = 01A3h = 419d
Temp[°C] = (419 × 0.193) – 75 = 5.9[°C]
Revision 1.0, 19-Jun-07
Page 51 of 136
Data Sheet AS8267 / AS8268
8.3
LCD Driver (LCDD)
selvlcd
VDD
lcdd_pd
LBP0
VREG
Voltage
Level
Generation
LCD
Drive
LBP1
LBP2
LBP3
LSD0
LSD23
VSS
LCDD
Control
Data
Register1
Data
Register2
MCU
Figure 6:
LCD driver block diagram
The on-chip LCD driver (LCDD) is a peripheral block, which interfaces to almost any liquid crystal display
(LCD) having a multiplex rate of 4. It generates the drive signals to directly drive multiplexed LCDs containing
up to four backplanes and up to 24 segments per backplane. The AS8267 has a 20 x 4 LCDD, while the
AS8268 has a 24 x 4 LCDD.
The data registers receive and store the display information, which is to be sent to the display. The LCDD
control block decodes the information into the select lines for the single segments using a specific timing.
The LCD voltage can be selected to adjust the contrast of the display, as required. The selvlcd[2:0] register
bits enable the setting of the LCD contrast by selecting one of the defined LCD voltage levels. The contrast can
be improved with a higher voltage, however the contrast is also dependent upon the crystal frequency.
With the lcdd_pd bit the LCDD analog part can be switched off.
Revision 1.0, 19-Jun-07
Page 52 of 136
Data Sheet AS8267 / AS8268
Typical Display
The LCD above is a typical example of those used in electricity meter applications and consists of a number of
digits (generally up to 8 digits) including decimal points. Typically, annunciators (‘kWh’, ‘Volt’, etc.) are also
included to signify the type of data on display.
LCD Drive (LCD_DRIVE)
LCD drive mode is 1/4duty, 1/3bias.
4 back planes
- 24 segment drives (maximum)
All other parameters are listed in the table below:
-
Parameter
Symbol
Min
Typ
Max
Unit
LCD frame frequency
fLCD
33
39.4
44
Hz
LCD voltage
VLCD
2.3
2.5
2.75
V
V3
0.95 x VLCD
VLCD
1.05 x VLCD
V
LCD segment and back
plane drive voltages
LCD DC component
V2
0.95 x 2/3VLCD 2/3VLCD 1.05 x 2/3VLCD
V
V1
0.95 x 1/3VLCD 1/3VLCD 1.05 x 1/3VLCD
V
V0
VSS
VDCLCD
-20
0
20
mV
LCD drive impedance
RLCD
100
kΩ
LCD load on each driver pin
Cload
300
pF
Notes
1)
for selvlcd=’000’
Note:
1) These frequencies are derived from the master clock (3MHz; 3.58MHz; 4MHz) using a divider of 90,909.
Revision 1.0, 19-Jun-07
Page 53 of 136
Data Sheet AS8267 / AS8268
LCDD Control (LCDD_CTRL) including Input and Config Registers
In the control block of the LCD driver there are two registers. Each of these registers may contain data to be
displayed. With a special bit (921Eh, bit 0), it is possible to select one of the two register banks for display.
Each register defines the settings for the different segment and plane select lines. The following table specifies
the allocation of the register bits:
LSD0
LSD1
LSD2
LSD3
LSD4
LSD5
LSD6
LSD7
LSD8
LSD9
LBP0
reg[0]
reg[4]
reg[8]
reg[12]
reg[16]
reg[20]
reg[24]
reg[28]
reg[32]
reg[36]
LBP1
reg[1]
reg[5]
reg[9]
reg[13]
reg[17]
reg[21]
reg[25]
reg[29]
reg[33]
reg[37]
LBP2
reg[2]
reg[6]
reg[10]
reg[14]
reg[18]
reg[22]
reg[26]
reg[30]
reg[34]
reg[38]
LBP3
reg[3]
reg[7]
reg[11]
reg[15]
reg[19]
reg[23]
reg[27]
reg[31]
reg[35]
reg[39]
LSD10
LSD11
LSD12
LSD13
LSD14
LSD15
LSD16
LSD17
LSD18
LSD19
LBP0
reg[40]
reg[44]
reg[48]
reg[52]
reg[56]
reg[60]
reg[64]
reg[68]
reg[72]
reg[76]
LBP1
reg[41]
reg[45]
reg[49]
reg[53]
reg[57]
reg[61]
reg[65]
reg[69]
reg[73]
reg[77]
LBP2
reg[42]
reg[46]
reg[50]
reg[54]
reg[58]
reg[62]
reg[66]
reg[70]
reg[74]
reg[78]
LBP3
reg[43]
reg[47]
reg[51]
reg[55]
reg[59]
reg[63]
reg[67]
reg[71]
reg[75]
reg[79]
LSD20
LSD21
LSD22
LSD23
LBP0
reg[80]
reg[84]
reg[88]
reg[92]
LBP1
reg[81]
reg[85]
reg[89]
reg[93]
LBP2
reg[82]
reg[86]
reg[90]
reg[94]
LBP3
reg[83]
reg[87]
reg[91]
reg[95]
AS8268 only
Notes:
1) Each of the register bits represents one of the segments of the digits or a decimal point or one of the
annunciators.
2) reg[x]=0: Segment is turned off; reg[x]=1: Segment is turned on.
Revision 1.0, 19-Jun-07
Page 54 of 136
Data Sheet AS8267 / AS8268
The complete register is organized in bytes according to following table:
Register Name
Address
Reset Value
Description
reg1[7:0]
9200h
00h
reg1[15:8]
9201h
00h
reg1[23:16]
9202h
00h
reg1[31:24]
9203h
00h
reg1[39:32]
9204h
00h
reg1[47:40]
9205h
00h
reg1[55:48]
9206h
00h
reg1[63:56]
9207h
00h
reg1[71:64]
9208h
00h
reg1[79:72]
9209h
00h
reg1[87:80]
920Ah
00h
reg1[95:88]
920Bh
00h
reg2[7:0]
9210h
00h
reg2[15:8]
9211h
00h
reg2[23:16]
9212h
00h
reg2[31:24]
9213h
00h
reg2[39:32]
9214h
00h
reg2[47:40]
9215h
00h
reg2[55:48]
9216h
00h
reg2[63:56]
9217h
00h
reg2[71:64]
9218h
00h
reg2[79:72]
9219h
00h
reg2[87:80]
921Ah
00h
reg2[95:88]
921Bh
00h
use_reg
921Eh
00h
Bit 0: Selects register to be used.
0: Data Register 1
1: Data Register 2
selvlcd[2:0]
921Fh
00h
Select VLCD level. See table in LCD Voltage Select
Register.
lcdd_pd
9220h
01h
Bit 0: Power-down of the LCDD analog part.
0: Display on
1: Display off
AS8268 only
AS8268 only
Notes:
1) Unused registers will simply be ignored.
2) All the registers are write only. Read operations always return 0.
Revision 1.0, 19-Jun-07
Page 55 of 136
Data Sheet AS8267 / AS8268
LCD Display Data Select Register (USE_REG, 921Eh)
The use_reg register selects either Data Register 1 or Data Register 2 for display on the LCD. Select ‘0’ for
Data Register 1 and ‘1’ for Data Register 2.
MSB
LSB
-
-
-
-
-
-
-
use_reg
LCD Voltage Select Register (SELVLCD, 921Fh)
The LCD voltage select register, SELVLCD enables variation of the LCD contrast by selecting on of the 8 preset voltage levels.
MSB
LSB
-
-
-
Bit
Symbol
Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
-
Not used
2
selvlcd.2
1
-
-
selvlcd.2
These bits set the LCD voltage level for the LCD
contrast setting.
selvlcd.1
0
selvlcd.0
selvlcd.1
selvlcd.0
Bit2
Bit1
Bit0
VLCD
0
0
0
2.5V
0
0
1
2.5714V
0
1
0
2.6428V
0
1
1
2.7142V
1
0
0
2.7856V
1
0
1
2.8570V
1
1
0
2.9284V
1
1
1
3.0V
LCD Power-Down (LCDD_PD, 9220h)
The lcdd_pd register enables the analog part of the LCDD to be powered-down. Select ‘0’ for LCD display on
and ‘1’ for LCD display off.
MSB
-
Revision 1.0, 19-Jun-07
LSB
-
-
-
-
-
-
lcdd_pd
Page 56 of 136
Data Sheet AS8267 / AS8268
8.4
Programmable Multi-Purpose I/Os (MPIO)
sel_pupd
en_io
sel_drv
Config Register
sel_in
en_io0
UART2
InputMultiplexer
[11:0]
rxd2
txd2
out_io0
IO0
in_io0
DATA
REGISTERS
MCU
Input
Register
[11:0]
out_mux
Output
Register
[11:0]
led
clk_1hz
sel0_io[x]
sel1_io[x]
register[x]
led
txd2
clk_1hz
Output
Multiplexer
[11:0]
IO11
Pulse
Counter
out_io[x]
[11:0]
sel_refp
Figure 7:
MPIO block diagram
A total of 9 bidirectional multi-purpose I/O pins (MPIO) are provided with the AS8267 and 12 bidirectional multipurpose I/O pins with the AS8268, which may be used for a variety of purposes. All the I/Os can be freely
programmed as inputs or outputs, with the option of either a pull-up or pull-down resistor. The drive strength of
the individual I/O pins may also be programmed. On start-up all the I/O pins are disabled.
Furthermore, a pulse counter is available, which can be used for calibration purposes (‘comparison calibration
method’: Between two LED pulses the pulses from a reference meter with much higher pulse rate are counted.
The result is used to calculate the calibration factor.).
MPIO Registers
All the MPIO registers are listed in the table below. The individual register functions are then described in
detail.
Register Name
Address
Reset Value
MAKE_IRQ0
9500h
00h
MAKE_IRQ1
9501h
00h
OUT_MUX0
9502h
00h
OUT_MUX1
9503h
00h
Notes
Config
Revision 1.0, 19-Jun-07
Page 57 of 136
Data Sheet AS8267 / AS8268
Register Name
Address
Reset Value
OUT_MUX2
9504h
00h
SET_EN0
9505h
00h
SET_EN1
9506h
00h
SEL_DRV0
9507h
00h
SEL_DRV1
9508h
00h
SEL_PUPD0
9509h
00h
SEL_PUPD1
950Ah
00h
SEL_IN_RXD2
950Bh
04h
SEL_IN_REFP
950Ch
03h
IN0
950Dh
00h
IN1
950Eh
00h
OUT0
950Fh
00h
OUT1
9510h
00h
OUT2
9511h
00h
OUT3
9512h
00h
OUT4
9513h
00h
OUT5
9514h
00h
OUT6
9515h
00h
OUT7
9516h
00h
OUT8
9517h
00h
OUT9
9518h
00h
OUT10
9519h
00h
OUT11
951Ah
00h
PCNT0
951Bh
00h
PCNT1
951Ch
00h
PCNT2
951Dh
00h
STATUS0
951Eh
00h
STATUS1
951Fh
00h
Notes
Input
Output
AS8268 only
Pulse counter
Status
Note: Unused addresses are ignored.
Revision 1.0, 19-Jun-07
Page 58 of 136
Data Sheet AS8267 / AS8268
MAKE_IRQ0/MAKE_IRQ1 (9500h/9501h)
The MAKE_IRQ registers specify if an interrupt should be generated after the related I/O input has changed.
The I/O pin, which caused the interrupt, will be indicated in the STATUS0/STATUS1 flag registers.
IOx:
0:
no interrupt on signal change
1:
generate an interrupt on signal change
MAKE_IRQ0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
MAKE_IRQ1
MSB
IO0
LSB
0
0
0
0
IO11
IO10
IO9
IO8
AS8268 only
OUT_MUX0/OUT_MUX1/OUT_MUX2 (9502h/9503h/9504h)
The OUT_MUX registers specify the source signal for each of the I/O outputs. Every 2 bits are used as select
signals for the 4-way output multiplexer of the designated I/O.
OUT_MUX0
MSB
IO3: sel1
LSB
IO3: sel0
IO2: sel1
IO2: sel0
IO1: sel1
IO1: sel0
IO0: sel1
IO0: sel0
OUT_MUX1
MSB
IO7: sel1
LSB
IO7: sel0
IO6: sel1
IO6: sel0
IO5: sel1
IO5: sel0
IO4: sel1
IO4: sel0
OUT_MUX2
MSB
IO11: sel1
LSB
IO11: sel0
IO10: sel1
IO10: sel0
IO9: sel1
IO9: sel0
IO8: sel1
IO8: sel0
AS8268 only
The following table shows the settings for the output signal options:
sel1
sel0
0
0
register[x]
0
1
led
1
0
txd2
1
1
clk_1hz
Revision 1.0, 19-Jun-07
Output Signal Notes
80ms pulse width
Page 59 of 136
Data Sheet AS8267 / AS8268
SET_EN0/SET_EN1 (9505h/9506h)
The SET_EN registers set the en_io signal of the related I/O pin. The en_io enables the tri-state output buffer
so that the I/O pins operate as outputs.
IOx:
0:
disable output (I/O used as input)
1:
enable output
SET_EN0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
0
0
0
IO11
IO10
IO9
IO0
SET_EN1
MSB
LSB
0
IO8
AS8268 only
SEL_DRV0/SEL_DRV1 (9507h/9508h)
The SEL_DRV registers select the current drive strength for all the I/Os that have been selected as outputs:
IOx:
0:
4mA
1:
8mA
SEL_DRV0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
IO0
SEL_DRV1
MSB
LSB
0
0
0
0
IO11
IO10
IO9
IO8
AS8268 only
SEL_PUPD0/SEL_PUPD1 (9509h/950Ah)
The SEL_PUPD registers select either a pull-up or pull-down resistor for each of the I/O pins:
IOx:
0: pull-down
1:
pull-up
SEL_PUPD0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
0
0
0
IO11
IO10
IO9
IO0
SEL_PUPD1
MSB
0
LSB
IO8
AS8268 only
Revision 1.0, 19-Jun-07
Page 60 of 136
Data Sheet AS8267 / AS8268
SEL_IN_RXD2 (950Bh)
The SEL_IN_RXD2 register selects which I/O input is used for the special input signal ‘rxd2’ (UART2 receive
input). Any one of the I/Os from IO0 to IO11 may be selected for this purpose.
The select bits are defined in the following table:
MSB
0
LSB
0
0
0
sel3
sel2
sel1
LSB
Input
0
0
0
0
0
0
0
0
IO0
0
0
0
0
0
0
0
1
IO1
0
0
0
0
0
0
1
0
IO2
0
0
0
0
0
0
1
1
IO3
0
0
0
0
0
1
0
0
IO4
0
0
0
0
0
1
0
1
IO5
0
0
0
0
0
1
1
0
IO6
0
0
0
0
0
1
1
1
IO7
0
0
0
0
1
0
0
0
IO8
0
0
0
0
1
0
0
1
IO9
0
0
0
0
1
0
1
0
IO10
0
0
0
0
1
0
1
1
IO11
MSB
sel0
AS8268 only
SEL_IN_REFP (950Ch)
The SEL_IN_REFP register selects which I/O input is to be used for reference pulses. Any one of the I/Os from
IO0 to IO11 may be selected for this purpose.
The select bits are defined in the following table:
MSB
0
LSB
0
0
0
sel3
sel2
sel1
MSB
sel0
LSB
Input
0
0
0
0
0
0
0
0
IO0
0
0
0
0
0
0
0
1
IO1
0
0
0
0
0
0
1
0
IO2
0
0
0
0
0
0
1
1
IO3
0
0
0
0
0
1
0
0
IO4
0
0
0
0
0
1
0
1
IO5
0
0
0
0
0
1
1
0
IO6
Revision 1.0, 19-Jun-07
Page 61 of 136
Data Sheet AS8267 / AS8268
MSB
LSB
Input
0
0
0
0
0
1
1
1
IO7
0
0
0
0
1
0
0
0
IO8
0
0
0
0
1
0
0
1
IO9
0
0
0
0
1
0
1
0
IO10
0
0
0
0
1
0
1
1
IO11
AS8268 only
IN0/IN1 (950Dh/950Eh)
The IN registers (input registers) store the input data from the I/O pins. These registers are continuously
updated by the ‘Mclk’ (main clock).
IN0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
IO0
IN1
MSB
0
LSB
0
0
0
IO11
IO10
IO9
IO8
AS8268 only
OUT0 … OUT11 (950Fh – 951Ah)
The OUT registers (output registers) contain the output data to be sent to the I/O pins (through the
multiplexers).
OUT0
MSB
0
LSB
0
0
0
0
0
0
0
0
0
0
0
0
IO0
OUT1
MSB
0
LSB
IO1
OUT2
MSB
0
LSB
0
0
0
0
0
0
IO2
OUT3
MSB
0
Revision 1.0, 19-Jun-07
LSB
0
0
0
0
0
0
IO3
Page 62 of 136
Data Sheet AS8267 / AS8268
OUT4
MSB
LSB
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
IO4
OUT5
MSB
LSB
0
IO5
OUT6
MSB
LSB
0
IO6
OUT7
MSB
LSB
0
0
0
0
0
0
0
IO7
OUT8
MSB
LSB
0
0
0
0
0
0
0
IO8
OUT9
MSB
LSB
0
0
0
0
0
0
0
IO9
0
0
0
IO10
AS8268 only
OUT10
MSB
LSB
0
0
0
0
AS8268 only
OUT11
MSB
LSB
0
0
0
0
0
0
0
IO11
AS8268 only
PCNT0/PCNT1/PCNT2 (951Bh/951Ch/951Dh)
The PCNT registers (pulse counter registers) contain the result of the pulse counting for calibration purposes.
PCNT0
MSB
b7
LSB
b6
Revision 1.0, 19-Jun-07
b5
b4
b3
b2
b1
b0
Page 63 of 136
Data Sheet AS8267 / AS8268
PCNT1
MSB
b15
LSB
b14
b13
b12
b11
b10
b9
b22
b21
b20
b19
b18
b17
b8
PCNT2
MSB
b23
LSB
b16
The maximum reference pulse frequency is defined below:
Parameter
Symbol
Reference pulse frequency
Min
Typ
frefp
Max
Unit
120
kHz
Notes
STATUS0/STATUS1 (951Eh/951Fh)
The STATUS registers contain the irq flag register bits for each of the I/Os, the COUNT register bit which
signals when a pulse counting should be started and the CINT flag bit which indicates when pulse counting has
been completed.
The irq flag registers are cleared by software only (MCU), but they cannot be set by software.
The COUNT register bit can be set and reset by software (MCU). The COUNT register bit is cleared, when the
pulse counter is finished and an interrupt has been generated.
STATUS0
MSB
IO7
LSB
IO6
IO5
IO4
IO3
IO2
IO1
IO0
STATUS1
MSB
COUNT
LSB
CINT
0
0
IO11
IO10
IO9
IO8
AS8268 only
Notes:
1) IOx:
0:
no change on input x
1:
input x has changed
2) When an interrupt on an IO change has been generated, the signal irq is reset after the related flag has
been cleared.
3) CINT is a flag, which indicates that the pulse counting has finished. When CINT is cleared, the irq is
cleared.
Revision 1.0, 19-Jun-07
Page 64 of 136
Data Sheet AS8267 / AS8268
Pulse Counter
A synchronous pulse counter is used. It is started after the COUNT bit has been set. The first led pulse is used
for synchronisation. The second led pulse starts counting the reference pulses from the specified I/O input.
Timing:
COUNT
led
Gate
refp
counted refp
CINT
Notes:
1) The COUNT signal is synchronized with ‘led’.
2) COUNT is reset and CINT is set using clk and checking for falling edge on Gate.
3) The PCNT register is only updated when counting is finished.
Example:
Select IO3 as the pulse reference input.
Meter is 220V mains ; I max = 20A
Meter constant: 1,600imp/kWh
Reference meter constant: 16 million imp/kWh
Register settings:
MPIO SET_EN0
SEL_IN_REFP
DSP
mconst
(9505h):
(950Ch):
(9330h):
IO3 bit = 0 (output disabled)
02h
07h
(Ideal) Pulse_lev (932Ch – 932Ah) =
570,950 ×
230 V 40 A
×
220 V 20 A
= 1,193,804 ⇒ 12374Ch
⇒ 932Ah: 4Ch
932Bh: 37h
932Ch: 12h
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Procedure:
Status1 (951Fh): 80h → starts pulse counting.
When pulse counting is completed → CINT bit in Status1 = 1.
The status of the CINT bit in Status1 may be checked to confirm that the pulse counting is complete.
Alternatively, the time between 2 pulses may be calculated to determine the count cycle time (the first pulse is
used for synchronization and the second pulse starts the count cycle).
Following the pulse counting cycle, the number of pulses counted can be read from PCNT0/PCNT1/PCNT2
(951Bh/951Ch/951Dh).
The ideal number of pulses counted assuming the meter is perfectly calibrated would be:
Ni =
16,000,000
= 10,000
1,600
Assuming that we count 11,000 pulses, the (Ideal) Pulse_lev must be changed by the factor:
10,000/11,000 = 0.909
The new Pulse_lev
= 1,193,804 x 0.909
= 1,085,168 ⇒ 108EF0h
⇒ 932Ah: F0h
932Bh: 8Eh
932Ch: 10h
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
8.5
Serial Peripheral Interface (SPI)
The Serial Peripheral Interface (SPI) represents a synchronous, bit serial 4-wire interface for full-duplex data
transfer.
Depending on the operating mode (selectable by the sel_spi2 bit in the SCT enable signals register (9001h))
the interface can act as SPI2 Master/Slave interface (e.g. when an external EEPROM is connected) or as
SPI_FLASH interface (when used as interface to the Flash).
SPI
Interface
sel_spi2
=0
sel_spi2
=1
SPI_FLASH
SPI2
Master
Mode
Figure 8:
8.5.1.
Slave
Mode
SPI Interface
SPI2 Master/Slave Mode
In this mode the SPI can operate in master mode, whereas the external EEPROM works in slave mode.
The external EEPROM memory must fulfil the requirements described below. The EEPROM is selectable in
size from 1kByte to 32kByte in binary steps.
Key Features
-
Standard 4 wire synchronous serial interface (MISO, MOSI, SC, S_N)
Master/slave mode operation
8-bit word length (variable transmit/receive word optional)
Shift clock SC high when idle
MSB is always transmitted first
Four selectable clocking schemes (clock idle state / clock phase)
Selectable SPI clock rate divider (from mcu_clk/2 to mcu_clk/65536)
Three maskable interrupts (transmission complete, overrun, collision)
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Data Sheet AS8267 / AS8268
SPI Registers
Register Name
Address Description
SSPCON
9400h
Control register
SSPCLKDIV
9401h
Clock divider register
SSPSTAT
9402h
Status register
SSPBUF
9403h
Data register
Control Register (SSPCON, 9400h)
The control register is used for enabling the SPI-interrupts and to control the chip select of the SPI.
MSB
LSB
IETR
Bit
IEOV
IECO
IECS
CSO
-
AUTO
-
Symbol Function
7
IETR
Transmit interrupt enable
Issued after data register has been serially loaded with new data (slave mode) or if data has been
shifted out after write access (master mode)
0: disable
1: enable
6
IEOV
Overrun interrupt enable
Issued if ITRA still set and new data serially arrived
0: disable
1: enable
5
IECO
Write collision interrupt enable
Issued if data register is written during transmission
0: disable
1: enable
4
IECS
Chip select interrupt enable
Issued if chip-select pin is activated during master/slave mode
0: disable
1: enable
3
CSO
Chip select output state in master mode if AUTO = 0
Inverted state of output signal S_N
0: S_N = ‘1’
1: S_N = ‘0’ (active)
2
ISOUT Chip select output enable control in master mode
1
AUTO
0
-
1: Automatically activates the S_N (= ’0’) after data has been written to the data register and
deactivates S_N (= ’1’) after transfer completed
0: S_N depends on the CSO bit (→ manual S_N setting)
Not used
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Data Sheet AS8267 / AS8268
Clock Divider Register (SSPCLKDIV, 9401h)
The clock divider register contains control bits to configure the clock-divider, to set-up the serial-clock SC, to
enable the SPI and to select master or slave mode.
MSB
LSB
ENBL
CIDLE
Bit
Symbol
7
ENBL
6
CIDLE
CPHA
M/S
CPHA
3
2
1
0
CLKDIV.1
CLKDIV.0
SPI enable. Enables the SPI interface
1: enable
0: disable
Serial clock SC idle state
Serial clock SC phase
Data is samples and shifted out
according to CIDLE/CPHA
4
CLKDIV.2
Function
1: SC idles high
0: SC idles low
5
CLKDIV.3
CIDLE
Bit6
CPHA
Bit5
SC Idle
Data shifted Input sampled
out on SC
on SC
0
0
0
falling
rising
0
1
0
rising
falling
1
0
1
rising
falling
1
1
1
falling
rising
Note: The CIDLE/CPHA set at 1 1 is used internally by most
standard available EEPROMs
Master/Slave mode
1: Master mode, must be ‘1’
0: Slave mode
CLKDIV.3 Clock divider exponent
In master mode, SPI output clock SC is
CLKDIV+1
MCU_CLK / 2
M/S
CLKDIV.2
CLKDIV.1
CLKDIV.0
Bit3
Bit2
Bit1
Bit0
SC-Rate
0
0
0
0
1:2
0
0
0
1
1:4
0
0
1
0
1:8
0
0
1
1
1 : 16
0
1
0
0
1 : 32
0
0
0
1
1
1
1
1
0
0
0
1
1
0
0
1
0
1
0
1
1 : 64
1 : 128
1 : 256
1 : 512
1 : 1,024
1
0
1
0
1 : 2,048
1
0
1
1
1 : 4,096
1
1
0
0
1 : 8,192
1
1
0
1
1 : 16,384
1
1
1
0
1 : 32,768
1
1
1
1
1 : 65,536
The SPI output clock SC, which is derived from the mcu clock (mcu_clk) may be divided down as shown in the
table above.
It is important to note, that the mcu_clk may also be divided down as described under MCUCLKDIV Register
(‘mcu_clk’). Therefore the SPI output clock SC is also dependent on the programming of the mcu_clk
frequency.
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Recommended programming for 3.579545MHz mcu clock rate, SPI enabled, SC clock phase = ‘11’, master:
Value
SC Clock Rate
1.74MHz
F0h
0.895MHz
F1h
0.447MHz
F2h
Status Register (SSPSTAT, 9402h)
MSB
ITRA
Bit
IOVR
ICOL
-
CSI
-
-
LSB
-
Symbol Function
1
Transmission complete interrupt issued. Issued after new data word is available in data-register (slave
configuration), or if data-register has been shifted out after write access (master configuration)
1
Overrun interrupt issued. Issued if ITRA is still set from previous transmission and new data arrives
(master and slave configuration)
1
Write-collision interrupt issued. Issued if data-register is written during receive (slave configuration) or
transmit (master configuration)
7
ITRA
6
IOVR
5
ICOL
4
-
3
CSI
2
-
Not used
1
-
Not used
0
-
Not used
Not used
Always ‘0’, has no effect
Note:
1) Flag-bits change state independent of the state of the corresponding interrupt-enable bit of the control
register.
The SPI interrupt status is captured in the SSPSTAT register. Each interrupt status bit can be masked by the
SSPCON register, which is OR-ed to a single SPI interrupt request signal (SPI_IRQ).
MCU Register
SSPSTAT
SSPCON
IE
ITRA
IOVR
OR
SPI_IRQ
ICOL
IE.ESPI
(=IE.3)
IETR,
IEOV,
IECO
Figure 9:
Block diagram
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Data Register (SSPBUF, 9403h)
The data-register is an 8-bits wide shift-register with parallel load input and parallel output.
parallel
SPI_DATAIN
from MCU
serial out
7
6
5
4
3
2
1
0
Bit
serial in
MISO
MOSI
parallel out
SPI_DATAOUT
to MCU
EEPROM
S_N
SPI
Master
EEP_S_N
SC
EEP_SC
MOSI
EEP_SI
MISO
EEP_SO
3.3V
AS8267 /
AS8268
EEP_HOLD_N
EEP_WP_N
Figure 10: Typical SPI connection to an EEPROM
Many EEPROMs provide a HOLD_N (hold protocol) pin and a WP_N pin (write protect), which must be held ‘1’,
otherwise the operation is blocked.
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
8.5.2.
SPI_FLASH Mode
In this mode the SPI operates in slave mode, in which the interface is used to communicate with the internal
Flash memory.
The SPI_Flash block contains an 8-bit instruction register. It is accessed via the MISO pin, with data being
clocked in on the rising edge of SC. The S_N pin must be low. The table below contains the list of the possible
instruction bytes and format for SPI_Flash block operation. All instructions, addresses, and data are
transferred MSB first, LSB last. Data is sampled on the first rising edge of SC after S_N goes low.
Instruction Set
Instruction Name
Instruction
Code
Description
READ
03h
Read data from memory array beginning at selected address
PP
02h
Page Program, moves data to selected memory page
WREN
06h
Set write enable latch (enable write and erase operations)
WRDI
04h
Reset the write enable latch (disable write operations)
RDSR
05h
Read Flash status register (FLASH_STAT, 9700h)
WRSR
01h
Write Flash status register (FLASH_STAT, 9700h)
PE
D8h
Page Erase
ME
C7h
Mass Erase
RESET
E9h
Sets external reset pin (may be used to reset the whole device)
Functional Description
Arbitration
After a write, page erase or mass erase command the Flash memory is busy for some time and no command must be sent.
To handle concurrent access from MCU and the MCU independent interfaces (UART1, SPI via SPI_Flash) to the Flash
memory an arbitration procedure is necessary for the external interfaces:
1. Send a request to the Flash (Set REQ bit in FLASH_STAT register)
2. Poll status of Flash until Flash is ready (WIP bit in FLASH_STAT register must be 0)
-> Flash memory is reserved for external interface and MCU remains halted.
3. Send one or several Flash commands (Flash must not be busy before sending the next Flash command)
4. Release Flash request (Clear REQ bit in FLASH_STAT register)
-> MCU is running again
Request is needed for all Flash commands
Concurrent access of both MCU independent interfaces is not allowed.
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Read
The SPI_Flash is selected by pulling S_N low. The 8-bit read instruction is transmitted to the SPI_Flash followed by the 16-bit
address with the MSB (address[15]) of the address word being don’t care. After the correct read instruction and address are
sent, the data stored in the memory at the selected address is shifted out on the MOSI pin. (After an access time of 13
system clocks the Flash data is available in the SPI transit register). The data stored in the memory at the next address can
be read sequentially by continuing to provide clock pulses. The internal address pointer is automatically incremented to the
next higher address after each byte of data is shifted out. When the highest address is reached (7FFFh), the address counter
rolls over to address 0000h allowing the read cycle to be continued indefinitely. Rising the S_N pin terminates the read
operation.
Timing
S_N
0
1
2
3
4
5
6
7
8
9
10
11
21
22
23
2
1
0
24
25
26
7
6
5
27
28
29
30
31
2
1
0
SC
Instruction
MISO
0
0
0
0
0
16 Bit Address
0
1
1
15
14
13
12
Data Out
High Impedance
MOSI
4
3
Example Read FLASH Sequence
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
0x01
0x04
0x05
0x03
0x00
0x80
Dat0
Dat1
…
0x01
0x00
… … set REQ bit by writing 0x04 to status register
… -“… read Flash status register until Flash is ready
… read Flash instruction
… Start address, e.g. 80h
… -“… read byte 0 from address
… read byte 1 from address + 1
… read bytes as long as you want, after address overrun it restarts at address 0.
… clear REQ bit by writing 0x00 to status register
… -“-
Page Program
The whole memory of 32K bytes is split into 512 pages with 64 bytes per page. Each page can be written with 64 bytes at
once or, it can be written byte-wise or in groups of bytes. The addressing order is arbitrary. Prior to any attempt to write data
to the SPI_Flash or status register, the write enable latch must be set by issuing the WREN instruction. Setting S_N low and
then clocking out the proper instruction into the SPI_Flash does this. After all eight bits of the instruction are transmitted; the
S_N must be brought high to set the write enable latch. If the write operation is initiated immediately after the WREN
instruction without S_N being brought high, the data will not be written to the array because the write enable latch will not
have been properly set.
Once the write enable latch is set, the user may proceed by setting the S_N low, issuing a write instruction, followed by the
address, and then the data to be written. Up to 64 bytes of data can be sent to the SPI_Flash before a program cycle is
necessary. The only restriction is that all of the bytes must reside in the same page. An address consists of a page address
(9 bits) and the address in page (6 bits), where the page address = address [15:6] and the address in page is address [5:0]. If
the internal address counter reaches 0x7FFF and the clock continues, the counter will roll over to the first address 0x0000.
Revision 1.0, 19-Jun-07
Page 73 of 136
Data Sheet AS8267 / AS8268
th
For the data to be actually written, the S_N must be brought high after the least significant bit (D0) of the n data byte has
been clocked in. If S_N is brought high at any other time, the write operation will not be completed. While the write is in
progress, the status register may be read to check the status. A read attempt of a memory array location will not be possible
during a write cycle. When the write cycle is completed, the write enable latch is reset.
Byte Write
S_N
TWC
0
1
2
3
4
5
6
7
8
9
10
11
21
22
23
24
25
26
27
28
29
30
31
SC
Instruction
MISO
0
0
0
0
16 Bit Address
0
0
1
0
Data Byte
15
14
13
12
2
1
0
7
6
5
8
9
10
11
21
22
23
24
25
26
15
14
2
1
0
7
6
5
4
3
2
1
0
High Impedance
MOSI
Page Program (max. 64 bytes)
S_N
0
1
2
3
4
5
6
7
27
28
29
30
2
1
31
SC
Instruction
MISO
0
0
0
0
16 Bit Address
0
0
1
0
13
12
Data Byte 1
4
3
0
S_N
32
33
34
7
6
5
35
36
37
38
39
40
41
42
2
1
0
7
6
5
43
44
45
46
47
2
1
0
SC
Data Byte 2
MISO
4
3
Data Byte 3
4
3
Data Byte n (64 max)
7
6
5
4
3
2
1
0
Example PROG Page Sequence
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
0x01
0x04
0x05
0x06
0x02
0x00
0x80
Dat0
Dat1
…
0x01
0x00
… set REQ bit by writing 0x04 to status register
… -“… read Flash status register until Flash is ready
… set Flash write enable
… write Flash instruction
… Start address, e.g. 80h
… -“… put byte 0 to address
… put byte 1 to address + 1
… max. 64 bytes (page size), then repeat sequence from step 2.
… clear REQ bit by writing 0x00 to status register
… -“-
Revision 1.0, 19-Jun-07
Page 74 of 136
Data Sheet AS8267 / AS8268
Write Enable Sequence
S_N
0
1
2
3
4
5
6
7
SC
MISO
0
0
0
0
0
1
0
1
High Impedance
MOSI
Write Disable Sequence
S_N
0
1
2
3
4
5
6
7
SC
MISO
0
0
MOSI
0
0
0
1
0
0
High Impedance
Read Status Register
Write Status Register
Revision 1.0, 19-Jun-07
Page 75 of 136
Data Sheet AS8267 / AS8268
Page Erase
Instruction
Address
S_N
SC
MISO
0
1
1
2
1
0
3
1
4
1
5
0
6
0
7
0
8
15
9
14
10
13
19
11
12
11
4
20
3
21
2
22
1
23
0
High Impedance
MOSI
Mass Erase
Reset
Serial Input Timing (MOSI)
TCSD
S_N
TCSS
TR
TCSH
TF
TCLD
TCLE
SC
TSU
MISO
THD
MSB In
MOSI
Revision 1.0, 19-Jun-07
LSB In
High Impedance
Page 76 of 136
Data Sheet AS8267 / AS8268
Serial Output Timing (MISO)
S_N
THI
TLO
TCSH
SC
TV
MISO
TDIS
THO
MSB Out
MOSI
LSB Out
Don’t Care
Timing Characteristics
Parameter
Symbol
Min
Max
Unit
S_N Setup Time
T CSS
100
-
ns
S_N Hold Time
T CSH
150
-
ns
S_N Disable Time
T CSD
500
-
ns
Data SetupTime
T SU
30
-
ns
Data Hold Time
T HD
50
-
ns
SC Rise Time
TR
-
2
ns
SC Fall Time
TF
-
2
ns
SC High Time
T HI
150
-
ns
SC Low Time
T LO
150
-
ns
SC Delay Time
T CLD
50
-
ns
SC Enable Time
T CLE
50
-
ns
Output Valid from Clock Low
TV
-
150
ns
Output Hold Time
T HO
0
-
ns
Output Disable Time
T DIS
-
200
ns
Revision 1.0, 19-Jun-07
Note
Page 77 of 136
Data Sheet AS8267 / AS8268
8.6
External EEPROM Requirements
An external EEPROM with SPI bus serial interface is used for non-volatile program and data storage. The SPI
master block that communicates with the EEPROM is specified above. This section explains the requirement
for Serial EEPROMs. It shows the most important figures and tables as a reference. For the details please turn
to the data sheet of your specifically applied EEPROM.
The following minimum requirements must be fulfilled:
Pins
There must be at least the typical SPI pins like
serial data input (EEP_SI), serial data output (EEP_SO)
serial clock input (EEP_SC), chip select input (EEP_S_N)
Clock Rate
The applicable clock rate pin EEP_SC must be ≥ 1MHz.
Status Register
must look like this:
Bit 0 must be the WIP bit, indicating that a write operation is in progress. Only this bit is polled during the
EEPROM upload, means programming of the EEPROM. The Status register can be accessed via the RDSR
instruction.
Data Protection
The write protection block size is given in the table below:
Status Register Bits
BP1
Protected Block
BP0
Array Addresses Protected
Example only
0
0
None
None
0
1
Upper quarter
6000h – 7FFFh
1
0
Upper half
4000h – 7FFFh
1
1
Whole memory
0000h – 7FFFh
Note: The array addresses must be referenced from the data sheet of the specific EEPROM used.
BP1, BP0 allows the selection of one out of 4 protection schemes.
Revision 1.0, 19-Jun-07
Page 78 of 136
Data Sheet AS8267 / AS8268
In order to protect against inadvertent programming the user can see these bits. Please note that the protected
range of EEPROM cannot be overwritten via an SCT command there anymore. Reprogramming must be done
with a dedicated program then.
Instruction Set
Instruction
Name
Instruction Description
Format
READ
03h
Read data from memory starting with selected address
WRITE
02h
Write data to memory beginning at selected address. Most EEPROMs allow page writing
of pages 16, 32, 64 or even more bytes for faster device programming. Before every
page write operation a WREN instruction must be applied – see also bootloading and
uploading sequence for details.
WREN
06h
Write enable EEPROM, enables write operation
RDSR
05h
Read EEPROM Status register
WRDI
08h
Write disable EEPROM, disable write operation
WRSR
01h
Write EEPROM Status register
SPI Modes
These devices can be driven by a microcontroller with its SPI peripheral running in either of the two following
modes:
- CPOL = 0, CPHA = 0
- CPOL = 1, CPHA = 1 (It is recommended to set CPOL = 1, CPHA = 1 in your program: The build-in
bootloader uses this setting as well.)
For these two modes, input data is latched in on the rising edge of Serial Clock (SC), and output data is issued
on the falling edge of Serial Clock (SC).
The recommended mode is shown in Figure 11. The clock polarity SC is ‘1’ when the bus master is in Stand-by
mode and not transferring data (idle state):
- SC remains at 1 for (CPOL = 1, CPHA = 1)
1
1
EEP_SC(in)
EEP_SI(in)
EEP_SO(out )
Figure 11: SPI modes recommended
Revision 1.0, 19-Jun-07
Page 79 of 136
Data Sheet AS8267 / AS8268
Address Roll Over
When the highest address on the EEPROM is reached, e.g. 7FFFh for a 32kB device, then the address counter
must roll over to 0000h.
Unused Upper Address Bits
Unused upper address bits must be ignored in any case. E.g. an 8kB device has a maximum address of 1FFFh
must interpret 7FFFh as 1FFFh, ignoring the higher bits.
Example Pin List
Type
Functionality
Description
EEP_S_N
Pin Name
Input
Chip select, active low
When this input signal is High, the device is deselected and Serial Data
Output (SO) is at high impedance. Unless an internal Write cycle is in
progress, the device will be in the Standby mode. Driving Chip Select
(S_N) Low enables the device, placing it in the active power mode.
EEP_SO
Output
Serial data output
This output signal is used to transfer data serially out of the device. Data
is shifted out on the falling edge of Serial Clock (SC).
EEP_SI
Input
Serial data input
This input signal is used to transfer data serially into the device. It
receives instructions, addresses and the data to be written. Values are
latched on the rising edge of Serial Clock (SC).
EEP_SC
Input
Serial clock
This input signal provides the timing of the serial interface. Instructions,
addresses or data present at Serial Data Input (SI) are latched on the
rising edge of Serial Clock (SC). Data on Serial Data Output (SO)
changes after the falling edge of Serial Clock (SC).
Input
Write protect, active low The main purpose of this input signal is to freeze the size of the area of
memory that is protected against Write instructions (as specified by the
values in the BP1 and BP0 bits of the Status register). This pin must be
driven either High or Low and must be stable during all write operations.
Input
Hold, active low
EEP_WP_N
1)
EEP_HOLD_N
1)
EEP_VCC
Supply Positive supply voltage
EEP_VSS
Supply Negative supply voltage
The Hold (HOLD_N) signal is used to pause any serial communications
with the device without deselecting the device. During the Hold
condition, the Serial Data Output (SO) is high impedance, and Serial
Data Input (SI) and Serial Clock (SC) are Don’t Care. To start the Hold
condition, the device must be selected, with Chip Select (S_N) driven
Low.
Note:
1) No Write Protect (EEP_WP_N) and Hold (EEP_HOLD_N) pins are available on the AS8267 / AS8268 ICs.
These pins must be tied ‘high’ directly at the EEPROM device.
Revision 1.0, 19-Jun-07
Page 80 of 136
Data Sheet AS8267 / AS8268
Instructions Timings
Write Enable (WREN)
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
EEP_SO(out )
Figure 12: Write enable (WREN) sequence
Read Status Register (RDSR)
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
EEP_SO(out )
Figure 13: Read Status register (RDSR) sequence
Read from Memory Array (READ)
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
EEP_SO(out )
Figure 14: Read from memory array (READ) sequence
Revision 1.0, 19-Jun-07
Page 81 of 136
Data Sheet AS8267 / AS8268
Write to Memory Array (WRITE)
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
EEP_SO(out )
Figure 15: Byte write (WRITE) sequence
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
EEP_S_N(in)
EEP_SC(in)
EEP_SI(in)
Figure 16: Page write (WRITE) sequence
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Data Sheet AS8267 / AS8268
8.7
FLASH Memory
The AS8267 / AS8268 provide a 32kByte Flash Memory for program and data. This Flash is organised in 512
pages with 64Bytes each. When the memory is erased all bytes are 0x00.
To speed up writing to the Flash Memory, a page write mode is available. A page program writes the data in the addressed
memory page. It is also possible to write parts of a page or a single byte. Data that has not been addressed
remains unchanged. Before data can be written to the memory, the addressed page or the whole memory must
be erased. A mass erase sets all bit cells in the memory to logic ‘0’. A page erase sets all bit cells of an
addressed page to logic ‘0’.
The Flash memory can be accessed via System Control in UART1 or the SPI_Flash commands.
FLASH Registers
Address
Reset Value
FLASH_STAT
Register Name
9700h
0rra.0000
Note
1)
FLASH_ATTACK
9701h
000s.ssss
1)
Note:
1) rr and s.ssss status bits are copied from Flash memory during boot sequence
‘a‘ is dependent of LOCK bit after reset. If LOCK bit is set then ‘a‘ becomes 0 (access denied) otherwise ‘a‘ becomes 1
and access is granted.
FLASH Status Register
MSB
CPU_PE
Bit
7
6
5
4
LOCK
Symbol
ATK_EN
ACCESS_EN
-
REQ
LSB
WIP
WEL
Function
CPU page erase, triggers a page erase process of the Flash on next CPU write access.
Must be cleared by CPU afterwards (Not to be used by UART1) (read/write)
Locks the Flash memory against unauthorized read access from outside using
LOCK
SET_PW(f7h) or SET_PW1(f8h) command via UART1. Stored in Flash memory (nonvolatile) (read only)
Enables the attack counter using SET_PW1 (f8h) command via UART1. Stored in Flash
ATK_EN
memory (non-volatile) (read only)
ACCESS_EN Grant access to Flash if password entered correctly (read only)
CPU_PE
Not used
3
-
2
REQ
External Flash Request (Not to be used by CPU due to dead lock!) (read/write)
1
WEL
Write enable latch (only writeable by SPI “WREN” command)
0
WIP
Write in progress (read only)
Note:
The WIP bit is set as soon as a Write, Page Erase or Mass Erase command is sent and reset when the Flash is ready again.
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Data Sheet AS8267 / AS8268
FLASH Attack Register
If enabled by the ATK_EN bit in the Flash status register, the attack register logs any unauthorized access to the device and
stores it in the Flash memory. After five attacks the device disables the UART1 interface forever.
MSB
-
-
-
Bit
Symbol
Function
7
-
Not used
6
-
Not used
5
-
Not used
4
A5
5
th
4 attack
2
A3
3
rd
attack
2
nd
attack
1
st
0
A1
A3
A2
LSB
A1
attack
A4
A2
A4
th
3
1
A5
attack
Whenever the password is not entered correctly and the attack counter is enabled one bit of the attack register
is set and its copy is updated in the Flash memory.
Data Organisation in the FLASH Memory
1.
2.
3.
4.
5.
6.
7.
8.
Program data are stored beginning at address 0000h.
Program data size must not be bigger than 32768 – 16 (0000h – 7FEFh).
The length of the program is stored at the two topmost bytes.
For the 32k Flash memory this means: Length (takes 2 bytes) is stored at 7FFE to 7FFFh.
The 8byte password is stored at 7FF0h to 7FF7h.
Non-volatile Flash status flags are located at 7FF8h to 7FF9h.
Meter data and system parameters are stored in the remaining memory space. The allocation of memory space is totally
up to the MCU program.
The program data will not be protected against overwriting processes from the MCU program.
In case there is no program stored in the Flash (boot loader detects all 0s or all 1s at the program length address) the
boot loader forces the MCU to loop on address 0 (“SJMP $”, Hex code: 80FEh).
FLASH Timing
Parameter
Program time
Typ
6.75
Unit
ms
Note
fclk = 3.58MHz
Erase time
3.39
ms
fclk = 3.58MHz
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Data Sheet AS8267 / AS8268
FLASH Memory Reliability
The 32kByte Flash memory implemented in the AS8267 / AS8268 ICs provide an outstanding performance in
respect to data retention time and endurance.
Endurance is the parameter that specifies the cumulative write/erase cycles of the memory cells within the
Flash memory. The data retention time of a Flash memory is a critical end-of-life parameter. This parameter
specifies the maximum period of time, after programming, that data can be expected to be retrieved valid from
the memory.
According to the JEDEC A117 specification the Flash memory has a minimum endurance of 100,000 cycles and
a retention time of 500 years at 65°C.
Data Retention EEPROM austriamicrosystems AG Ea=0.6eV
300
275
250
225
Retention [Years]
200
175
150
125
100
75
50
25
0
75
85
95
105
115
125
135
145
Junction Temperature [°C]
FLASH Security
The AS8267 / AS8268 comprise of two different possibilities to protect Flash content against copying and
manipulation.
The detailed implementation will be explained in this chapter.
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Data Sheet AS8267 / AS8268
General Description
Based on the software development flow it only makes sense to lock the software after the development is
finished. Therefore we can distinguish between access to the Flash during the software development and
access to the Flash after the development is finished.
The protection is implemented in such a way that the external Flash memory access (UART1, SPI via
SPI_Flash) is blocked.
Access during Software Development
During the development phase of the meter software each external access to the Flash must be enabled.
This means that the listed commands are enabled
READ
WRITE Byte
WRITE Page
PAGE ERASE
MASS ERASE
Access after Software Development
After the completion of the software development there are two possible modes of protecting the Flash content.
a) Protection via PASSWORD
If this mode is selected the listed commands are disabled:
READ
WRITE Byte
WRITE Page
PAGE ERASE
MASS ERASE
b) Protection via PASSWORD and ATTACK COUNTER
If this mode is selected the listed commands are disabled and the Attack Counter is enabled:
READ
WRITE Byte
WRITE Page
PAGE ERASE
MASS ERASE
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Data Sheet AS8267 / AS8268
Block Diagram
The block diagram shows the main block involved in the security concept.
According to the block diagram there are four possibilities to get access to the internal Flash memory.
1.
Access via UART1
In this mode program/data can be read from or written in the Flash using commands defined in the SCT
(System Control).
2.
Access via SPI_FLASH Interface
In this mode program/data can be read from or written to the Flash using the SPI_Flash interface. This path
also includes a command interpreter which is able to handle different Flash access commands. Please
refer to the SPI section in this document.
To use this mode the SPI interface must be configured as slave (SPI_Flash).
3.
Access via SPI2 Interface
In this mode it is not possible to directly access the Flash memory from extern due to the missing command
interpreter. A direct access to the Flash therefore would only be possible if there would be a program
available in the mcu doing the command interpretation.
4.
Access via UART2
In this mode there is also no command interpreter in the communication path, so that a direct access to
Flash is not possible.
The Flash memory access via UART1 or SPI_Flash interface is an external Flash memory access and therefore
protected by password.
The Flash memory access via SPI2 interface or UART2 interface is an internal Flash memory and therefore not
protected by password. The protection of this path is up to the user.
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Data Sheet AS8267 / AS8268
Password Protection
If the protection schema “Protection via PASSWORD” is selected the listed commands are disabled:
READ
WRITE Byte
WRITE Page
PAGE ERASE
MASS ERASE
The password is entered via the SET_PW command (instruction code F7h in the UART1 command interpreter)
followed by the 8byte password.
RXD
TXD
0
1
2
3
4
5
6
7
SET_PASSWORD
CMD
D0
D1
8 bytes
D7
0
1
2
3
4
5
6
7
ACK / NACK
Once a password is entered it is encrypted and stored in the Flash memory. At the same time the Flash
memory ‘LOCK’ bit (bit6) is set in Flash status register (9700h). When ‘LOCK’ bit is set the top page of the
Flash memory (storage of program length, password, non-volatile status flags) is blocked for page erase and
write access even when access is granted. This also guarantees that the protection remains even the device is
powered down and powered up again.
Based on the blocked write access of the top page of the Flash memory it is not possible to change an existing
password. A new password can only be assigned after a MASS ERASE.
Once the correct password is entered the listed commands are enabled again.
If the device memory is blank (e.g. after FAB-out) the access to the Flash memory is open and no password is
required.
Password + Attack Counter Protection
If the protection schema “Protection via PASSWORD and ATTACK COUNTER” is selected the listed commands
are disabled:
READ
WRITE Byte
WRITE Page
PAGE ERASE
MASS ERASE
The password is entered in this case via the SET_PW1 command (instruction code F8h in the UART1 command
interpreter) followed by the 8byte password.
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Data Sheet AS8267 / AS8268
RXD
TXD
0
1
2
3
4
5
6
7
SET_PASSWORD
CMD
D0
D1
8 bytes
D7
0
1
2
3
4
5
6
7
ACK / NACK
In this mode the ATK_EN bit (bit5) is enabled in the Flash status register (9700h), and the attack register logs
any unauthorized access to the device and stores it in the Flash memory. Also in this mode once a password is
entered it is encrypted and stored in the Flash memory. At the same time the Flash memory ‘LOCK’ bit (bit6) is
set in Flash status register. When ‘LOCK’ bit is set the top page of the Flash memory (storage of program
length, password, non-volatile status flags) is blocked for page erase and write access even when access is
granted. This also guarantees that the protection remains even the device is powered down and powered up
again.
Based on the blocked write access of the top page of the Flash memory it is not possible to change an existing
password. A new password can only be assigned after a MASS ERASE.
Once the correct password is entered the listed commands are enabled again.
In case an incorrect password is entered the Attack Counter is increased. After five attacks the UART1 will be
disabled by switching off the internal clock for the UART1.
In this state the device is locked forever.
If the device memory is blank (e.g. after FAB-out) the access to the Flash memory is open and no password is
required.
To give the user the possibility of reusing a blocked device he has to implement special functionality in his
software.
The following example describes a possible implementation.
Monitoring of one of the non blocked interfaces (SPI2 or UART2) within the customer specific MCU
software
If a specific (defined by the developer) sequence is applied the MCU can perform a page erase of the
up most page (holds also program length) in the Flash memory.
After a reset the device will now start with its default parameters and will not perform an automatic
program load via the boot loader.
In this operating mode it is than possible to write the program length again into the Flash memory. Also
a new password can be entered.
After a reset the meter will work again and also stored metering data can be accessed.
MCU Access to the FLASH Memory
The listed commands are available for the MCU access.
READ
WRITE Byte
PAGE ERASE
Initiation of a PAGE ERASE by the MCU the CPU_PE bit in the FLASH Status Register (9700h) has to be set.
After this a WRITE command with the selected address has to be performed.
After completion of the page erase procedure the CPU_PE bit has to be cleared by the MCU.
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Data Sheet AS8267 / AS8268
8.8
8051 Microcontroller (MCU)
The MCU is a derivative of the well-known 8051 microcontroller. The MCU block consists of an 8051
compatible microprocessor core, Flash memory, data memory (X_RAM), squareroot calculation unit and two
UARTs for debugging and communication purposes. The Special Function Registers (SFR) section enfolds the
standard blocks like the 16 bit timer (Timer 0), 128 bytes of internal data memory (I_RAM) and a serial
interface (UART1). Furthermore, a squareroot block and a second serial interface (UART2) are also provided.
Timer 1, Port 0 to 3 and the UART are not implemented exactly the same as in the original 8051. Instead, the
bus extension (Port 0, 2 on single chip 8051) provides access to on-chip periphery, which comprises a serial
peripheral interface (SPI), a real time clock (RTC), nine general purpose I/Os (MPIO), the LCD driver (LCDD),
the DSP block that interfaces to the analog front end and system control registers (SCT). The MCU block is
configured as Von Neumann architecture with the program in the Flash memory staring from 0000h and the
data memory (X_RAM) and periphery section starting from 8000h up to FFFFh. All 64kB of memory can be
accessed with both, the MOVC instruction (for program fetches and data read) and the MOVX instruction (for
data read/store). The interrupt controller enfolds 7 internal interrupt sources, for having all necessary
peripherals already on chip.
Internal
Interrupt Sources
Interrupt
Control
Optional
Serial
EEPROM
LC
Display
SPI
M/S
LCDD
MCU
128 bytes
I_RAM
Timer 0
32kB
FLASH
RTC
Temperature
Sensor
CPU
Clock
Divider
Mclk
SQRT
UART2
rxd2
1kB
X_RAM
UART1
SCT
MPIO
DSP
AFE
txd2
RXD
TXD
I/Os
Figure 17: MCU block diagram
Legend
CPU ................ 8051 compatible microcontroller core
I_RAM ............. 128 bytes static RAM, range 00h to 7Fh of 8051
X_RAM ............ 1024 bytes static RAM, (extended) memory for data storage
FLASH ............ 32kB Flash memory, primarily for program storage, maybe used also for data
Timer 0............ 16 bit timer (due to 8051 standard)
UART1 ............ serial interface RS232 (due to 8051 standard) with extended baudrate generator
UART2 ............ serial interface RS232 with extended baudrate generator
SQRT .............. square root calculation out of 5 bytes (40 bits) input, 2.5 bytes (20 bits) output
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Data Sheet AS8267 / AS8268
SPI.................. serial peripheral interface, used to access an external EEPROM
LCDD .............. LCD driver block
RTC ................ real time clock, time/data may be set via UART1 (SCT)
MPIO............... multi-purpose I/O pins, configurable inputs and outputs
DSP ................ digital signal processing unit interfaces to analog front end (AFE)
AFE................. analog front end, includes amplifiers and A to D converters
SCT ................ system control unit, combined with UART1 used for debugging/programming of the device
Key Features
-
8051 compatible 8 bit oriented microcontroller core
128 bytes of internal data memory (I_RAM)
32kB Flash memory
1kB data memory (X_RAM)
Von Neumann architecture, shared program and data memory
Cycle optimized compared to standard 8051, some instructions are executed in a single clock cycle
128 bytes of SFR range
Standard SFRs: Timer 0, UART1 (with 16 baudrate reg.)
Specific SFRs: UART2 (with 16 bit baudrate reg.), SQRT block
Fully compatible 8051 instruction set including DA, MUL and DIV instruction
7 internal interrupt sources
Ports P0, P1, P2, P3 are not implemented
P0 and P2 are accessible as registers
Register PCON is not implemented
No idle mode via PCON
Automatic bootload of application program after power-on reset
6 clock cycles per instruction (12 cycles in standard 8051)
1 data pointer DPTR
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Data Sheet AS8267 / AS8268
Instruction Set
The instruction set is fully compatible to the 8051 standard. This allows the use of commonly available software
development tools for A51 Assembler, C-Compiler and code simulators. The instructions marked with the note
2)
are cycle optimised and execute in a single cycle compared to two cycles in standard 8051 controllers.
Hex
Code
Mnemonic
Operands
B/C
1)
Hex
Code
Mnemonic
Operands
B/C
1)
00
NOP
1/1
30
JNB
bit addr, code addr
01
AJMP
code addr
2/2
31
ACALL
code addr
3/2
02
LJMP
code addr
3/2
32
RETI
03
RR
A
1/1
33
RLC
A
1/1
04
INC
A
1/1
34
ADDC
A, #data
2/1
05
INC
dir
2/1
35
ADDC
A, dir
2/1
06
INC
@R0
1/1
36
ADDC
A, @R0
1/1
07
INC
@R1
1/1
37
ADDC
A, @R1
1/1
08
INC
R0
1/1
38
ADDC
A, R0
1/1
09
INC
R1
1/1
39
ADDC
A, R1
1/1
0A
INC
R2
1/1
3A
ADDC
A, R2
1/1
2/2
1/2
0B
INC
R3
1/1
3B
ADDC
A, R3
1/1
0C
INC
R4
1/1
3C
ADDC
A, R4
1/1
0D
INC
R5
1/1
3D
ADDC
A, R5
1/1
0E
INC
R6
1/1
3E
ADDC
A, R6
1/1
0F
INC
R7
1/1
3F
ADDC
A, R7
1/1
10
JBC
bit addr, code
3/2
40
JC
code addr
2/2
11
ACALL
code addr
2/2
41
AJMP
code addr
2/2
12
LCALL
code addr
3/2
42
ORL
dir, A
2/1
13
RRC
A
1/1
43
ORL
dir, #data
3/2
2/1
14
DEC
A
1/1
44
ORL
A, #data
15
DEC
dir
2/1
45
ORL
A, dir
2/1
16
DEC
@R0
1/1
46
ORL
A, @R0
1/1
17
DEC
@R1
1/1
47
ORL
A, @R1
1/1
18
DEC
R0
1/1
48
ORL
A, R0
1/1
19
DEC
R1
1/1
49
ORL
A, R1
1/1
1A
DEC
R2
1/1
4A
ORL
A, R2
1/1
1B
DEC
R3
1/1
4B
ORL
A, R3
1/1
1C
DEC
R4
1/1
4C
ORL
A, R4
1/1
1D
DEC
R5
1/1
4D
ORL
A, R5
1/1
1E
DEC
R6
1/1
4E
ORL
A, R6
1/1
1F
DEC
R7
1/1
4F
ORL
A, R7
1/1
20
JB
bit addr, code
3/2
50
JNC
code addr
2/2
21
AJMP
code addr
2/2
51
ACALL
code addr
2/2
22
RET
1/2
52
ANL
dir, A
2/1
23
RL
1/1
53
ANL
dir, #data
3/2
24
ADD
A, #data
1/1
54
ANL
A, #data
2/1
25
ADD
A, dir
2/1
55
ANL
A, dir
2/1
26
ADD
A, @R0
2/1
56
ANL
A, @R0
1/1
27
ADD
A, @R1
1/1
57
ANL
A, @R1
1/1
28
ADD
A, R0
1/1
58
ANL
A, R0
1/1
29
ADD
A, R1
1/1
59
ANL
A, R1
1/1
2A
ADD
A, R2
1/1
5A
ANL
A, R2
1/1
2B
ADD
A, R3
1/1
5B
ANL
A, R3
1/1
2C
ADD
A, R4
1/1
5C
ANL
A, R4
1/1
2D
ADD
A, R5
1/1
5D
ANL
A, R5
1/1
2E
ADD
A, R6
1/1
5E
ANL
A, R6
1/1
2F
ADD
A, R7
1/1
5F
ANL
A, R7
1/1
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A
Page 92 of 136
Data Sheet AS8267 / AS8268
Hex
Code
Mnemonic
Operands
B/C
1)
Hex
Code
Mnemonic
code addr
2/2
90
MOV
Operands
B/C
1)
60
JZ
DPTR, #data
3/2
61
AJMP
code addr
2/2
91
ACALL
code addr
62
XRL
dir, A
2/1
92
MOV
bit addr, C
63
XRL
dir, #data
3/2
93
MOVC
A, @A+DPTR
2/2
64
XRL
A, #data
2/1
94
SUBB
A, #data
2/1
65
XRL
A, dir
2/1
95
SUBB
A, dir
2/1
66
XRL
A, @R0
1/1
96
SUBB
A, @R0
1/1
67
XRL
A, @R1
1/1
97
SUBB
A, @R1
1/1
68
XRL
A, R0
1/1
98
SUBB
A, R0
1/1
69
XRL
A, R1
1/1
99
SUBB
A, R1
1/1
6A
XRL
A, R2
1/1
9A
SUBB
A, R2
1/1
6B
XRL
A, R3
1/1
9B
SUBB
A, R3
1/1
6C
XRL
A, R4
1/1
9C
SUBB
A, R4
1/1
6D
XRL
A, R5
1/1
9D
SUBB
A, R5
1/1
6E
XRL
A, R6
1/1
9E
SUBB
A, R6
1/1
6F
XRL
A, R7
1/1
9F
SUBB
A, R7
1/1
70
JNZ
code addr
2/2
A0
ORL
C, /bit addr
71
ACALL
code addr
2/2
A1
AJMP
code addr
72
ORL
C, bit addr
2/1 2 )
A2
MOV
C, bit addr
73
JMP
@A+DPTR
1/2
A3
INC
DPTR
74
MOV
A, #data
2/1
A4
MUL
AB
75
MOV
dir, #data
2/1
A5
n/a
(reserved)
76
MOV
@R0, #data
1/1
A6
MOV
@R0, dir
2/1 2 )
77
MOV
@R1, #data
1/1
A7
MOV
@R1, dir
2/1 2 )
78
MOV
R0, #data
1/1
A8
MOV
R0, dir
2/1 2 )
79
MOV
R1, #data
1/1
A9
MOV
R1, dir
2/1 2 )
7A
MOV
R2, #data
1/1
AA
MOV
R2, dir
2/1 2 )
2/2
2/1
2)
2/1 2 )
2/2
2/1
1/1 2 )
1/4
1/1
7B
MOV
R3, #data
1/1
AB
MOV
R3, dir
2/1
2)
7C
MOV
R4, #data
1/1
AC
MOV
R4, dir
2/1
2)
7D
MOV
R5, #data
1/1
AD
MOV
R5, dir
2/1
2)
7E
MOV
R6, #data
1/1
AE
MOV
R6, dir
2/1
2)
7F
MOV
R7, #data
1/1
AF
MOV
R7, dir
2/1
2)
80
SJMP
code addr
2/2
B0
ANL
C, /bit addr
2/1 2 )
81
AJMP
code addr
2/2
B1
ACALL
code addr
2/2
82
ANL
C, bit addr
2/1 2 )
B2
CPL
bit addr
2/1
83
MOVC
A, @A+PC
2/2
B3
CPL
C
1/1
84
DIV
AB
1/4
B4
CJNE
A, #data, code
3/2
85
MOV
dir, dir
3/2
B5
CJNE
A, dir, code
3/2
86
MOV
dir, @R0
2/1
2)
B6
CJNE
@R0, #data, code
3/2
87
MOV
dir, @R1
2/1
2)
B7
CJNE
@R1, #data, code
3/2
88
MOV
dir, R0
2/1
2)
B8
CJNE
R0, #data, code
3/2
89
MOV
dir, R1
2/1
2)
B9
CJNE
R1, #data, code
3/2
8A
MOV
dir, R2
2/1
2)
BA
CJNE
R2, #data, code
3/2
8B
MOV
dir, R3
2/1
2)
BB
CJNE
R3, #data, code
3/2
8C
MOV
dir, R4
2/1 2 )
BC
CJNE
R4, #data, code
3/2
8D
MOV
dir, R5
2/1 2 )
BD
CJNE
R5, #data, code
3/2
8E
MOV
dir, R6
2/1 2 )
BE
CJNE
R6, #data, code
3/2
8F
MOV
dir, R7
2/1 2 )
BF
CJNE
R7, #data, code
3/2
Revision 1.0, 19-Jun-07
Page 93 of 136
Data Sheet AS8267 / AS8268
Hex
Code
Mnemonic
Operands
B/C
1)
dir
2/1
2)
Hex
Code
E0
Mnemonic
Operands
B/C
1)
C0
PUSH
MOVX
A, @DPTR
2/2
C1
AJMP
code addr
2/2
E1
C2
CLR
bit addr
2/1
E2
AJMP
code addr
2/2
MOVX
A, @R0
C3
CLR
C
1/1
E3
MOVX
2/2
A, @R1
2/2
1/1
C4
SWAP
A
1/1
E4
CLR
A
C5
XCH
A, dir
2/1
E5
MOV
A, dir
2/1
C6
XCH
A, @R0
1/1
E6
MOV
A, @R0
1/1
C7
XCH
A, @R1
1/1
E7
MOV
A, @R1
1/1
C8
XCH
A, R0
1/1
E8
MOV
A, R0
1/1
C9
XCH
A, R1
1/1
E9
MOV
A, R1
1/1
CA
XCH
A, R2
1/1
EA
MOV
A, R2
1/1
CB
XCH
A, R3
1/1
EB
MOV
A, R3
1/1
CC
XCH
A, R4
1/1
EC
MOV
A, R4
1/1
CD
XCH
A, R5
1/1
ED
MOV
A, R5
1/1
CE
XCH
A, R6
1/1
EE
MOV
A, R6
1/1
CF
XCH
A, R7
D0
POP
dir
D1
ACALL
D2
SETB
1/1
EF
MOV
A, R7
1/1
2/1 2 )
F0
MOVX
@DPTR, A
1/2
code addr
2/2
F1
ACALL
code addr
2/2
bit addr
2/1
F2
MOVX
@R0, A
1/2
D3
SETB
C
1/1
F3
MOVX
@R1, A
1/2
D4
DA
A
1/1
F4
CPL
A
1/1
D5
DJNZ
dir, code addr
3/2
F5
MOV
dir, A
2/1
D6
XCHD
A, @R0
1/1
F6
MOV
@R0, A
1/1
D7
XCHD
A, @R1
1/1
F7
MOV
@R1, A
1/1
D8
DJNZ
R0, code addr
2/2
F8
MOV
R0, A
1/1
D9
DJNZ
R1, code addr
2/2
F9
MOV
R1, A
1/1
DA
DJNZ
R2, code addr
2/2
FA
MOV
R2, A
1/1
DB
DJNZ
R3, code addr
2/2
FB
MOV
R3, A
1/1
DC
DJNZ
R4, code addr
2/2
FC
MOV
R4, A
1/1
DD
DJNZ
R5, code addr
2/2
FD
MOV
R5, A
1/1
DE
DJNZ
R6, code addr
2/2
FE
MOV
R6, A
1/1
DF
DJNZ
R7, code addr
2/2
FF
MOV
R7, A
1/1
dir .............. variable in I_RAM
code addr ... address in code memory
data ........... immediate data
bit addr....... address of a bit in bit-addressable I_RAM
Notes:
1) ‘B’ = number of bytes
‘C’ = number of cycles
2) Optimised execution in a single cycle; normally 2 cycles
Revision 1.0, 19-Jun-07
Page 94 of 136
Data Sheet AS8267 / AS8268
Addressing Modes
The MCU comprises all standard 8051 addressing modes. For completeness they are listed here. There are
five types. In two byte instructions the destination is specified first, then the source.
Mode
Examples
Notes
Register addressing
MOV A, R0
Register R0 in I_RAM one out of 4 banks
selected
Direct addressing
MOV R0, A
Moves contents of A to R0
Register indirect addressing
MOV @R0, A
MOVX @DPTR, A
Moves contents of A to location addressed
by R0, or by DPTR
Immediate addressing
MOV R0, #data
Moves immediate #data to R0
Index addressing
MOVC A, @A+DPTR
MOVC A, @A+PC
Moves contents of location addressed by
A+DPTR, or A+PC to A. For reading lookup
tables, applies to program memory only
Interrupt Controller
The 8051 core provides 7 interrupt sources: 2 of them are the same as in the standard 8051, the others are
tied to specific internal sources. Each interrupt causes the program to jump to the corresponding interrupt
vector if the interrupt is enabled in the interrupt enable register (IE). The interrupt priority can be controlled via
the interrupt priority register (IP) in order to override the predefined priority, starting with IP.0 as highest. For
further information on the interrupt sources refer to the appropriate chapters.
Interrupt Enable Register (IE)
Each of the interrupt sources can be individually enabled or disabled by setting the corresponding bit in the IE
register. This register contains a global enable bit EA. By clearing this bit all interrupts can be disabled at
once.
IE
MSB
EA
LSB
ERTC
ES2
ES
ESPI
EIOX
ET0
EDSP
PS
PSPI
PIOX
PT0
PDSP
Enable bit = 0 disables the interrupt
Enable bit = 1 enables the interrupt
Interrupt Priority Register (IP)
IP
MSB
-
LSB
PRTC
PS2
Priority bit = 1 assigns high priority
Priority bit = 0 assigns low priority
Revision 1.0, 19-Jun-07
Page 95 of 136
Data Sheet AS8267 / AS8268
Interrupt
Source
RTC
UART2
UART1
SPI
MPIO
Timer 0
DSP
Interrupt
Vector
0033h
002Bh
0023h
001Bh
0013h
000Bh
0003h
Note:
Timer0 must have the highest priority in the IP register. No other interrupt should be assigned with a high priority.
Symbol
EA
Position
1
IE.7
ERTC
ES2
ES
ESPI
EIOX
ET0
EDSP
IE.6
IE.5
IE.4 1
IE.3
IE.2
1
IE.1
IE.0
Function
Disables all interrupt when 0. If EA = 1 each interrupt is
individually enabled due to its enable bit.
RTC real time clock, interrupt enable bit
UART2, serial port, interrupt enable bit
UART1, serial port, interrupt enable bit
SPI serial port, interrupt enable bit
MPIO external pin, interrupt enable bit
Timer 0, interrupt enable bit
DSP data available
Priority
Lowest
Highest
Note:
1)
Standard 8051 bits
Interrupt Priorities
Each interrupt source can be individually assigned one of two priority levels. A low priority interrupt can always
be interrupted by a higher-priority interrupt, but not by another low priority interrupt. A high-priority interrupt
cannot be interrupted by any other interrupt source.
If the corresponding IP bit is set then this interrupt is serviced first if another interrupt request occurs at the
same time where the IP bit is zero.
Interrupt on the same priority level are serviced due to the internal polling sequence starting with DSP highest
down to RTC lowest.
Symbol
PRTC
PS2
PS
PSPI
PIOX
PT0
PDSP
Position
IP.7
IP.6
IP.5
1
IP.4
IP.3
IP.2
1
IP.1
IP.0
Function
Real time clock, priority bit
UART2 serial port, priority bit
UART1 serial port, priority bit
SPI serial port, priority bit
MPIO external pin, priority bit
Timer 0, priority bit
DSP priority bit
Source Flags
TSA, STF, A1F, A2F
RI, TI
RI, TI
ITRA
in Status 0 / Status 1
TF0
dai, alarm
Note:
1)
Standard 8051 bits
Revision 1.0, 19-Jun-07
Page 96 of 136
Data Sheet AS8267 / AS8268
Source
IE Register
IP Register
IP = 1
PDSP
Priority Level
High
IP = 0
High
Priority
Interrupt
PTO
Priority
Level
Low
PIOX
PSPI
Polling
Sequence
PS
PS2
PRTC
Global enable
Individual enables
Low
Priority
Interrupt
Figure 18: Interrupt control system
Revision 1.0, 19-Jun-07
Page 97 of 136
Data Sheet AS8267 / AS8268
Memory Maps
The 8051 MCU is configured as Von Neumann architecture merging program and data range into one 64kB
address space. This space is completely accessible via MOVX and partly accessible via MOVC (0000h –
5FFFh). Besides, there is the typical 8051 structure with 128 bytes of internal memory (I_RAM) and the special
function registers (SFRs) also in a 128 byte address space.
XDATA
Memory
SFRs
FFh
FFFFh
Special
Function
Registers
unused
9FFFh
C000h
80h
unused
unused
Direct addressing
A000h
9000h
8000h
Internal Memory
1kB X_RAM
7FFFh
7Fh
MPIO
SPI
DSP
LCDD
RTC
SCT
32kB
FLASH
128 bytes
I_RAM
00h
9500h
9400h
9300h
9200h
9100h
9000h
0000h
Direct addressing
Register indirect
addressing
Register addressing
(4 banks)
MOVX A, @DPTR
MOVX @DPTR, A
Bit addressing
MOVC A, @A+PC
MOVC A, @A+DPTR
}
only for 0000h – 7FFFh
MOVX @Ri, A
MOVXA, @Ri with Ri ε {R0, R1},
P2 represents upper address bits
FLASH Memory
The Flash memory shares address and output data lines with the X_RAM. 32kB out of 64kB addressable
memory are used: 0000h – 7FFFh for program data storage.
Revision 1.0, 19-Jun-07
Page 98 of 136
Data Sheet AS8267 / AS8268
Data Memory (X_RAM) and Block Interfaces
The following table shows the start (and stop) addresses for the X_RAM and the block interfaces.
These locations can be accessed with the MOVX instruction.
Start
Address
Stop
Address
Contents
8000h
83FFh
X_RAM
9000h
9007h
SCT
9100h
9134h
RTC
9180h
9184h
WDT
9200h
9220h
LCDD
9300h
9338h
DSPREG (MDR/SREG)
9400h
9403h
EEP_SPI
9500h
951Fh
MPIO
9600h
9604h
TEMPSENS
9700h
9701h
FLASH (STAT/ATTACK)
Detailed Memory map:
Address Contents
8000h
…
Address Contents
83FFh
X_RAM
Address Contents
Address Contents
X_RAM
9000h
-
9001h
enable signals
9002h
clkdiv[2:0]
9003h
-
9100h
Seconds/VL
9101h
Minutes
9102h
Hours
9103h
Days
9104h
Weekdays
9105h
Months/Cent.
9106h
Years
9107h
-
9108h
-
9109h
-
910Ah
-
910Bh
-
910Ch
-
910Dh
-
910Eh
-
910Fh
-
9110h
Cont./Status1
9111h
Cont./Status2
9112h
Sec.Tim.B 0
9113h
Sec.Tim.B 1
9114h
Min.Alarm 1
9115h
Hour Alarm 1
9116h
Day Alarm 1
9117h
Mon. Alarm 1
9118h
YearsAlarm 1
9119h
Min.Alarm 2
911Ah
Hour Alarm 2
911Bh
Day Alarm 2
911Ch
Mon. Alarm 2
911Dh
YearsAlarm 2
911Eh
-
911Fh
-
9130h
DivReg B 0
9131h
DivReg B 1
9132h
DivReg B 2
9133h
Freq. Trim
9180h
WDTE
9181h
WDTCLK
9200h
reg1[7:0]
9201h
reg1[15:8]
9202h
reg1[23:16]
9203h
reg1[31:24]
9204h
reg1[39:32]
9205h
reg1[47:40]
9206h
reg1[55:48]
9207h
reg1[63:56]
9208h
reg1[71:64]
9209h
reg1[79:72]
920Ah
reg1[87:80]
920Bh
reg1[95:88]
920Ch
-
920Dh
-
920Eh
-
920Fh
-
9210h
reg2[7:0]
9211h
reg2[15:8]
9212h
reg2[23:16]
9213h
reg2[31:24]
9214h
reg2[39:32]
9215h
reg2[47:40]
9216h
reg2[55:48]
9217h
reg2[63:56]
9218h
reg2[71:64]
9219h
reg2[79:72]
921Ah
reg2[87:80]
921Bh
reg2[95:88]
921Ch
-
921Dh
-
921Eh
use_reg
921Fh
selvlcd[2:0]
Revision 1.0, 19-Jun-07
SCT
RTC
WDT
LCDD
Page 99 of 136
Data Sheet AS8267 / AS8268
Address Contents
Address Contents
Address Contents
Address Contents
9220h
lcdd_pd
9300h
samptoend 0
9301h
samptoend 1
9302h
np[7:0]
9303h
np[15:8]
9304h
np[23:16]
9305h
np[31:24]
9306h
sos_v[7:0]
9307h
sos_v[15:8]
9308h
sos_v[23:16]
9309h
sos_v[31:24]
930Ah
sos_v[35:32]
930Bh
sos_i1[7:0]
930Ch
sos_i1[15:8]
930Dh
sos_i1[23:16]
930Eh
sos_i1[31:24]
930Fh
sos_i1[39:32]
9310h
sos_i1[47:40]
9311h
sos_i1[53:48]
9312h
sos_i2[7:0]
9313h
sos_i2[15:8]
9314h
sos_i2[23:16]
9315h
sos_i2[31:24]
9316h
sos_i2[39:32]
9317h
sos_i2[47:40]
9318h
sos_i2[53:48]
9319h
-
931Ah
-
931Bh
-
931Ch
-
931Dh
-
931Eh
-
931Fh
-
9320h
pcorr_i1[7:0]
9321h
pcorr_i1[8]
9322h
pcorr_i2[7:0]
9323h
pcorr_i2[8]
9324h
cal_v[7:0]
9325h
cal_v[15:8]
9326h
cal_i1[7:0]
9327h
cal_i1[15:8]
9328h
cal_i2[7:0]
9329h
cal_i2[15:8]
932Ah
pulselev_i1 0
932Bh
pulselev_i1 1
932Ch
pulselev_i1 2
932Dh
pulselev_i2 0
932Eh
pulselev_i2 1
932Fh
pulselev_i2 2
9330h
mconst[3:0]
9331h
-
9332h
nsamp[7:0]
9333h
nsamp[15:8]
9334h
vconst[7:0]
9335h
vconst[13:8]
9336h
Select
9337h
Gains
9338h
Status
9339h
-
933Ah
-
933Bh
-
9400h
SSPCON
9401h
SSPCLKDIV
9402h
SSPSTAT
9403h
SSPBUF
9500h
make_irq0
9501h
make_irq1
9502h
out_mux0
9503h
out_mux1
9504h
out_mux2
9505h
set_en0
9506h
set_en1
9507h
sel_drv0
9508h
sel_drv1
9509h
sel_pupd0
950Ah
sel_pupd1
950Bh
sel_in
950Ch
sel_refp
950Dh
in0
950Eh
in1
950Fh
out0
9510h
out1
9511h
out2
9512h
out3
9513h
out4
9514h
out5
9515h
out6
9516h
out7
9517h
out8
9518h
out9
9519h
out10
951Ah
out11
951Bh
pcnt0
951Ch
pcnt1
951Dh
pcnt2
951Eh
Status0
951Fh
Status1
9600h
TS_Status
9601h
TS_Result0
9602h
TS_Result1
9603h
TS_OffsetCorr0
9604h
TS_OffsetCorr1
9700h
FLASH_STAT
9701h
FLASH_ATTACK
9702h
-
9703h
-
Revision 1.0, 19-Jun-07
DSP
SPI2
MPIO
TS
FLASH
Page 100 of 136
Data Sheet AS8267 / AS8268
Internal Memory (I_RAM)
128 bytes of I_RAM are provided, which can be accessed via 3 address modes.
- All memory 00h to 7Fh is directly addressable.
- 00h to 1Fh are register addressable in four banks. Bank switching is done in PSW (Program Status Word).
- 20h to 2Fh are bit addressable, which means that each bit of these registers can be set/cleared separately.
I_RAM Locations
78h
79h
7Ah
7Bh
7Ch
7Dh
7Eh
70h
71h
72h
73h
74h
75h
76h
7Fh
77h
68h
69h
6Ah
6Bh
6Ch
6Dh
6Eh
6Fh
60h
61h
62h
63h
64h
65h
66h
67h
58h
59h
5Ah
5Bh
5Ch
5Dh
5Eh
5Fh
50h
51h
52h
53h
54h
55h
56h
57h
48h
49h
4Ah
4Bh
4Ch
4Dh
4Eh
4Fh
40h
41h
42h
43h
44h
45h
46h
47h
38h
39h
3Ah
3Bh
3Ch
3Dh
3Eh
3Fh
30h
31h
32h
33h
34h
35h
36h
37h
28h bit 40-47
29h bit 48-4F
2Ah bit 50-57
2Bh bit 58-5F
2Ch bit 60-67
2Dh bit 68-6F
2Eh bit 70-77
2Fh bit 78-7F
20h bit 00-07
21h bit 08-0F
22h bit 10-17
23h bit 18-1F
24h bit 20-27
25h bit 28-2F
26h bit 30-37
27h bit 38-3F
18h R0
19h R1
1Ah R2
1Bh R3
1Ch R4
1Dh R5
1Eh R6
1Fh R7
10h R0
11h R1
12h R2
13h R3
14h R4
15h R5
16h R6
17h R7
08h R0
09h R1
0Ah R2
0Bh R3
0Ch R4
0Dh R5
0Eh R6
0Fh R7
00h R0
01h R1
02h R2
03h R3
04h R4
05h R5
06h R6
07h R7
The first 4 x 8 bytes of the internal memory can be addressed via instructions using the register addressing
mode (register bank 0, 1, 2, 3). The following 16 bytes (16 x 8 = 128 bits, address 20h to 2Fh) can be
addressed via instructions using the direct-bit addressing mode. The address space from 30h to 7Fh is
accessible via the direct addressing mode only. Gray-shaded R0 and R1 registers can be used for register
indirect addressing.
Special Function Registers (SFR)
The following table shows the locations of the Special Function Registers. SFRs in bold style are original 8051
registers. SFRs in italic style are additional registers specific to the AS8267 / AS8268 ICs.
Revision 1.0, 19-Jun-07
Page 101 of 136
Data Sheet AS8267 / AS8268
SFR Locations
F8h
F9h
FAh
FBh
FCh
FDh
FEh
F0h B
F1h
F2h
F3h
F4h
F5h
F6h
FFh
F7h
E8h SQRTIN0
E9h SQRTIN1
EAh SQRTIN2
EBh SQRTIN3
ECh SQRTIN4
EDh SQRTOUT0
EEh SQRTOUT1
EFh SQRTOUT2
E0h ACC
E1h
E2h
E3h
E4h
E5h
E6h
E7h
D8h
D9h
DAh
DBh
DCh
DDh
DEh
DFh
D0h PSW
D1h
D2h
D3h
D4h
D5h
D6h
D7h
C8h
C9h
CAh
CBh
CCh
CDh
CEh
CFh
C0h SCON2
C1h SBUF2
C2h SBAUDL2
C3h SBAUDH2
C4h
C5h
C6h
C7h
B8h IP
B9h
BAh
BBh
BCh
BDh
BEh
BFh
B0h SOVR2
B1h
B2h
B3h
B4h
B5h
B6h
B7h
A8h IE
A9h
AAh
ABh
ACh
ADh
AEh
AFh
A0h P2
A1h
A2h
A3h
A4h
A5h
A6h
A7h
98h SCON
99h SBUF
9Ah SBAUDL
9Bh SBAUDH
9Ch
9Dh
9Eh
9Fh
90h SOVR
91h
92h
93h
94h
95h
96h
97h
88h TCON
89h TMOD
8Ah TL0
8Bh
8Ch TH0
8Dh
8Eh T0PRE
8Fh
80h P0
81h SP
82h DPL
83h DPH
84h
85h
86h
87h
128 bytes of SFR address space is available using the direct addressing mode. The following table describes
the use of the register bytes:
Symbol
Register Name
Address Notes
Standard Registers
ACC
Accumulator
E0h
B
B Register
F0h
PSW
Program Status Word
D0h
SP
Stack Pointer
81h
DPTR
Data Pointer 2 Bytes
DPL
Low Byte
82h
DPH
High Byte
83h
P0
Port 0
80h
P2
Port 2
A0h
IP
Interrupt Priority Control
B8h
IE
Interrupt Enable Control
A8h
TMOD
Timer Mode Control
89h
TCON
Timer Control
88h
TH0
Timer 0 High Byte
8Ch
TL0
Timer 0 Low Byte
8Ah
SCON
Serial Control (UART1)
98h
SBUF
Serial Data Buffer (UART1)
99h
Custom Registers
T0PRE
Timer 0 Prescaler
SOVR
Serial Overflow (UART1)
90h
SBaudL
Serial Baudrate Low (UART1)
9Ah
SBaudH
Serial Baudrate High (UART1)
9Bh
SCON2
UART2 Control
C0h
SBUF2
UART2 Serial Data Buffer
C1h
Revision 1.0, 19-Jun-07
8Eh
Page 102 of 136
Data Sheet AS8267 / AS8268
Symbol
Register Name
SBaudL2
UART2 Baudrate Low
Address Notes
C2h
SBaudH2
UART2 Baudrate High
C3h
SOVR2
UART2 Overflow
B0h
SQRTIN0
Square Root Input [7:0]
E8h
SQRTIN1
Square Root Input [15:8]
E9h
SQRTIN2
Square Root Input [23:16]
EAh
SQRTIN3
Square Root Input [31:24]
EBh
SQRTIN4
Square Root Input [39:32]
Writing to this location triggers the
squareroot calculation
ECh
SQRTOUT0 Square Root Output [7:0]
EDh
SQRTOUT1 Square Root Output [15:8]
EEh
SQRTOUT2 Square Root Output [23:16]
EFh
Notes:
1) Ports P1 and P3 do not exist.
2) Timer 1 is not implemented (and the related SFRs).
3) Ports P0 and P2 are not connected to pins.
P0 and P2 can be used as a register in general.
However, P2 can be used for X_RAM access, when ‘@Ri’ is used in the register indirect addressing mode
(with Ri being either R0 or R1). In that case P2 will form the higher byte of the X_RAM address.
4) IE/IP: The sources for the interrupts are defined in interrupt controller section.
5) TCON, TMOD, TH0, TLO described in section Timer 0.
6) SCON, SBUF, SBaudL, SBaudH, SOVR are related to UART1 described in the UART section.
7) SCON2, SBUF2, SBaudL2, SBaudH2, SOVR2 are related to UART2 described in the UART2 section.
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Data Sheet AS8267 / AS8268
Squareroot Block (SQRT)
This SQRT block calculates the square root of a 40 bit input value (mapped to 5 eight bit input registers).
The output is a 20 bit number which is mapped to 3 eight bit output registers.
The calculation starts immediately after the least significant byte has been written (= address E8h).
For the square root calculation the Gypsi- or radicand algorithm is used, which produces one bit per clock
cycle. Thus after 20 cycles the result is available in the SQRTOUT[2:0] registers.
Note: The interrupt signal is not connected to the interrupt controller of the MCU, because the result is
available after a defined period of 4 machine cycles. The programmer has to take care for the correct timing.
For instance, 4 NOP instructions must be inserted before reading out the result.
When writing SQRTIN[39:36] are don’t care.
When reading SQRTOUT[23:20] those bits equal zero.
Data Registers
SFR-Address
Name
E8h
SQRTIN0
Input value[7:0]
E9h
SQRTIN1
Input value[15:8]
EAh
SQRTIN2
Input value[23:16]
EBh
SQRTIN3
Input value[31:24]
ECh
SQRTIN4
Input value[39:32]
EDh
SQRTOUT0
Output value[7:0]
EEh
SQRTOUT1
Output value[15:8]
EFh
SQRTOUT2
Output value[19:16]
4
MOV SQRT4, #...
3
Description
2
4 cyc
0
MOV SQRT0, #...
MOV A, SQRT2, ...
square root
calculation
start calculation
result available
Figure 19: Timing diagram
During the time of calculation data must not be overwritten. As soon as the register SQRT0 is written, the
calculation sequence is retriggered and the result is calculated from the latest contents of the 5 input registers.
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Data Sheet AS8267 / AS8268
Boot Loader (BOOTLOAD)
After power-up the boot loader checks if the program memory (32kB Flash) is blank or if there is a program
available.
In case there is no program stored (no program length stored at 7FFFh and 7FFEh) the boot loader generates
‘SJMP$’ (Hex code: 80FEh) instruction address 0000h.
This guarantees a well defined behaviour after power-on.
In case there is a program stored in the Flash memory the boot load block loads also security information from
the upmost page of the Flash memory.
After the boot load the MCU will start to work.
The loaded program will be executed.
Watchdog Timer (WDT)
A watchdog timer is provided on-chip to automatically initiate a system reset if a ‘hold-off’ signal is not detected
within a predefined timeout period, by the watchdog.
The watchdog timer consists of a programmable timer driven either by the Mclk (main oscillator output
frequency), or the MCU clock (microcontroller unit clock). The watchdog timer timeout period is dependent
upon the programming of the WDTCLK register. When the watchdog times out, a reset signal is generated
which is OR-ed with the main system reset. Thus a watchdog timer reset is identical to a power on reset.
If the watchdog timer function is required, the watchdog is enabled by setting the WDTE register LSB (Bit 0).
As soon as this bit is enabled, the program must periodically access the WDTCLK register (either read or write)
to prevent the watchdog timer from timeout and thus resetting the device.
Register Name
Address
Reset Value
WDTE
9180h
xxxx.xxx0b
WDTCLK[1:0]
9181h
xxxx.xxx00b
Description
Enables or disables the watchdog timer function
0: watchdog disabled
1: watchdog enabled
A read or write access clears the watchdog timer. Writing
bits [1:0] selects the clock source.
x ........Don’t care
Watchdog Timer Enable Register (WDTE)
MSB
LSB
-
Bit
-
-
-
-
-
-
WDTE0
Symbol Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
-
Not used
2
-
Not used
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Data Sheet AS8267 / AS8268
Bit
Symbol Function
1
-
Not used
WDTE0 Disables and enables the watchdog timer function
0: watchdog disabled
1: watchdog enabled
0
The watchdog timer has a selectable counter length of 18 bit, 20 bit or 22 bit for the Mclk and 18 bits for the
mcu_clk. It should be noted that while the Mclk has a fixed frequency, depending on the crystal frequency, the
MCU clock is programmable, being divisible by 1 to 128, in binary steps (see MCUCLKDIV Register
(‘mcu_clk’)). The timeout periods below assume the Mclk = 3.579545MHz (fixed crystal frequency).
Watchdog Timer Clock Register (WDTCLK)
MSB
LSB
-
-
-
Bit
Symbol
Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
-
Not used
2
-
Not used
1
WDTCLK1
Watchdog timeout period
(Mclk = 3.579545MHz)
0
WDTCLK0
-
-
-
WDTCLK1
WDTCLK0
Clock Source
Timeout Period (ms)
Bit1
Bit0
Mclk – default after reset
Mclk
Mclk
Mcu_clk (div=1)
Mcuclk (div=128)
73.2
292.8
1171.2
73.2
9300
0
0
1
0
1
0
1
1
2 nd UART (UART2)
An additional serial interface, UART2 is provided for debugging purposes. UART2 is accessible via two of the
multi-purpose I/Os (MPIO). The UART2 is functionally identical to UART1. The SFR addresses are defined as
follows:
Register Name
Address
Description
SCON2
C0h
SBUF2
C1h
Serial port control register – see Serial Interface – UART1 for details.
Serial port buffer register – see Serial Interface – UART1 for details.
SBAUDL2
C2h
Baudrate reload register – Low address
SBAUDH2
C3h
Baudrate reload register – High address
SOVR2
B0h
‘Serial overflow’ register, which indicates when data in SBUF has been
overwritten before being read. The flag is the LSB with the other 7 bits all
being 0.
Below is an example how to configure the ports IO7 and IO6 as UART2s txd2 (IO7) and rxd2 (IO6) pins.
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Data Sheet AS8267 / AS8268
;------------------------------------------------------------------------------; Configure UART2 to the pins IO6 and IO7 with the Baudrate of 19200 Baud:
;------------------------------------------------------------------------------; map txd2 = IO7
; map rxd2 = IO6
;------------------------------------------------------------------------------xdata mem: OUTMUX1
(9503h) <- 80h ; maps txd2 to IO7
xdata mem: SET_ENO
(9505h) <- 80h ; enable output IO7
xdata mem: SEL_PUPDO (9509h) <- 40h ; enable pullup for IO6
xdata mem: SEL_IN
(950Bh) <- 05h ; map rxd2 to IO6
idata mem: SBAUDL2
(0C2)
<- 11h ; set Baudrate register low
idata mem: SBAUDH2
(0C3)
<- 00h ; set Baudrate register high
idata mem: SCON2
(0C0)
<- 50h ; setup UART2 serial port for Rx and Tx.
;------------------------------------------------------------------------------;------------------------------------------------------------------------------; program fragment for enabling uart2 for serial communication.
;
; sfr locations -;
SCON2
EQU
0C0h
; Serial 2 Control Register
SBUF2
EQU
0C1h
; Serial 2 Port Register
SBAUDL2
EQU
0C2h
; Serial 2 Baudload LowByte
SBAUDH2
EQU
0C3h
; Serial 2 Baudload HighByte
;
; variables -;
BaudrateLO
EQU
11
; Baudrate Value for 19200 baud,
BaudrateHI
EQU
0
; mcu_clk = 3.58MHz
;
; memory map for the uart2 configurations -;
OUTMUX1
EQU
09503H
; need to be set as 0x80
SET_ENO
EQU
09505H
; need to be set as 0x80
SEL_PUPDO
EQU
09509H
; need to be set as 0x40
SEL_IN
EQU
0950BH
; need to be set as 0x05
;
; instruction code fragment
; ...
MOV
IE,#0A0h
; enable serial interrupt UART2 0xA0
MOV
DPTR,#OUTMUX1
; 09503H <- 80h ; maps txd2 to IO7
MOV
A,#080h
MOVX
@DPTR,A
MOV
DPTR,#SET_ENO
; 09505H <- 80h ; enable output IO7
MOV
A,#080h
MOVX
@DPTR,A
MOV
DPTR,#SEL_PUPDO ; 09509H <- 40h ; enable pullup for IO6
MOV
A,#040h
MOVX
@DPTR,A
MOV
DPTR,#SEL_IN
; 0950BH <- 05h ; map rxd2 to IO6
MOV
A,#005h
MOVX
@DPTR,A
MOV
SBAUDL2,#BaudrateLO ; set Baudrate (16 bits)
MOV
SBAUDH2,#BaudrateHI
MOV
SCON2,#050h
; Set up uart2 serial port for Rx and Tx.
; ...
;-------------------------------------------------------------------------------
Timer 0
There is only Timer 0 present, Timer 1 is not implemented except for some flags in the TCON register, which
are also used for Timer 0. Furthermore, there is no counter mode available as the inputs T1 and INTO of the
standard 8051 are not mapped to external pins. The connection of Timer 0 in each of its four operating modes
is shown below.
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Data Sheet AS8267 / AS8268
There are five special function registers (SFR) related to the Timer 0:
Register Name
Address
TMOD
Description
89h
Timer mode register
TCON
88h
Timer control register
T0PRE
8Eh
Timer 0 8 bit prescaler register
TH0
8Ch
Timer 0 higher byte
TL0
8Ah
Timer 0 lower byte
TMOD
MSB
LSB
0
Bit
0
0
0
GATE
C/T_N
M1
M0
Symbol Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
GATE
Has no effect on Timer 0 operation can be used as register bit
2
C/T_N
Acts like an enable signal
1
M1
Mode Description
Mode select
0
M0
0
1
2
3
Bit1
Bit0
0
0
1
0
1
0
1
1
13 bit timer (MCS-48 compatible)
Same as mode 0 but 16 bit timer
Configures Timer 0 as 8 bit autoreload timer. Overflow from
TL0 sets TF0 and reloads TL0 with the value of TH0.
Two 8 bit timers, TL0 controlled by Timer 0 standard bits,
TH0 controlled by Timer 1 control bits but no interrupt
TCON
MSB
LSB
TF1
Bit
TR1
TF0
TR0
-
-
-
-
Symbol Function
7
TF1
Timer 0 (Mode 3) TH0 overrun flag, generates no interrupt, flag can be polled by software.
6
TR1
Timer 0 (Mode 3) TH0 enable flag, TH0 runs if ‘1’ in all other modes the flag has no effect.
5
TF0
4
TR0
Timer 0 overrun flag, generates an interrupt. Flag is cleared by hardware when the processor jumps to
the interrupt routine
Timer 0 run control bit. Timer runs if ‘1’. Cleared/set by software.
3
-
Not used
2
-
Not used
1
-
Not used
0
-
Not used
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Data Sheet AS8267 / AS8268
T0PRE
mcu_clk
1x1x
mcu_clk
6 N
: N
: 6
CT_N = 0
CT_N = 1
Control
TL0
TH0
(5 bits)
(8 bits)
TF0
Timer 0
Interrupt
TF0
Timer 0
Interrupt
(8bits) *)
TR0
*)
Figure 20: Timer 0 Mode 0 and Mode 1 : 13 bit counter
mcu_clk
: 6
1
mcu _ clk
6
T0PRE
1x1x
mcu_clk
6 N
: N
CT_N = 0
TL0
(8 bits)
CT_N = 1
Control
TR0
Reload
TH0
(8 bits)
Figure 21: Timer 0 Mode 2: 8 bit counter
mcu_clk
: 6
1
mcu _ clk
6
1x1x
mcu_clk
6 N
T0PRE
: N
TR1
CT_N = 0
TL0
CT_N = 1
TH0
(8 bits)
(8 bits)
TF1
Control
TF0
Timer 0
Interrupt
Control
TR0
Figure 22: Timer 0 Mode 3: two 8 bit counters
T0PRE
Unlike the standard 8051 there is a 8-bit prescaler register available for timer 0. Values of 0x00 (default after
reset) and 0x01 do not have any effect. For all other values the timer input frequency is divided according to
the value (ranging from 2 up to 255).
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Data Sheet AS8267 / AS8268
8.9
System Control (SCT)
The system control is responsible for handling different modes of operation such as normal mode (metering
functions) and test mode.
The clock generation and reset control are also available in System Control (SCT).
Modes of Operation
Power off
In this mode everything is off including the ‘System Timing and RTC’ block, provided that no battery is
connected to VDD_BAT or the battery is discharged. Nothing happens.
RTC on, Rest of the Chip off
In this mode the ‘System Timing and RTC’ block is supplied by a battery, the RTC is working, but no interrupts
are generated.
At the moment the battery is inserted, a power-on reset just for the RTC will be generated. The reset will be set
to 0 after the first clock edges arrive.
Power-up Phase
When the power is switched on (for the ‘rest’ of the chip), there is a power-on reset first and the reset is held
until the BOOTLOAD block has finished operation. The BOOTLOAD block will load information from the upmost
page (program available, security) from the internal Flash memory.
After BOOTLOAD the MCU will start executing the program in the Flash memory. It is assumed that at the
beginning of the program various system parameters are set (sel_i, sel_v, sel_p, creep etc.)
FLASH not programmed, must be loaded from outside
If the Flash does not contain a program the MCU will run in idle mode. It is necessary to write a program to the
Flash next.
Reset Chip: Externally triggered BOOTLOAD
When a (new) program has been written to the Flash it will be necessary to trigger a new BOOTLOAD
sequence. This can be done by generating a chip reset. After the related command has been detected by the
SCT on the UART1 interface the reset/boot sequence will start. Next the MCU will run the program from the
beginning.
This command can also be used for a simple reset.
Normal Operation
The MCU is working through its program, access to certain blocks/functions may be done via the UART
interfaces. For example, it may be required to read data from an external EEPROM or from the RTC block.
During these operations the MCU is not reset!
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Program Debugging
Program debugging can be done using a so-called monitor program, which may communicate with a PC using
the UART2 interface or the UART1 interface in direct access mode. In the AS8267 / AS8268 the SPI interface
(SPI2 and MCU) can also be used to access the whole XDATA address space.
Note: Direct access mode (‘dam’ register bit) turns off the command interpreter. If the MCU program performs
this operation, it must be able to clear the dam bit after the operation, or the SPI2 access must have the ability
to do this. If both possibilities are blocked there is no way out and the device is permanently locked.
To prevent this situation UART2 is recommended to be used as debug interface.
Read from XDATA Address
This command is used for Flash and external EEPROM read access.
Mainly for evaluation purposes it is possible to read all 64k of the XDATA address space. This includes all
registers, the X_RAM memory and the Flash memory. A dedicated command is reserved for this. The following
diagram shows the main blocks involved here:
External
EEPROM
SCT
DSP
RTC
MPIO
SPI
X_RAM
WDT
FLASH
LCDD
WRITE
READ
MASS_ERASE, PAGE_ERASE
SCT
UART1
TXD
RXD
Transmission Protocol:
In order to make the data transfer easier for the system control a defined protocol is used for talking to the
UART1, where also the length of the data to be read from the XDATA address space is specified at the
beginning of the transmission. It looks like this:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Read Command
(8 bits)
15
0
1
2
3
4
5
6
7
8
Start Address
(16 bits)
0
1
2
3
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
Block Length
(16 bits)
4
5
6
7
...
(TXD)
Data
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Data Sheet AS8267 / AS8268
Notes:
1) When ‘enable_crc’ is set to 1 a 16-bit checksum word will be sent after the data stream. It can be used to validate the
received data.
Before accessing the Flash a request has to be sent (see
2)
Arbitration)
Write to XDATA Address
This command is used for Flash and external EEPROM write access.
For evaluation, but also for setting the RTC it will be required to write to registers located in the XDATA
address space. Also for this an SCT command is prepared. The diagram in the section before shows the main
blocks involved. Again the whole XDATA range of 64k bytes is visible to the WRITE_X instruction. However, for
the Flash memory (including addresses 0000h to 7FFFh) there are some considerations to take when
programming the device. Besides the ‘byte write’ command, there are also ‘page write’, ‘page_erase’ and ‘mass
erase’.
Notes:
Before accessing the Flash a request has to be sent (see
1)
2)
Arbitration)
In principle it is possible that a value, which has been modified using this write-command, immediately gets overwritten
by the MCU. Therefore this command has to be used in an intelligent way.
Transmission Protocol:
In order to make the data transfer easier for the system control a defined protocol is used for talking to the
UART1, where also the length of the data to be written to the XDATA address space is specified at the
beginning of the transmission. It looks like this:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Write Command
(8 bits)
15
0
1
2
3
4
5
6
7
Start Address
(16 bits)
0
1
2
3
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
0
Block Length
(16 bits)
4
5
6
7
1
2
3
4
5
6
7
...
Data
(TXD)
Acknowledge
Notes:
1) When ‘enable_crc’ is set to 0 the UART1 only sends back the acknowledge word (FAh).
2) When ‘enable_crc’ is set to 1 a 16-bit checksum has to be transferred to the UART1 at the end of the data stream. The
SCT will calculate the checksum and depending on the result it will send back the acknowledge word (FAh) or the notacknowledge word (FBh).
Transmission Protocol for FLASH BYTE PROGRAM and FLASH PAGE PROGRAM:
The protocol is the same as for a manual write operation to a register. The only difference is that after reaching
the desired block length, a Flash program process is triggered, which takes 6ms maximum. The device detects
automatically a Flash programming process when selecting an address lower than 8000h. The user is
responsible for the correct programming and handling of Flash pages.
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Transmission Protocol for FLASH PAGE ERASE and FLASH MASS ERASE:
For ‘page erase’ and ‘mass erase’ there is also deployed the WRITE_X command.
[5:0]
don’t care
page address
Page Erase
0
1
2
3
4
5
6
7
0
XX
WRITE_X CMD
XXXX
1000
16 bit address
0000
0000
0000
8000h => page erase
[14:0]
don’t care
Mass Erase
0
1
2
3
4
5
6
7
0
XXX
WRITE_X CMD
XXXX
XXXX
16 bit address
XXXX
1100
0000
0000
0000
C000h => mass erase
addr (15) selects FLASH
For ‘page erase’ it is required to define the page to be erased. The erase code is 8000h in the block length
field.
For mass erase, the address field is recommended to be set to 0000h and the block length field to C000h.
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Flow Diagram of Operational Modes
VDD[D|A] off
VDD_BAT off
insert
battery
VDD[D|A] off
VDD_BAT on
power-up
(Vmain on)
power-up
(Vmains on)
VDD[D|A] on
VDD_BAT off:
- no clock
- chip stays reset
VDD[D|A] on
VDD_BAT on
Power-on
Reset
Program
execution
Command
mode disable
Command
mode enable
MCU:
Program execution,
Command mode
active
Finished.
Program
available
BOOTLOAD
Finished.
No program
MCU in idle mode,
"loop program"
running
Interrupt
from UART
Receiving
SCT command
UART
handling
Evaluating SCT
command
Receiving
SCT command
f0h
f6h
f1h
f2h
f3h
Reset
chip
BOOT
LOAD
Read
Prompt
8 bit out:
"A"
8 bit out:
"L"
8 bit out:
"I"
8 bit out:
"V"
8 bit out:
"E"
f4h
f5h
Set
Baudrate
Read
from ext.
EEPROM
Write to
ext.
EEPROM
Read
from
XDATA
Write to
XDATA
Set
password
SBaudH
16 bit
address
16 bit
address
16 bit
address
16 bit
address
8 bytes
password
SBaudL
16 bit
16 bit
16 bit
16 bit
blocklength blocklength blocklength blocklength
8 bit
data out
(...)
8 bit
data in
(...)
8 bit
data out
(...)
ACK /
NACK
Back to
MCU
Revision 1.0, 19-Jun-07
Back to
MCU
f7h/f8h
Back to
MCU
Back to
MCU
Back to
MCU
Back to
MCU
8 bit
data in
(...)
ACK /
NACK
ACK /
NACK
Back to
MCU
Back to
MCU
Page 114 of 136
Data Sheet AS8267 / AS8268
Command Interpreter
The command interpreter is continuously looking at the UART1 input and detects, if a command has been sent,
i.e. a specific byte that is defined to initiate a dedicated mode of operation (see the flow diagram above).
The commands have been specified to lie outside the “normal” ASCII range. All codes not specified within the
following table can directly be transferred to the MCU without any interference by the SCT.
Command Name
Code
Description
SOFT_RESET
F0h
Resets the chip and initiates a BOOTLOAD sequence, then the MCU program is
started.
RD_PROMPT
F1h
The chip sends a specific signature, “ALIVE”. This can be used to test the
UART1/SCT interface.
SBAUD
F2h
Makes it possible to set the UART1 baudrate from outside the chip by directly
accessing the SFRs “SBaudL” and SBaudH”.
Default setting: 11 (3.5795MHz crystal and 19200 Baud)
READ_EE
F3h
Enables reading of data from ext. EEPROM
WRITE_EE
F4h
Data can be written to the ext. EEPROM
READ_X
F5h
Data from the XDATA address space can be read.
WRITE_X
F6h
Data can be written to any location in the XDATA address space.
SET_PW
F7h
Set password
SET_PW1
F8h
Set password and enable attack counter
ACK
FAh
Acknowledge
NACK
FBh
No Acknowledge
SCT Registers
The system control (SCT) registers provide for the setting of various enables signals and selection of the MCU
clock (MCU_CLK) frequency.
Register Name Address Reset Value Description
-
9000h
-
enable signals
9001h
000b
See table below
mcuclkdiv[2:0]
9002h
000b
See table below
Revision 1.0, 19-Jun-07
Not used
Page 115 of 136
Data Sheet AS8267 / AS8268
Enable Signals Register
The enable signals register includes power-down signals and other control signals.
MSB
LSB
-
sel_spi2
enable_crc
Bit
Symbol
Function
7
-
Not used
6
sel_spi2
u2clkoff
u1clkoff
dam
sdmi2_pd
afe_pd
Selects the SPI path
0: selects path to SPI_Flash (slave mode)
1: selects path to SPI2 (master mode)
enable_crc Enables checksum functionality during read/write accesses to XDATA address space or
EEPROM. If enabled, a 16-bit checksum word (see Note below) is sent after the data, which is
checked by the SCT (in case of ‘write’) or can be checked by an external component (in case of
‘read’).
0: checksum disabled
1: checksum enabled
5
4
u2clkoff
Switches off the UART2 clock (which is also running at the highest system frequency ‘mclk’):
0: clock active
1: clock switched off
3
u1clkoff
Switches off the UART1 clock (which is running at the highest system frequency ‘mclk’):
0: clock active
1: clock switched off
2
dam
1
sdmi2_pd
0
afe_pd
Select direct access mode for UART1; in case of ‘dam’ input data will no longer be interpreted as
commands.
0: direct access mode off 1: dam on
Set power-down for current channel 2 (active high)
0: no power-down
1: I2 powered down
Set power-down for the entire analog front end (AFE)
0: AFE powered up
1: AFE powered down
16
12
5
Note: The checksum is calculated using the following formula: g(x) = x + x + x + 1
In dam mode no interrupt will be triggered, therefore the SCON register has to be polled.
MCUCLKDIV Register (‘mcu_clk’)
The MCU clock divider (mcuclkdiv) divides down the main clock (Mclk) which is the output from the low power
oscillator.
Division of the mcu_clk frequency is provided to enable low power operating modes, for example when the
AS8267 / AS8268 ICs are in a battery operating mode, when VDDD is connected to a battery.
MSB
LSB
-
-
-
Bit
Symbol
Function
7
-
Not used
6
-
Not used
5
-
Not used
4
-
Not used
3
-
Not used
Revision 1.0, 19-Jun-07
-
-
mcuclkdiv.2
mcuclkdiv.1
mcuclkdiv.0
Page 116 of 136
Data Sheet AS8267 / AS8268
Bit
2
1
0
Symbol
Function
mcuclkdiv.2 These bits set the mcu_clk frequency by dividing down
the main clock (Mclk).
mcuclkdiv.1
mcuclkdiv.0
Revision 1.0, 19-Jun-07
Bit2
Bit1
Bit0
Division
0
0
0
Mclk : 1
0
0
1
Mclk : 2
0
1
0
Mclk : 4
0
1
1
Mclk : 8
1
0
0
Mclk : 16
1
0
1
Mclk : 32
1
1
0
Mclk : 64
1
1
1
Mclk : 128
Page 117 of 136
Data Sheet AS8267 / AS8268
8.10 Serial Interface – UART1
-
Extended version of the standard 8051 UART1
SBUF and SCON are compatible with standard 8051
Built-in 16 bit baudrate generator (SBAUDH, SBAUDL)
Additional SOVR receiver overflow indicator register
UART1 is used to communicate externally. UART1 requires only two pins to receive and transmit information.
UART1 is compatible to the Serial Interface of the 8051 microcontroller family, with the exception of the
baudrate generation. UART1 is functionally identical to UART2. Thus the instructions below are also valid for
UART2.
UART1 is segmented into three main functional blocks, namely Baudrate, Transmission and Reception, as
shown in the block diagram below:
Transmission
TxD
Transmit Unit
TB8
EndOfTransmission
RI or TI
Interrupt
Transmit
Baudrate Timer
SCON
SCON
Register
16 bit
Baudrate
Generator
Baudrate
SBAUDH,
SBAUDL
Receive
Baudrate Timer
Start
Reception
Reception
SOVR
EndOfReception,
RB8
SBUF
Receive
SBUF
Receive
Shift Enable
Receive
Shifter
Data(0...7)
Detected Bit
Receive
Control
Receive
Bit Detector
RxD
Figure 23: UART1 block diagram
There is no direct dependency on osc clock (Mode 0, 3). Instead there is a built-in 16 bit wide baudrate
generator for higher flexibility.
Revision 1.0, 19-Jun-07
Page 118 of 136
Data Sheet AS8267 / AS8268
UART is dedicated to the SCT block for writing to and reading from other functional blocks such as RTC,
LCDD; besides, it is used for selection of different modes of operation.
SFRs of UART1
There are five special function registers dedicated to the UART1.
Register Name
Address Description
Read/Write from MCU
SCON
98h
Serial port control register
read & write
SBUF
99h
Serial port buffer register
read & write (separate)
SBAUDL
9Ah
Baudrate reload register – Low address
write only
SBAUDH
9Bh
Baudrate reload register – High address
write only
SOVR
90h
Serial receive buffer overflow register
read & write, only one bit
(=bit0) available
SOVR Register
Serial receive buffer overflow register. If data is received before it has been read out of SBUF then the bit SOV
is set. It can the cleared by software. All other bits of SOVR are 0.
SOVR
MSB
LSB
0
0
0
0
0
0
0
SOV
Note:
Overflow flag. If ‘1’ then a receiver buffer overflow occurred. The old buffer value has been overwritten by new
incoming data. Set by overflow, cleared by MCU.
SCON Register
The SFR Serial Port Control Register (SCON) is used to configure the UART1 and to check the status of the
transmission.
SCON
MSB
SM0
LSB
SM1
Revision 1.0, 19-Jun-07
SM2
REN
TB8
RB8
TI
RI
Page 119 of 136
Data Sheet AS8267 / AS8268
Bit
Symbol Function
Mode
7
SM0
6
SM1
5
SM2
4
REN
3
TB8
2
RB8
1
TI
0
RI
Bit7
Bit6
Mode 0: same as Mode 1, (Mode 0 is not implemented due to
0
0
standard 8051)
0
1
Mode 1: 8-bit UART1, variable Baudrate. - The serial transmission
is set to 8 data bits. However up to 10 bits can be sent at port TxD
and received at port RxD: start bit (always ‘0’), eight data bits (LSB
first), and a stop bit (always ‘1’). The value of a received stop bit is
Mode select
transferred to SCON.RB8 and can be evaluated by the software.
flags
1
0
Mode 2: 9-bit UART1, variable Baudrate. - The serial transmission
is set to 9 data bits. However up to 11 bits can be sent at port TxD
and received at port RxD: start bit (always ‘0’), nine data bits (LSB
first), and a stop bit (always ‘1’). The value of SCON.TB8 is used
for transmitting the ninth data bit (usually as parity bit). The value
of the received ninth data bit is transferred to SCON.RB8 and can
be evaluated by the software.
Mode 3: 9-bit UART1, variable Baudrate. – same as Mode 2.
1
1
Mode Select Flag 2: Enables the multiprocessor communications feature in Mode 2.
Mode 0: SM2 is not used.
Mode 1: When SM2=’1’, RI is not set and SBUF is not loaded if the received stop bit is ‘0’.
Mode 2: When SM2=’1’, RI is not set and SBUF is not loaded if the received ninth data bit is ‘0’. Please
refer also to section Multiprocessor Communications.
Receiver Enable Flag. With REN=’0’ the receiver is disabled, otherwise enabled. REN is to be set and
cleared by the software.
Value of the ninth data bit to be sent when in mode 2.
Value of the ninth data bit received when in mode 2 or value of the stop bit received when in mode 1.
Not used in mode 0.
Transmit Interrupt Flag. This flag is set by the UART1 at the end of transmitting. In mode 0 flag TI is set
at the end of the eighth data bit, in all others modes at the beginning of the stop bit. Flag TI must be
cleared by the software.
Receive Interrupt Flag. This flag is set by the hardware at the end of receiving. In mode 0 flag RI is set
at the end of the eighth data bit, in mode 1 at the middle of the stop bit, and in mode 2 at the middle of
the ninth data bit. Flag RI must be cleared by the software.
Note:
1) Mode Select Flags 0/1: These bits are used to select one of four transmission modes. In all four modes the
baudrate is determined by the Baudrate Generator.
SBUF Registers
The 8-bit register SBUF is the data buffer register which actually consists of two registers for both transmitting
and receiving data. Both are accessed by the same address SBUF. A write access to SBUF is redirected into
the internal register TransmitSBUF, a read access to SBUF is redirected to the internal register ReceiveSBUF.
Remark: The (optional) ninth data bit is defined in SCON.TB8/RB8.
SBUF
MSB
Data 7
LSB
Data 6
Revision 1.0, 19-Jun-07
Data 5
Data 4
Data 3
Data 2
Data 1
Data 0
Page 120 of 136
Data Sheet AS8267 / AS8268
Note:
The SBUF register is split up within the UART1 into the internal registers TransmitSBUF (when writing to the
SFR) and ReceiveSBUF (when reading from the SFR)
A write access to SBUF starts a transmission, according to the selected mode. A write access during an
ongoing transmission results in discarding the byte without disturbing the process of transmission. If there is a
series of bytes to be transmitted, the software has to wait until the previous byte has been sent (SCON.TI =
‘1’), before writing to SBUF. The shift sequence (serialization) is handled by means of the internal register
TransmitSBUF that holds up to 12 bits (depending on the mode used): hardcoded ‘1’-bit + start bit + 8 data bits
+ optional ninth data bit + stop bit. During transmitting the content of TransmitSBUF is shift right, thus
transmission is done with LSB first.
A read access to SBUF delivers the latest byte received by the UART1. Bit SCON.RI has to be cleared (to ‘0’)
by the software after fetching a byte from SBUF, thus enabling the UART1 to receive further bytes. If SCON.RI
is not ‘0’ when a new byte is received, the new byte will be discarded (and thus is lost) and SBUF will keep its
old value.
SBAUDH, SBAUDL Baudrate Reload Registers
MSB
LSB
SBAUDL
BR7
BF6
BR5
BR4
BR3
BR2
BR1
BR0
SBAUDH
BR15
BR14
BR13
BR12
BR11
BR10
BR9
BR8
Note:
The SBAUDL and SBAUDH are merged into a 16 bit reload value:
SBAUDL = Baudrate value (7:0)
SBAUDH = Baudrate value (15:8)
Baudrate Generator
Unlike the original 8051 architecture, the UART1 incorporates a built-in baudrate generator. The baudrate is
generated by a counter, which is decremented every clock cycle. When reaching the value 0, the counter is
automatically reloaded. The reload value is a programmable value stored in the 16 bit register formed by
SBAUDH and SBAUDL. A serial bit (during transmit and receive) is further divided into 16 time slices for
accurate sampling. Due to the full-duplex operation there is a separate Transmit Baudrate Timer und Receive
Baudrate Timer implemented for this task.
Baudrate Reload Register
The following table shows some selected values to be loaded to the BRReloadRegister (SBaudH + SBaudL) at
a given clock frequency that may be used with the AS8267 / AS8268 ICs. The smaller the value, the more
difficult it is to meet a demanded baudrate within a given tolerance. If the error is greater than 5% the baudrate
is not appropriate for error-free communication.
Baudrate
[Baud]
3.00MHz
error [%]
3.58MHz
(3579545Hz)
error [%]
4.00MHz
error [%]
110
1704
0.0267
2033
0.0082
2272
0.0120
150
1249
0
1491
-0.0320
1666
0.0200
Revision 1.0, 19-Jun-07
Page 121 of 136
Data Sheet AS8267 / AS8268
Baudrate
[Baud]
3.00MHz
error [%]
3.58MHz
(3579545Hz)
error [%]
4.00MHz
error [%]
300
624
0
745
0.0351
832
-0.0400
600
312
0.1597
372
0.0350
416
0.0799
1200
155
-0.1603
185
-0.2337
207
-0.1603
2400
77
-0.1603
92
-0.2337
103
-0.1603
4800
38
-0.1603
46
0.8326
51
-0.1603
9600
19
2.3438
22
-1.3232
25
-0.1603
19200
9
2.3438
11
2.8986
12
-0.1603
38400
4
2.3438
5
2.8986
(6)
Æ6.9940
57600
(2)
Æ-8.5069
3
2.8986
(3)
Æ-8.5069
76800
(1)
Æ-22.0703
2
2.8986
(2)
Æ-8.5069
115200
(1)
Æ18.6198
1
2.8986
(1)
Æ-8.5069
Below there are the formulas for calculating Baudrate and BaudrateReloadRegister, but also the error. You
have to divide through 16 because the serial bit is further divided into 16 time slices.
Baudrate =
ClockFrequency
16 × (1 + BaudrateReloadRegister )
BaudrateReloadRegister =
ClockFrequency
−1
16 × Baudrate
ClockFrequency
16 × (1 + Baudrate Re load Re gister )
desired _ baudrate
desired _ baudrate −
error =
Transmission
A write access to register SBUF invokes the transmission of a byte. If there is already an ongoing transmission
then the written byte is discarded. At the end of transmission flag SCON.TI is set, indicating the software that
the next byte can be written to SBUF.
Reception
The process of receiving is initiated by setting SCON.REN to ‘1’ and SCON.RI to ‘0’ by software. After
reception the UART1 sets SCON.RI to ‘1’ and the data bits can be fetched from SBUF. Each data bit of the
serial data stream is probed three times (in the middle of the bit time) to achieve noise immunity.
Interrupt
Per default the UART1 is operated in the ‘command mode’ (as described in section SCT) and an interrupt is
asserted to the MCU except when a command is detected. The UART1 can also be used in the direct access
mode (bit dam = ‘1’ in SCT register 9001h). This setting allows the MCU to operate the UART1 as defined in
the standard 8051 configuration.
Revision 1.0, 19-Jun-07
Page 122 of 136
Data Sheet AS8267 / AS8268
The UART1 asserts an interrupt whenever flag SCON.RI is ‘1’ or SCON.TI is ‘1’. These flags are set if a
successful receive or transmit operation has taken place. The flags to SCON.RI and SCON.TI must be cleared
by software. The MCU program branches to the interrupt routine if the serial interrupt is enabled in the IE
register, with IE.4 (= ES) = ‘1’. Since SCON.RI and SCON.TI are linked together (logic-or), there is a common
interrupt service routine for both transmitting and receiving. The interrupt service routine has to decide which
event triggered the interrupt request (by querying the flags RI and TI). It is important to clear the flags before
leaving the interrupt service routine.
Multiprocessor Communications
th
Mode 2 has a special provision for multiprocessor communications. In this mode, a 9 data bit is received and
goes into RB8. Then a stop bit follows.
The port can be programmed such that when the stop bit is received, the serial port interrupt will be activated
only if RB8 = 1. This feature is enabled by setting bit SM2 in SCON. A way to use this feature in multiprocessor
systems is as follows:
When the master processor wants to transmit a block of data to one of several slaves, it first sends out an
address byte which identifies the target slave. An address byte differs from a data byte in that the ninth bit is 1
in an address byte and 0 in a data byte. With SM2 = 1, no slave will be interrupted by a data byte. An address
byte, however, will interrupt all slaves, so that each slave can examine the received byte and see if it is being
addressed. The addressed slave will clear its SM2 bit and prepare to receive the data bytes that will be
coming. The slaves that were not being addressed leave their SM2s set and go on about their business,
ignoring the coming data bytes.
Modes
The UART1 can be used in two different modes: mode 0 (= mode 1) and mode 2 (= mode 3). The mode
selection is due the bits SM0, SM1 in the SCON register.
Mode 0 and 1
8 bit UART1 with variable baudrate controlled by the baudrate generator.
WrStrobeSFR
TransmitEnable
TransmitSBUF
001000010010
000100001001
Start Bit
1
000010000100 000001000010
000000100001 000000010000
000000001000
000000000100
0
0
000000000010
Transmitting
EndOfTransmission
TxD
0
0
1
0
0
Stop Bit
TI
Figure 24: Transmitting in mode 1: here ‘09h’ is sent. The resulting bit stream on the TxD line is:
start bit (=‘0’) + ‘10010000’, for LSB is sent first.
The process of transmitting is initiated by writing to SBUF. The byte written to SBUF is held in register
TransmitSBUF . The transmission starts with the next 1-pulse on the internal signal TransmitEnable . Output TxD is
driven with a start bit (‘0’), eight data bits with the LSB first shifted out from TransmitSBUF , and a stop bit (‘1’). At
Revision 1.0, 19-Jun-07
Page 123 of 136
Data Sheet AS8267 / AS8268
begin of the stop bit the internal signal EndOfTransmission is activated, causing flag SCON.TI going to high and
thus indicating the end of the transmission.
ReceiveShiftEnable
Start
0
Bit
RxD
0
1
1
0
1
1
1
1
Stop Bit
RB8
RI
StartReception
Receiving
EndOfReception
ReceiveShiftRegister
ReceiveSBUF
011111111
001111111
100111111
110011111
011001111
101100111
110110011
111011001
111101100
F6
00
Figure 25: Receiving in mode 1 and mode 2: Here the bit stream ‘0’+’01101111’ is received (see signal ReceivedDataBit), that is:
start bit + F6h. The start bit is the first 0-pulse of signal RxD, that is when signal ReceivingStartbit is active.
Receiving is only possible when SCON.REN = ‘1’. The process of receiving is started with a falling edge on RxD
(internal signal StartReceiption is activated) and controlled by a 4-bit counter, that means a bit time is divided into
16 time slices. The counter is reset when identifying a falling edge on RxD and is consequently synchronized.
The value of RxD is probed three times at the counter stage 6, 7, and 8 (counter range is from 0 to 15). The
final value ( ReceivedData-Bit ) is determined by majority. The multiple probing ensures a more robust serial
connection.
At counter = 9 the received bit is transferred into the shift register ( ReceiveShiftRegister ). If the first received bit
(stop bit) is not ‘0’, then the process is aborted and the UART1 waits for the next falling edge on RxD . Due to
this procedure all data packets with an invalid start bit are automatically discarded.
When receiving the stop bit ( EndOfReceiption = ‘1’) the following condition is checked:
SCON.RI=’0’ and (SCON.SM2=’0’ or Received_Stop_Bit=’1’)
If this condition is true, then all eight data bits are transferred to ReceiveSBUF , the stop bit is written to
SCON.RB8, and SCON.RI is set to ‘1’. Otherwise all the received data is discarded and the receiver waits for
the next falling edge on RxD .
Mode 2 and 3
9 bit UART1 with variable baudrate controlled by the baudrate generator.
Mode 2 is very similar to mode 1 except that nine data bits are processed. The subsequent text deals only the
differences to mode 1. Mode 3 is the same as Mode 2.
The ninth data bit during transmission is taken from SCON.TB8 and is sent after the eight bits from SBUF.
When receiving the ninth data bit ( EndOfReceiption = ‘1’) the following condition is checked:
SCON.RI=’0’ and (SCON.SM2=’0’ or Ninth_Data_Bit=’1’)
Revision 1.0, 19-Jun-07
Page 124 of 136
Data Sheet AS8267 / AS8268
If this condition is true, then all eight data bits are transferred to ReceiveSBUF , the ninth data bit is transferred to
SCON.RB8, and SCON.RI is set to ‘1’. Otherwise all the received data is discarded and the receiver waits for
the next falling edge on RxD .
Assembler Code
The following code fragments demonstrate the programming of the UART1.
Adjusting the Baudrate (for all modes)
SBL equ 9AH
SBH equ 9BH
; Serial BaudrateReload LowByte
; Serial BaudrateReload HighByte
mov SBL,#38
mov SBH,#0
; 9600 baud, 6MHz
Using Mode 0
mov
mov
clr
mov
SCON,#00H
A,#53H
TI
SBUF,A
; mode 0, REN=0, RI=0, TI=0
; clear transmit flag
; transmit 53H in mode 0
wait:
jnb TI,wait
; wait until data is sent
mov SCON,#10H
clr REN
; mode 0, REN=1 - start reception
; REN=0
jnb RI,wait
mov A,SBUF
; wait until data is received
; move received byte into the accu
wait:
Transmitting in Mode 0
mov
mov
clr
mov
SCON,#50H
A,#53H
TI
SBUF,A
; mode 1, REN=1, RI=0, TI=0
; clear transmit flag
; transmit 53H in mode 1
wait:
jnb TI,wait
; wait until data is sent
Receiving in Mode 1 (only bytes with valid stop bit)
mov SCON,#70H
; mode 1, SM2=1, REN=1, RI=0, TI=0
jnb RI,wait
clr RI
mov A,SBUF
; wait until data is received
; enable another reception
; move received byte to accu
wait:
Transmitting in Mode 2 (ninth data bit as parity bit)
mov
mov
mov
mov
A,#0A4h
C,P
TB8,C
SBUF,A
;
;
;
;
move data to accu
parity information to carry flag
parity information to ninth data bit
transmit A4H in mode 2
wait:
jnb TI,wait
; wait until data is sent
Interrupt Based Receiving
org 0h
Revision 1.0, 19-Jun-07
; reset vector
Page 125 of 136
Data Sheet AS8267 / AS8268
ljmp program_start
org 023h
ljmp SerialInterrupt
org 100
SerialInterrupt:
clr RI
mov P1, SBUF
reti
program_start:
setb EA
setb ES
; serial interrupt vector
; begin of main program
; clear the RI bit (since we know that was
; the bit that caused the interrupt)
; move the received data out to port one
; enable interrupts generally
; enable serial interrupts
mov SCON,#50H
mov SBUF,#2FH
clr RI
; mode 1, REN = 1
jmp LOOP
; endless loop
; ensure that RI is cleared
LOOP:
Interrupt Based Transmitting
org 0h
ljmp program_start
; reset vector
org 023h
ljmp SerialInterrupt
; serial interrupt vector
org 100
SerialInterrupt:
...
...
clr TI
reti
program_start:
setb EA
setb ES
mov SCON,#40H
mov SBUF,#2FH
Revision 1.0, 19-Jun-07
; begin of main program
; enable interrupts generally
; enable serial interrupts
; mode 1, REN = 0
Page 126 of 136
Data Sheet AS8267 / AS8268
9. Circuit Diagram
N
L
IC3
D5
R13
C22
VI
VO
3.3V
GND
C21
ZD1
L1
+
C23
LCD
R1
LSD9
LSD10
LSD11
LSD12
LSD13
LSD14
LSD15
LSD8
49
50
51
52
53
54
55
LSD17
LSD18
LSD16
56
57
58
59
LSD20
43
7
42
IO0
IO1
48
IC1
AS8267 / AS8268
8
9
41
40
10
39
11
1
2
13
38
14
35
IO4
15
34
IO5
16
33
32
XIN
31
VDD_BAT
30
RXD
29
TXD
28
IO11
27
IO10
26
IO9
17
IO6
25
VSSD
SC
C14
36
24
VDDD
MOSI
3.3V
37
23
IO3
22
IO2
I/Os
Examples only
LSD19
6
VSSA
LOAD
60
44
VDDA
C11
LSD21
5
VDDD
S_N
C10
61
45
I2N
3.3V
LSD22
46
4
I2P
R12
C9
3
I1P
21
R11
47
20
R10
1
2
I1N
C8
63
LSD23
R9
C7
VP
VN
MISO
VSSD
R8
C6
62
C5
19
C4
R7
18
C3
R6
IO8
RSH
IO7
C2
R5
R4
CT1
R3
AS8268 only
C1
kWh
Vrms
Irms
12
64
R2
LSD7
LSD6
LSD5
LSD4
LSD3
LSD2
LSD1
LSD0
LBP3
LBP2
LBP1
LBP0
n.c.
n.c.
RES_N
XOUT
XTAL
3.3V
D1
C15
3.3V
D2
C20 +
D3
D4
BAT
AS8268 only
C13
VDDD
C16 +
HOLD
VDDA
C12 +
VCC
3.3V 3.3V
3.3V
C17
IC2
(optional)
C19
Revision 1.0, 19-Jun-07
C18
+
3.3V
Page 127 of 136
Data Sheet AS8267 / AS8268
10.
Parts List
Designation
Value
Unit
Description
IC1
AS8267 / AS8268 Metering Integrated Circuits
IC2
Up to 32kB SPI Bus EEPROM (selectable in binary steps)
IC3
3.3
V
RSH
300
µOhm
Voltage regulator LE33CZ
Shunt resistor (see ‘Analog Front End’)
CT1
Current transformer
R1
Resistor (see ‘Analog Front End’)
R2
470
Ohm
Resistor (see ‘Analog Front End’)
R3
470
Ohm
Resistor
R4
680
Ohm
Resistor
R5
680
Ohm
Resistor
R6
680
Ohm
Resistor
R7
680
Ohm
Resistor
R8
680
Ohm
Resistor
R9
680
Ohm
Resistor
R10
4.7
Ohm
Resistor (see ‘Analog Front End’)
R11
680
Ohm
Resistor
R12
680
Ohm
Resistor
R13
470
Ohm
Resistor
C1
100
nF
Capacitor
C2
100
nF
Capacitor
C3
33
nF
Capacitor
C4
33
nF
Capacitor
C5
33
nF
Capacitor
C6
33
nF
Capacitor
C7
33
nF
Capacitor
C8
33
nF
Capacitor
C9
33
nF
Capacitor
C10
33
nF
Capacitor
C11
100
nF
Capacitor
C12
220
µF
Capacitor
C13
100
nF
Capacitor
C14
10
nF
Capacitor
C15
10
nF
Capacitor
C16
1.0
µF
Capacitor
C17
100
nF
Capacitor
Revision 1.0, 19-Jun-07
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Data Sheet AS8267 / AS8268
Designation
Value
Unit
Description
C18
1.0
µF
Capacitor
C19
100
nF
Capacitor
C20
1.0
µF
Capacitor
C21
10
nF
Capacitor
C22
0.47
µF
Capacitor
C23
470
µF
Capacitor
D1
Diode 1N4148
D2
Diode 1N4148
D3
Diode 1N4148
D4
Diode 1N4148
D5
Diode 1N4004
ZD1
15
V
L1
BAT
Varistor
3.0
V
LCD
XTAL
Zener diode BZV85–C15
Lithium battery
Liquid crystal display
3.579545
MHz
Crystal
Note: The external components for the programmable multi-purpose I/Os (MPIO) are not included in the above
parts list, as they depend on the specific meter functional requirements.
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Data Sheet AS8267 / AS8268
11.
Packaging
LQFP64
12.
Product Ordering Guide
Device Number
MPIO
LCDD
Temperature
Package
9
20 x 4
-40°C to 85°C
LQFP64
Tray in DryPack
AS8267 BLQW
9
20 x 4
-40°C to 85°C
LQFP64
T & R in DryPack
AS8268 BLQS
12
24 x 4
-40°C to 85°C
LQFP64
Tray in DryPack
AS8268 BLQW
12
24 x 4
-40°C to 85°C
LQFP64
T & R in DryPack
AS8267 BLQS
Revision 1.0, 19-Jun-07
Packing
Page 130 of 136
Data Sheet AS8267 / AS8268
13.
Collection of Formulae
Shunt resistor for mains current sensing:
Rshunt =
Vp
Ip
Where V p is the peak input voltage to the IC at rated conditions and I p the peak Imax value of the meter.
CT voltage setting termination resistor for mains current sensing:
R VS =
Vin(p )
IL 2
Where V in(p) is the peak input voltage to the IC at rated conditions (V mains ; I max ). i.e.: If Gain = 4 then V in(p) must
be set at 150mVpeak and I L is the CT RMS secondary current at rated conditions (V mains ; I max )
Voltage divider for the V mains input for the energy calculation:
Vmains
R1A+R1B
R2
Vin
R1A + R1B = R2 ×
( Vmains − Vin(P ) )
Vin(P )
Where V mains is the peak mains voltage and V in(P) is the is the peak input voltage to the IC at rated conditions.
Phase shift value of 1 unit of phase correction relative to the mains frequency:
1unit = 360° ×
t ovs
f
f
= 360° × mains = 360° × mains
tmains
fovs
fosc / 8
Phase = # unit × 360° ×
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fmains
fosc / 8
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Data Sheet AS8267 / AS8268
Where fmains is the mains frequency and fOSC is the oscillator frequency.
Phase correction factor with a power factor (PF) of less than 1:
The meter has been calibrated at PF = 1 and the error is approximately 0 for I cal (calibration current). If the PF
is reduced, the effect of phase differences results in an increased error (‘phase_error’):
First, the related phase shift in degrees can be calculated using the following formula:
⎛ ⎛ phase _ error [%] ⎞
⎞
phase _ shift = arc cos⎜⎜ ⎜1 +
⎟ × cos 60° ⎟⎟ − 60°
100
⎠
⎝⎝
⎠
Where the phase_error is the measured error in percentage and cosΦ is the phase angle.
For phase_error = 9.2[%] the phase_shift is 3.0°.
For f osc = 3.579545MHz and f mains = 50Hz one phase correction unit represents 2.41’, which is
0.04023°.
Thus the phase correction factor must be set to
3.0°
= 74.57 units
0.04023°
= 75 units.
The pcorr register has to be set to 4bh.
RMS values from the voltage (sos_v) and current (sos_i1 and sos_i2):
Vrms =
Irms =
nsamp
1 nsamp 2
Vi , where ∑ Vi2 is the sos_v value
∑
nsamp i=1
i =1
1
nsamp
nsamp
∑
i=1
Ii2 ,
nsamp
where
∑
i =1
Ii2 is the sos_i value
Where nsamp, the number of samples before an update rate of the MDR (meter data register), is selected to
achieve coherent sampling.
16-bit calibration values for the voltage (V) and current (I) channels:
The ideal values after RMS calculations of voltage (V in of 100mVp at rated conditions) and current and (I in of
30mVp at rated conditions when Gain = 20) are:
RMS_V(ideal) = 479 (rms)
RMS_I (ideal) = 292,100 (rms)
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Data Sheet AS8267 / AS8268
Due to non-ideal components a different RMS value is calculated: RMS_I(actual). From this, the required
calibration factor is calculated using the following formula:
cal _ i =
RMS _ I(ideal)
RMS _ I(actual)
The following formula calculates the actual value to be programmed into the calibration registers (cal_v; cal_i1;
cal_i2):
cal _ i(reg) = hex(round(cal _ i × 32,768 ))
Fast internal pulse rate (PR int ):
The Fast Pulse Gen output always has the same relationship with the LED pulse rate, which is defined by
mconst. Only if LED is calibrated to a meter constant different from those provided in the mconst table, will the
fast internal pulse rate be different.
PR int = 204,800 ×
T arg et Pulse Rate
[i / kWh ]
mconst
Where mconst is the meter constant.
1i =
1,000 × 3,600
[Ws ]
PRint
Active power calibration (Pulse_lev):
The Pulse_lev is specified such that a typical pulse rate of 204,800i/kWh can be achieved.
During energy pulse calibration the correct Pulse_lev is determined in order to get the desired pulse rate.
The IC default value for Pulse_lev is defined for I max =40A and V mains =230V.
Default Pulse_lev:
570,950
The formula for calculating the ideal Pulse_lev is as follows:
Pulse _ lev(ideal) =
230 V
40 A
×
× Pulse _ lev( default )
Vmains Imax
The standard or reference meter pulses are counted between two pulses from the meter under test. From the
deviation the corrected Pulse_lev may be calculated.
Pulse _ lev(corrected) = Pulse _ lev(ideal) ×
Ni
,
Na
Where Ni is the ideal number of pulses and Na is the actual number of pulses (pcnt register in MPIO).
The ideal number of pulses Ni is the ratio between the pulse rates, which is always >1. The formula for Ni is as
follows:
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Data Sheet AS8267 / AS8268
Ni =
PR(ref )
LED Pulse Rate(mconst )
Where PR(ref) is the reference meter constant.
LED Meter Constant (non-standard):
The LED pulses are derived directly from the fast internal pulses (204,800i/kWh) and is specified using the
parameter ‘mconst’ of SREG. If the target meter constant is different from one of the selectable (mconst) meter
constants, the following formula applies:
(Ideal Pulse _ lev ×
Ni
)
Na
Where Ni is calculated using the Target Pulse Rate:
Ni =
Re ference Meter Cons tan t
T arg et Pulse Rate
NB: For mconst, select a pulse rate close to Target Pulse Rate, so that the Pulse_lev stays within reasonable
limits.
Temperature Sensor:
The AS8267 / AS8268 ICs include an on-chip temperature sensor which allows for temperature correction over
the entire operating temperature range of the device.
The actual temperature value is calculated by the means of the following formula:
Temp [°C] = ( Temp _ corrected × 0.193 ) − 75
Temp_corre cted = TS_Result [15 : 0] + TS_OffsetC orr [15 : 0]
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Data Sheet AS8267 / AS8268
14.
Terminology
AFE
CT
DSP
EEPROM
I_RAM
kB
LBPx
LCD
LCDD
LED
LP_DIV
LP_OSC
LSB
LSDx
MCU
MDR
MPIO
MSB
P_ACCU
PF
PLP
PSM
PSW
RAM
RES_N
RMS
RTC
SCT
SDM
SFR
SQRT
SREG
SPI
UART
VREF
WDT
X_RAM
X_DATA
-
Revision 1.0, 19-Jun-07
Analog front end
Current transformer
Digital signal processor
Electrically erasable programmable read only memory
8051 internal memory
kilobyte
LCD back-plane driver pin
Liquid crystal display
Liquid crystal display driver
Light-emitting diode
Low power divider
Low power oscillator
Least significant bit
LCD segment driver pin
Microcontroller unit
Meter data register (in DSP block)
Programmable multi-purpose input/output
Most significant bit
Power accumulator for real power
Power factor
Power low pass filter
Power-supply monitor
Program status word
Random access memory
System reset pin
Root mean square
Real time clock
System control
Sigma-delta modulator
Special function register
Square root block
Settings register (in DSP block)
Serial peripheral interface
Universal asynchronous receiver/transmitter
Voltage reference
Watchdog timer
8051 external data memory
64kByte address space
Page 135 of 136
Data Sheet AS8267 / AS8268
15.
Revision
Revision
1.0
16.
Date
Owner
19-Jun-07
hza
Description
Copyright
Copyright © 1997-2007, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted,
merged, translated, stored, or used without the prior written consent of the copyright owner.
17.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions
appearing in its Terms of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by
description regarding the information set forth herein or regarding the freedom of the described devices from
patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time
and without notice. Therefore, prior to designing this product into a system, it is necessary to check with
austriamicrosystems AG for current information. This product is intended for use in normal commercial
applications. Applications requiring extended temperature range, unusual environmental requirements, or high
reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not
recommended without additional processing by austriamicrosystems AG for each application.
The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However,
austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not
limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect,
special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing,
performance or use of the technical data herein. NO obligation or liability to recipient or any third party shall
arise or flow out of austriamicrosystems AG rendering of technical or other services.
18.
Contact
austriamicrosystems AG
A 8141 Schloss Premstaetten, Austria
T. +43 3136 500 0
F. +43 3136 525 01
[email protected]
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