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Multi-function watt-hour meter communication protocol DL/T 645-1997 
1. Range 
The standardization is used for the tariff device of multi-function watt-hour meter to do point to 
point or one master to multi-slaves data exchange with hand-held unit(HHU) or other data terminal 
equipments. It defines the technical specification of physical connection, communication link and 
application. 
4 Physical layer 
…………………………………………………. 
4.1.6 Electrical characteristics of reading head 
The reading head should be able to do data exchange with data terminal equipment. Its 
communication interface is TTL level, or according to ITU-TV.24 and ITU-TV.28. The 
electrical characteristics of reading head are shown in fig.4. 
4.1.6.1 Working limit of reading head 
Signal level 
OFF status ON status 
Binary “1” Binary “0” 
MARK SPACE 
Switch off light source Switch on light source 
<-3V(V.28) >+3V(V.28) 
<=0.8V(TTL input) >=2V(TTL input) 
-0.5V~0.4V(TTL output) 2.4V~Up(TTL output) 
Note: TTL negative logic is used here. 
4.1.6.2 Transfer speed 
Max transfer speed should be no lower than 2400bps. 
4.1.7 Power supply for working 
The power supply of reading head is provided by hand-held unit or other data terminal 
equipment connected with it. 
a) 
0 1 0 1 
(b) 
ON 0 1 0 1 
Fig.5 signal and modulation 
a) electrical signal with no modulation b)infrared light signal after modulation 
Fig.6 angle of light radiation 
OFF 
q
4.2 Infrared light interface of modulation type 
4.2.1 Modulation characteristics 
The modulation of the signal is as Fig.5. The carrier frequency is 38kHz±1kHz 
4.2.2 Optical characteristics 
4.2.2.1 Reference temperature 23℃±2℃ 
4.2.2.2 Half-angle of light radiation q 
q ³15° (as Fig.6) 
4.2.2.3 Wave length 
The wave length of infrared light is 900nm~1000nm 
4.2.2.4 Emitter 
The emitter produces infrared light with irradiance Ee/r ³50mW/m2 on the light axis 1m 
away from the surface of emitter 
4.2.2.5 Receiver 
The irradiance Ee/r of the receiver on the light axis 10mm away from the surface of receiver 
should satisfy following conditions: 
Irradiance of infrared light Status of receiver 
0.35mW/m2£Ee/r £20000mW/m2 ON 
Ee/r £0.2mW/m2 OFF 
4.2.2.6 Environment condition of the light 
According to 4.1.5.4, the valid distance of communication is longer than 4m under the 
environment. 
4.2.3 Electrical characteristics 
It's according to 4.1.6, but transfer speed should be no higher than 1200bps. 
4.2.4 Use condition 
4.2.4.1 It's should be avoided that strong light (sunlight and fluorescent light) directly irradiate the 
receiving window of infrared light receiver. 
4.2.4.2 It should be tried to keep the optical axis of the receiver consistent with that of the emitter 
when working. 
4.2.4.3 Avoid of appearing multiple consecutive“0” in the data. 
4.3 Electrical interface of serial port RS-485 
RS-485 is used by the standardization which make it's possible for multi-points connection. The 
general performance of RS-485 interface should accord with following specification. 
4.3.1 Electrostatic discharge (ESD) resistance of driver and receiver side is ±15V (human-body 
model) 
4.3.2 Common mode input voltage: -7V~+12V. 
4.3.3 Differential mode input voltage: upper than 0.2V 
4.3.4 Output voltage of driver: When the impedance of load is 54, the max output voltage of 
driver is 5V and the min is 1.5V. 
4.3.5 Tri-state output 
4.3.6 Half-duplex communication mode 
4.3.7 The driven capability should be no less than 32 interfaces of the same type 
4.3.8 The valid distance of transfer should be no less than 1200m when the transfer speed is no 
higher than 100kbps. 
4.3.9 The bus is passive power. The tariff device or data terminal equipment provide isolation 
power for it.
5 Data-link layer 
The protocol uses communication mode of master-slave structure and half-duplex. The 
hand-held unit or other data terminal is master station and tariff device is salve station. Each tariff 
device has its own address code. The creation and release of communication link is controlled by 
the master station sending information frame. Each frame is composed of 7 parts including start 
flag, address field of slave station, control code, data length, data field, check code of frame and end 
flag, in which each part is composed of several bytes. 
5.1 Byte format 
Transfer direction 
dDvdirection 
D2 0 D0 D1 D3 D4 D5 D6 D7 P 1 
Start bit Data of 8 bits Even check bit Stop bit 
Fig.7 transfer sequence of byte 
Instruction Code 
Frame start flag 68H 
Address field A0 
A1 
A2 
A3 
A4 
A5 
Frame start flag 68h 
Control code C 
Data length L 
Data DATA 
Check code CS 
End flag 16H 
Fig.8 Frame format 
Each byte has 8 bits binary code. A start bi t (0), an even check bit and a stop bit are added when 
transferring. So the total is 11 bits. The sequence of transfer is as Fig.7. The D0 is the LSB (least 
significant bit) and D7 is the MSB (most significant bit). The transfer order is that the bit in 
lower address is transferred first and then the bit in higher address. 
5.2 Frame format 
The frame is the basic unit for transferring information. The frame format is shown in fig.8.
5.2.1 Frame start flag: indicate the start of one frame, its value is 68H=01101000B 
5.2.2 Address field A0~A5: The address field comprises 6 bytes and each byte is composed of 2 
BCD codes. It can express the address with 12 decimal digits at most. The address can be ID of 
meter, or asset number, user number or device number, and so on which can be decided by users. 
When the length of address is less than 6 bytes, the rest bytes can be filled with hexadecimal 
number AAH. The lower address code is prior while higher one is in the latter. It's a broadcast 
address when the address value is 999999999999H. 
5.2.3 Control code: the format of control code is as following: 
Function code 
D7 D6 D5 D4 D3 D2 D1 D0 
Flag of subsequent frame 
Flag indicates whether slave station is abnormal 
Transfer direction 
D7=0: command frame from master station 
D7=1: response frame from slave station 
D6=0: slave station response correctly 
D6=1: slave station response abnormally 
D5=0: no subsequent data frame 
D5=1: has subsequent data frame 
D4~D0: function code of request and response 
00000: reserved 
00001: read data 
00010: read subsequent data 
00011: re-read data 
00100: write data 
01000: correcting time by broadcast 
01010: write device address 
01100: change communication speed 
01111: change password 
10000: clear maximum demand
5.2.4 Data length L: L describes the bytes number of data field. L<=200 when reading data, L <=50 
when writing data, and L=0 indicates no data. 
5.2.5 Data field DATA: data field can be data identifier, data or password, etc whose structure 
change with different control codes. The sender adds 33H to each byte when transferring while the 
receiver subtract 33H from each byte when received. 
5.2.6 Check code CS: It's the sum with modular operation on 256 of all bytes from the start flag to 
the byte before check code namely it's binary arithmetic sum of each byte deducting overflowing 
value over 256. 
5.2.7 End flag 16H: indicates the end of the frame, its value is 16H=00010110B 
5.3 Transfer 
5.3.1 Front-leading bytes 
To awaken the receiver, it should send FEH with 1~4 bytes before sending the frame. 
5.3.2 Transfer order 
All items in data field should be transferred with the order that the byte in lower position 
should be transferred firstly and then the bytes in higher position. 
For example, if power energy value is 123456.78kWh, the transfer order is as fig.9. 
CS 
AB 89 67 45 78 56 34 12 
5.3.3 Transfer response 
Each communication is initiated by master station with request command frame to slave station. 
The requested slave station responses according to the request which is described by control 
code in the command frame. 
Td----Response delay after command frame 33H 
is received: 20ms<=Td<=500ms 
Tb----Pause time between bytes: Tb<=500ms 
5.3.4 Error control 
78 56 34 12 AB 89 67 45 
.................................... 
5.3.5 Transfer speed 
initial speed: 1200bps 
standard speed: 300,600,1200,2400,4800,9600bps 
special speed: defined by manufacturer 
5.3.3 Response of transfer 
33H 
CS 
Fig.9 Transfer order 
Each communication starts from master station sending request command to slave station 
which is selected according to address code in the frame. Then the slave station responses 
according to the control code in command frame. 
Response delay Td after command frame is received: 20ms£ Td£500ms 
Pause time between bytes Tb: Tb£500ms 
5.3.4 Error control 
Byte check use even check method while frame check uses checksum of longitudinal bytes 
in frame. The receiver should discard the frame and not response when even check or checksum 
is wrong.
6 Data identifier 
6.1 Classification of data 
Except measurement value, the counting value, happen time of max demand, instantaneous 
voltage, electric current and power value are classified as variable; the calendar, time, user 
setting value, characteristic word and status word of tariff device, tariff period are classified as 
parametric variable. 
6.2 Structure and code of data identifier 
Tariff device stores all kinds of data with different types and attributes. The standardization 
use four-layers tree structure to represent these data. It uses 4 fields in two bytes to represent 
type and attribute of data respectively. These two bytes are DI1 and DI0 which is divided into 
four fields DI1H, DI1L, DI0H and DI0L where DI0L is the least significant filed and DI1H is the most 
significant field. 
DI1H describes type of data and is shown as following: 
DI1 
DI1H DI1L 
D7 D6 D5 D4 D3 D2 D1 D0 
1001 power energy 
1010 max demand 
1011 variable 
1100 parametric variable 
1101 load curve 
1110 user self defined 
1111 reserved 
DI1L, DI0H and DI0L describe different attributes of data. For the data of energy and max demand 
which have multiple attributes such as attribute of time domain(current value, value of last 
month, value of the month before last month), classification attribute(active, reactive), attribute 
of power direction(positive, negative), tariff attribute( total amount, amount of different tariff) 
and so on, their identifier is shown in 6.2.1 and 6.2.2. 
6.2.1 Data identifier of energy 
DI1 
DI1H DI1L 
D7 D6 D5 D4 D3 D2 D1 D0 
1001 Energy 00 currently 00 active 
01 last month 01 reactive 
10 month before last month 10 reserved 
11 collection 11 collection 
DI0 
DI0H DI0L 
D7 D6 D5 D4 D3 D2 D1 D0
DI0 
DI0H DI0L 
D7 D6 D5 D4 D3 D2 D1 D0 
0001 positive energy 0000 total energy 
0010 negative energy 0001 tariff 1 
0011 reactive power in 1st quadrant 0010 tariff 2 
0100 reactive power in 4th quadrant …. 
0101 reactive power in 2nd quadrant 1110 tariff k 
0011 reactive power in 3rd quadrant 1111 collection of local data block 
0111~1110 reserved 
1111 collection 
The coding of all data identifier of energy is shown in table A1. 
6.2.2 Data identifier of max demand 
DI1 
DI1H DI1L 
D7 D6 D5 D4 D3 D2 D1 D0 
1010 max demand 00 currently 00 active 
01 last month 01 reactive 
10 month before last month 10 reserved 
11 collection 11 collection 
DI0 
DI0H DI0L 
D7 D6 D5 D4 D3 D2 D1 D0 
0001 positive active max demand 0000 total energy 
0010 negative active max demand 0001 tariff 1 
0011 reactive power in 1st quadrant 0010 tariff 2 
0100 reactive power in 4th quadrant …. 
0101 reactive power in 2nd quadrant 1110 tariff k 
0011 reactive power in 3rd quadrant 1111 collection of local data block 
0111~1110 reserved 
1111 collection 
The coding of all data identifier of max demand is shown in table A2. 
6.2.3 According to the data classification of the standardization, the happen time of max demand is 
classified as variable. It is listed in table A3 individually which has same code but different type 
symbol (A, B) with corresponding max demand considering the convenience for data terminal 
reading data. The identifier codes of other data which are classified as variable and parametric 
variable are listed in table A4, A5. 
6.2.4 The identifier code of load record data block is listed in table A6.There is no definition about 
the format and data length of this data in related standardization, so it can be self-defined by user. 
6.3 Data set 
6.3.1 Brief introduction 
The identifier code of data represents single data item or collection of data items. A single data
item can be denoted uniquely by identifier code of corresponding data item in appendix A. The 
identifier code of data block and data set can be used when requesting to access data set which 
is composed of multiple data items. 
6.3.2 Data item, data block and data set 
6.3.2.1 Data item 
They are some BCD codes which reflect a certain time-space value or digital value in tariff 
device. For example, 9010H in NO. 1 in appendix A represents current positive active 
energy whose format is XXXXXX.XX(kWh). 
6.3.2.2 Data block 
The data block is a group of data composed of continuous data items whose identifier fields 
DI1H, DI1L, DI0H is same while DI0L is different (0,1,2,...,k(k is the possible maximum) in data 
identifier. The identifier feature of data block is DI0L=1111B. 
6.3.2.3 Data set A data set is composed of 1 or more data blocks. In data identifier, it is a data set 
when DI1H, DI1L, DI0H is 1111B or 11B, which is composed of all possible value of the filed 
and multiple data blocks in its next field. At this condition, no matter what value of its next 
field is, it’s viewed as a data set identifier namely 11B or 1111B. 
Then end flag of each data block which constitute the data set is AAH when 
transferring. Tow continuous AAH represents a null data block. As Fig.10, the data set has 
four data blocks in which data block 1 has m1 data and data block 2 has m2 data, data block 
3 has no data, and data block 4 has m4 data, 
Data block 1(m1) 
AAH 
Data block 2(m2) 
AAH 
AAH 
AAH 
Data block 3(0) 
Data block 4(m4) 
m1 
m2 
m3 
m4 
Fig.10 data set when transferring 
6.3.3 Example of identifier of data set 
a) identifier code DI1DI0=9010H(data item) 
represents current positive active energy 
b)identifier code DI1DI0=901FH(data block) 
represents current positive total energy and the set of energy with all tariff (total energy, 
energy of tariff 1, tariff 2, ....tariff k) 
c)identifier code DI1DI0=90F0H(data set) 
represents current positive and negative active energy. Is is make up of two items namely 
9010H(current positive active energy) and 9020H(current negative active energy). 
According to 6.3.2.3, the identifier is viewed as same with 90FFH. 
d)identifier code DI1DI0=90FFH(data set)
represents the set of current positive and negative active energy which has 2(k+1) items 
totally from 9010H to 902kH in table A1. 
7 Application layer 
7.1 Read data 
7.1.1 Request frame from master station 
function: request reading data 
control code: C=01H 
data length: L=02H 
frame format: 
68H A0 … A5 68H 01H 02H DI0 DI1 CS 16H 
Data length 
Control code 
Identifier of data 
7.1.2 Normally response from slave station 
function: slave station response normally 
control code: C=81H, no subsequent data frame 
C=A1H, has subsequent data frame 
data length: L=02H+m(data length) 
format of no subsequent data frame: 
68H A0 … A5 68H 81H L DI0 DI1 N1 … Nm CS 16H 
format of has subsequent data frame: 
Data identifier 
Data length 
Control code 
68H A0 … A5 68H C1H 01H ERR CS 16H 
7.1.3 Salve station response abnormally 
function: slave station receives wrong request or no corresponding data 
control code: C=C1H 
data length: L=01H 
frame format: 
Data item
68H A0 … A5 68H C1H 01H ERR CS 16H 
Note: for error information word, please refer appendix B5. 
7.2 Read subsequent data 
7.2.1 Request frame from master station 
function: request reading subsequent data 
control code: C=02H 
data length: L=02H 
frame format: 
68H A0 … A5 68H 02H 02H DI0 DI1 CS 16H 
7.2.2 Slave station response normally 
function: subsequent data is transferred according to the format of normal data frame 
control code: C=82H, no subsequent data frame 
C=A2H, has subsequent data frame 
data length: L=02H+m(data length) 
format of no subsequent data frame : 
68H A0 … A5 68H 82H L DI0 DI1 N1 … Nm CS 16H 
format of has subsequent data frame: 
68H A0 … A5 68H A2H L DI0 DI1 N1 … Nm CS 16H 
7.2.3 Salve station response abnormally 
function: slave station receives wrong request or no corresponding data 
control code: C=C2H 
data length: L=01H 
frame format: 
68H A0 … A5 68H C2H 01H ERR CS 16H 
7.3 Re-read data 
7.3.1 Request frame from master station 
function: request slave station re-transferring the data in last frame 
control code: C=03H 
data length: L=00H 
frame format: 
68H A0 … A5 68H 03H 00H CS 16H 
7.3.2 Slave station response normally 
control code: C=83H, no subsequent frame 
C=A3H, has subsequent frame 
data length: L=02H+m(data length) 
Error information word
format of no subsequent frame : 
68H A0 … A5 68H 83H L DI0 DI1 N1 … Nm CS 16H 
format of has subsequent frame: 
68H A0 … A5 68H A3H L DI0 DI1 N1 … Nm CS 16H 
7.3.3 Salve station response abnormally 
control code: C=C3H 
data length: L=01H 
frame format: 
68H A0 … A5 68H C3H 01H ERR CS 16H 
7.4 Write data 
7.4.1 Request frame for writing data 
function: master station requests slave station to set data(or program) 
control code: C=04H 
data length: L=02H+m(data length) 
frame format: 
68H A0 … A5 68H 04H L DI0 DI1 N1 … Nm CS 16H 
7.4.2 Slave station response normally 
function: slave station notify the executing result of the request to master station 
control code: C=84H 
data length: L=00H 
frame format 
68H A0 … A5 68H 84H 00H CS 16H 
7.4.3 Salve station response abnormally 
control code: C=C4H 
data length: L=01H 
frame format: 
68H A0 … A5 68H C4H 01H ERR CS 16H 
7.5 Correcting time with broadcast 
function: make the time of slave station is synchronous with master slave 
control code: C=08H 
data length: L=06H 
data field: YYMMDDhhmmss (year.month.day.hour.minute.second) 
frame format: 
68H 99H … 99H 68H 08H 06H ss mm hh 
DD MM YY CS 16H 
1. It doesn't need response for correcting time with broadcast
2.Only when the time difference between slave station and master station is under ±5min, it 
executes correcting time command by setting the time of slave station same with that in the 
command. 
3. It doesn't recommend correcting time at 0 clock in case that it will affect some regular 
operations at 0 clock. 
4. It allows correcting time only once every day. 
7.6 Write address of device 
7.6.1 Request for write address of device 
function: set address code for some slave station 
control code: C=0AH 
address field: 99...99H 
data length: L=06H 
data field: A0...A5 (address code of device) 
frame format 
68H 99H … 99H 68H 0AH 06H A0 … A5 CS 16H 
Note: The request uses broadcast address, which requires the slave station that is set address has 
corresponding key (switcher) cooperating with the command. The slave station whose key is 
pressed during the period of master station broadcasting request will response, others will not 
response. 
7.6.2 Slave station response normally 
function: the device which execute the request correctly responses 
control code: C=8AH 
address field: A0...A5 (new address code of the device) 
data length: L=00H 
frame format 
68H A0 … A5 68H 8AH 00H CS 16H 
7.7 change communication speed 
7.7.1 request for changing communication speed 
function: request new communication speed other than 1200bps 
control code: C=0CH 
data length: L=01H 
frame format: 
68H A0 … A5 68H 8CH 01H Z CS 16H 
7.7.2 salve station response with confirmation 
Feature word of speed 
function: slave station confirms the request of changing communication speed 
control code: C=8CH 
data length: L=01H
frame format: 
7.7.3 Slave station deny the request of changing communication speed 
68H A0 … A5 68H 8CH 01H Z CS 16H 
control code: C=8CH 
data length: L=01H 
data field: Z=FFH, represent deny 
frame format: 
Same with feature word in request 
speed 
68H A0 … A5 68H 8CH 01H FFH CS 16H 
7.8 change password 
7.8.1 Request for changing password 
function: change current password of slave station 
control code:C=0FH 
data length:L=08H 
data field: PAoP0oP1oP2oPANP0NP1NP2N 
frame format: 
68H A0 … A5 68H 0FH 08H PAo P0o P1o P2o PAN P0N P1N P2N CS 16H 
P0oP1oP2o is original password or password with higher authority. PAo represent authority of the 
password; P0NP1NP2N represents new password or password that need be set. 
PAN is the authority of new password. The data range of PAo,PAN is 0~9 which 0 is the 
highest authority. The number is larger while the authority is lower. The level of authority is divided 
into highest, programming and clear max demand. 
7.8.2 Slave station response normally 
function: slave station notify changing password correctly 
control code: C=8FH 
data length: L=04H 
data field: authority of password and password PANP0NP1NP2N 
frame format: 
68H A0 … A5 68H 8FH 04H PAN P0N P1N P2N CS 16H 
7.8.3 slave station doesn't response when it go wrong 
7.9 Clear max demand 
7.9.1 request for clearing max demand 
function: for tariff device which is working on non-automatically meter reading mode, the 
command can implement clearing max demand and data rolling of energy in current month, last 
month, the month before last month and register of max demand. 
Control code:C=10H 
data length: L=00H 
frame format: 
68H A0 … A5 68H 10H 00H CS 16H
DLT645 protocol english version

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DLT645 protocol english version

  • 1. Multi-function watt-hour meter communication protocol DL/T 645-1997 1. Range The standardization is used for the tariff device of multi-function watt-hour meter to do point to point or one master to multi-slaves data exchange with hand-held unit(HHU) or other data terminal equipments. It defines the technical specification of physical connection, communication link and application. 4 Physical layer …………………………………………………. 4.1.6 Electrical characteristics of reading head The reading head should be able to do data exchange with data terminal equipment. Its communication interface is TTL level, or according to ITU-TV.24 and ITU-TV.28. The electrical characteristics of reading head are shown in fig.4. 4.1.6.1 Working limit of reading head Signal level OFF status ON status Binary “1” Binary “0” MARK SPACE Switch off light source Switch on light source <-3V(V.28) >+3V(V.28) <=0.8V(TTL input) >=2V(TTL input) -0.5V~0.4V(TTL output) 2.4V~Up(TTL output) Note: TTL negative logic is used here. 4.1.6.2 Transfer speed Max transfer speed should be no lower than 2400bps. 4.1.7 Power supply for working The power supply of reading head is provided by hand-held unit or other data terminal equipment connected with it. a) 0 1 0 1 (b) ON 0 1 0 1 Fig.5 signal and modulation a) electrical signal with no modulation b)infrared light signal after modulation Fig.6 angle of light radiation OFF q
  • 2. 4.2 Infrared light interface of modulation type 4.2.1 Modulation characteristics The modulation of the signal is as Fig.5. The carrier frequency is 38kHz±1kHz 4.2.2 Optical characteristics 4.2.2.1 Reference temperature 23℃±2℃ 4.2.2.2 Half-angle of light radiation q q ³15° (as Fig.6) 4.2.2.3 Wave length The wave length of infrared light is 900nm~1000nm 4.2.2.4 Emitter The emitter produces infrared light with irradiance Ee/r ³50mW/m2 on the light axis 1m away from the surface of emitter 4.2.2.5 Receiver The irradiance Ee/r of the receiver on the light axis 10mm away from the surface of receiver should satisfy following conditions: Irradiance of infrared light Status of receiver 0.35mW/m2£Ee/r £20000mW/m2 ON Ee/r £0.2mW/m2 OFF 4.2.2.6 Environment condition of the light According to 4.1.5.4, the valid distance of communication is longer than 4m under the environment. 4.2.3 Electrical characteristics It's according to 4.1.6, but transfer speed should be no higher than 1200bps. 4.2.4 Use condition 4.2.4.1 It's should be avoided that strong light (sunlight and fluorescent light) directly irradiate the receiving window of infrared light receiver. 4.2.4.2 It should be tried to keep the optical axis of the receiver consistent with that of the emitter when working. 4.2.4.3 Avoid of appearing multiple consecutive“0” in the data. 4.3 Electrical interface of serial port RS-485 RS-485 is used by the standardization which make it's possible for multi-points connection. The general performance of RS-485 interface should accord with following specification. 4.3.1 Electrostatic discharge (ESD) resistance of driver and receiver side is ±15V (human-body model) 4.3.2 Common mode input voltage: -7V~+12V. 4.3.3 Differential mode input voltage: upper than 0.2V 4.3.4 Output voltage of driver: When the impedance of load is 54, the max output voltage of driver is 5V and the min is 1.5V. 4.3.5 Tri-state output 4.3.6 Half-duplex communication mode 4.3.7 The driven capability should be no less than 32 interfaces of the same type 4.3.8 The valid distance of transfer should be no less than 1200m when the transfer speed is no higher than 100kbps. 4.3.9 The bus is passive power. The tariff device or data terminal equipment provide isolation power for it.
  • 3. 5 Data-link layer The protocol uses communication mode of master-slave structure and half-duplex. The hand-held unit or other data terminal is master station and tariff device is salve station. Each tariff device has its own address code. The creation and release of communication link is controlled by the master station sending information frame. Each frame is composed of 7 parts including start flag, address field of slave station, control code, data length, data field, check code of frame and end flag, in which each part is composed of several bytes. 5.1 Byte format Transfer direction dDvdirection D2 0 D0 D1 D3 D4 D5 D6 D7 P 1 Start bit Data of 8 bits Even check bit Stop bit Fig.7 transfer sequence of byte Instruction Code Frame start flag 68H Address field A0 A1 A2 A3 A4 A5 Frame start flag 68h Control code C Data length L Data DATA Check code CS End flag 16H Fig.8 Frame format Each byte has 8 bits binary code. A start bi t (0), an even check bit and a stop bit are added when transferring. So the total is 11 bits. The sequence of transfer is as Fig.7. The D0 is the LSB (least significant bit) and D7 is the MSB (most significant bit). The transfer order is that the bit in lower address is transferred first and then the bit in higher address. 5.2 Frame format The frame is the basic unit for transferring information. The frame format is shown in fig.8.
  • 4. 5.2.1 Frame start flag: indicate the start of one frame, its value is 68H=01101000B 5.2.2 Address field A0~A5: The address field comprises 6 bytes and each byte is composed of 2 BCD codes. It can express the address with 12 decimal digits at most. The address can be ID of meter, or asset number, user number or device number, and so on which can be decided by users. When the length of address is less than 6 bytes, the rest bytes can be filled with hexadecimal number AAH. The lower address code is prior while higher one is in the latter. It's a broadcast address when the address value is 999999999999H. 5.2.3 Control code: the format of control code is as following: Function code D7 D6 D5 D4 D3 D2 D1 D0 Flag of subsequent frame Flag indicates whether slave station is abnormal Transfer direction D7=0: command frame from master station D7=1: response frame from slave station D6=0: slave station response correctly D6=1: slave station response abnormally D5=0: no subsequent data frame D5=1: has subsequent data frame D4~D0: function code of request and response 00000: reserved 00001: read data 00010: read subsequent data 00011: re-read data 00100: write data 01000: correcting time by broadcast 01010: write device address 01100: change communication speed 01111: change password 10000: clear maximum demand
  • 5. 5.2.4 Data length L: L describes the bytes number of data field. L<=200 when reading data, L <=50 when writing data, and L=0 indicates no data. 5.2.5 Data field DATA: data field can be data identifier, data or password, etc whose structure change with different control codes. The sender adds 33H to each byte when transferring while the receiver subtract 33H from each byte when received. 5.2.6 Check code CS: It's the sum with modular operation on 256 of all bytes from the start flag to the byte before check code namely it's binary arithmetic sum of each byte deducting overflowing value over 256. 5.2.7 End flag 16H: indicates the end of the frame, its value is 16H=00010110B 5.3 Transfer 5.3.1 Front-leading bytes To awaken the receiver, it should send FEH with 1~4 bytes before sending the frame. 5.3.2 Transfer order All items in data field should be transferred with the order that the byte in lower position should be transferred firstly and then the bytes in higher position. For example, if power energy value is 123456.78kWh, the transfer order is as fig.9. CS AB 89 67 45 78 56 34 12 5.3.3 Transfer response Each communication is initiated by master station with request command frame to slave station. The requested slave station responses according to the request which is described by control code in the command frame. Td----Response delay after command frame 33H is received: 20ms<=Td<=500ms Tb----Pause time between bytes: Tb<=500ms 5.3.4 Error control 78 56 34 12 AB 89 67 45 .................................... 5.3.5 Transfer speed initial speed: 1200bps standard speed: 300,600,1200,2400,4800,9600bps special speed: defined by manufacturer 5.3.3 Response of transfer 33H CS Fig.9 Transfer order Each communication starts from master station sending request command to slave station which is selected according to address code in the frame. Then the slave station responses according to the control code in command frame. Response delay Td after command frame is received: 20ms£ Td£500ms Pause time between bytes Tb: Tb£500ms 5.3.4 Error control Byte check use even check method while frame check uses checksum of longitudinal bytes in frame. The receiver should discard the frame and not response when even check or checksum is wrong.
  • 6. 6 Data identifier 6.1 Classification of data Except measurement value, the counting value, happen time of max demand, instantaneous voltage, electric current and power value are classified as variable; the calendar, time, user setting value, characteristic word and status word of tariff device, tariff period are classified as parametric variable. 6.2 Structure and code of data identifier Tariff device stores all kinds of data with different types and attributes. The standardization use four-layers tree structure to represent these data. It uses 4 fields in two bytes to represent type and attribute of data respectively. These two bytes are DI1 and DI0 which is divided into four fields DI1H, DI1L, DI0H and DI0L where DI0L is the least significant filed and DI1H is the most significant field. DI1H describes type of data and is shown as following: DI1 DI1H DI1L D7 D6 D5 D4 D3 D2 D1 D0 1001 power energy 1010 max demand 1011 variable 1100 parametric variable 1101 load curve 1110 user self defined 1111 reserved DI1L, DI0H and DI0L describe different attributes of data. For the data of energy and max demand which have multiple attributes such as attribute of time domain(current value, value of last month, value of the month before last month), classification attribute(active, reactive), attribute of power direction(positive, negative), tariff attribute( total amount, amount of different tariff) and so on, their identifier is shown in 6.2.1 and 6.2.2. 6.2.1 Data identifier of energy DI1 DI1H DI1L D7 D6 D5 D4 D3 D2 D1 D0 1001 Energy 00 currently 00 active 01 last month 01 reactive 10 month before last month 10 reserved 11 collection 11 collection DI0 DI0H DI0L D7 D6 D5 D4 D3 D2 D1 D0
  • 7. DI0 DI0H DI0L D7 D6 D5 D4 D3 D2 D1 D0 0001 positive energy 0000 total energy 0010 negative energy 0001 tariff 1 0011 reactive power in 1st quadrant 0010 tariff 2 0100 reactive power in 4th quadrant …. 0101 reactive power in 2nd quadrant 1110 tariff k 0011 reactive power in 3rd quadrant 1111 collection of local data block 0111~1110 reserved 1111 collection The coding of all data identifier of energy is shown in table A1. 6.2.2 Data identifier of max demand DI1 DI1H DI1L D7 D6 D5 D4 D3 D2 D1 D0 1010 max demand 00 currently 00 active 01 last month 01 reactive 10 month before last month 10 reserved 11 collection 11 collection DI0 DI0H DI0L D7 D6 D5 D4 D3 D2 D1 D0 0001 positive active max demand 0000 total energy 0010 negative active max demand 0001 tariff 1 0011 reactive power in 1st quadrant 0010 tariff 2 0100 reactive power in 4th quadrant …. 0101 reactive power in 2nd quadrant 1110 tariff k 0011 reactive power in 3rd quadrant 1111 collection of local data block 0111~1110 reserved 1111 collection The coding of all data identifier of max demand is shown in table A2. 6.2.3 According to the data classification of the standardization, the happen time of max demand is classified as variable. It is listed in table A3 individually which has same code but different type symbol (A, B) with corresponding max demand considering the convenience for data terminal reading data. The identifier codes of other data which are classified as variable and parametric variable are listed in table A4, A5. 6.2.4 The identifier code of load record data block is listed in table A6.There is no definition about the format and data length of this data in related standardization, so it can be self-defined by user. 6.3 Data set 6.3.1 Brief introduction The identifier code of data represents single data item or collection of data items. A single data
  • 8. item can be denoted uniquely by identifier code of corresponding data item in appendix A. The identifier code of data block and data set can be used when requesting to access data set which is composed of multiple data items. 6.3.2 Data item, data block and data set 6.3.2.1 Data item They are some BCD codes which reflect a certain time-space value or digital value in tariff device. For example, 9010H in NO. 1 in appendix A represents current positive active energy whose format is XXXXXX.XX(kWh). 6.3.2.2 Data block The data block is a group of data composed of continuous data items whose identifier fields DI1H, DI1L, DI0H is same while DI0L is different (0,1,2,...,k(k is the possible maximum) in data identifier. The identifier feature of data block is DI0L=1111B. 6.3.2.3 Data set A data set is composed of 1 or more data blocks. In data identifier, it is a data set when DI1H, DI1L, DI0H is 1111B or 11B, which is composed of all possible value of the filed and multiple data blocks in its next field. At this condition, no matter what value of its next field is, it’s viewed as a data set identifier namely 11B or 1111B. Then end flag of each data block which constitute the data set is AAH when transferring. Tow continuous AAH represents a null data block. As Fig.10, the data set has four data blocks in which data block 1 has m1 data and data block 2 has m2 data, data block 3 has no data, and data block 4 has m4 data, Data block 1(m1) AAH Data block 2(m2) AAH AAH AAH Data block 3(0) Data block 4(m4) m1 m2 m3 m4 Fig.10 data set when transferring 6.3.3 Example of identifier of data set a) identifier code DI1DI0=9010H(data item) represents current positive active energy b)identifier code DI1DI0=901FH(data block) represents current positive total energy and the set of energy with all tariff (total energy, energy of tariff 1, tariff 2, ....tariff k) c)identifier code DI1DI0=90F0H(data set) represents current positive and negative active energy. Is is make up of two items namely 9010H(current positive active energy) and 9020H(current negative active energy). According to 6.3.2.3, the identifier is viewed as same with 90FFH. d)identifier code DI1DI0=90FFH(data set)
  • 9. represents the set of current positive and negative active energy which has 2(k+1) items totally from 9010H to 902kH in table A1. 7 Application layer 7.1 Read data 7.1.1 Request frame from master station function: request reading data control code: C=01H data length: L=02H frame format: 68H A0 … A5 68H 01H 02H DI0 DI1 CS 16H Data length Control code Identifier of data 7.1.2 Normally response from slave station function: slave station response normally control code: C=81H, no subsequent data frame C=A1H, has subsequent data frame data length: L=02H+m(data length) format of no subsequent data frame: 68H A0 … A5 68H 81H L DI0 DI1 N1 … Nm CS 16H format of has subsequent data frame: Data identifier Data length Control code 68H A0 … A5 68H C1H 01H ERR CS 16H 7.1.3 Salve station response abnormally function: slave station receives wrong request or no corresponding data control code: C=C1H data length: L=01H frame format: Data item
  • 10. 68H A0 … A5 68H C1H 01H ERR CS 16H Note: for error information word, please refer appendix B5. 7.2 Read subsequent data 7.2.1 Request frame from master station function: request reading subsequent data control code: C=02H data length: L=02H frame format: 68H A0 … A5 68H 02H 02H DI0 DI1 CS 16H 7.2.2 Slave station response normally function: subsequent data is transferred according to the format of normal data frame control code: C=82H, no subsequent data frame C=A2H, has subsequent data frame data length: L=02H+m(data length) format of no subsequent data frame : 68H A0 … A5 68H 82H L DI0 DI1 N1 … Nm CS 16H format of has subsequent data frame: 68H A0 … A5 68H A2H L DI0 DI1 N1 … Nm CS 16H 7.2.3 Salve station response abnormally function: slave station receives wrong request or no corresponding data control code: C=C2H data length: L=01H frame format: 68H A0 … A5 68H C2H 01H ERR CS 16H 7.3 Re-read data 7.3.1 Request frame from master station function: request slave station re-transferring the data in last frame control code: C=03H data length: L=00H frame format: 68H A0 … A5 68H 03H 00H CS 16H 7.3.2 Slave station response normally control code: C=83H, no subsequent frame C=A3H, has subsequent frame data length: L=02H+m(data length) Error information word
  • 11. format of no subsequent frame : 68H A0 … A5 68H 83H L DI0 DI1 N1 … Nm CS 16H format of has subsequent frame: 68H A0 … A5 68H A3H L DI0 DI1 N1 … Nm CS 16H 7.3.3 Salve station response abnormally control code: C=C3H data length: L=01H frame format: 68H A0 … A5 68H C3H 01H ERR CS 16H 7.4 Write data 7.4.1 Request frame for writing data function: master station requests slave station to set data(or program) control code: C=04H data length: L=02H+m(data length) frame format: 68H A0 … A5 68H 04H L DI0 DI1 N1 … Nm CS 16H 7.4.2 Slave station response normally function: slave station notify the executing result of the request to master station control code: C=84H data length: L=00H frame format 68H A0 … A5 68H 84H 00H CS 16H 7.4.3 Salve station response abnormally control code: C=C4H data length: L=01H frame format: 68H A0 … A5 68H C4H 01H ERR CS 16H 7.5 Correcting time with broadcast function: make the time of slave station is synchronous with master slave control code: C=08H data length: L=06H data field: YYMMDDhhmmss (year.month.day.hour.minute.second) frame format: 68H 99H … 99H 68H 08H 06H ss mm hh DD MM YY CS 16H 1. It doesn't need response for correcting time with broadcast
  • 12. 2.Only when the time difference between slave station and master station is under ±5min, it executes correcting time command by setting the time of slave station same with that in the command. 3. It doesn't recommend correcting time at 0 clock in case that it will affect some regular operations at 0 clock. 4. It allows correcting time only once every day. 7.6 Write address of device 7.6.1 Request for write address of device function: set address code for some slave station control code: C=0AH address field: 99...99H data length: L=06H data field: A0...A5 (address code of device) frame format 68H 99H … 99H 68H 0AH 06H A0 … A5 CS 16H Note: The request uses broadcast address, which requires the slave station that is set address has corresponding key (switcher) cooperating with the command. The slave station whose key is pressed during the period of master station broadcasting request will response, others will not response. 7.6.2 Slave station response normally function: the device which execute the request correctly responses control code: C=8AH address field: A0...A5 (new address code of the device) data length: L=00H frame format 68H A0 … A5 68H 8AH 00H CS 16H 7.7 change communication speed 7.7.1 request for changing communication speed function: request new communication speed other than 1200bps control code: C=0CH data length: L=01H frame format: 68H A0 … A5 68H 8CH 01H Z CS 16H 7.7.2 salve station response with confirmation Feature word of speed function: slave station confirms the request of changing communication speed control code: C=8CH data length: L=01H
  • 13. frame format: 7.7.3 Slave station deny the request of changing communication speed 68H A0 … A5 68H 8CH 01H Z CS 16H control code: C=8CH data length: L=01H data field: Z=FFH, represent deny frame format: Same with feature word in request speed 68H A0 … A5 68H 8CH 01H FFH CS 16H 7.8 change password 7.8.1 Request for changing password function: change current password of slave station control code:C=0FH data length:L=08H data field: PAoP0oP1oP2oPANP0NP1NP2N frame format: 68H A0 … A5 68H 0FH 08H PAo P0o P1o P2o PAN P0N P1N P2N CS 16H P0oP1oP2o is original password or password with higher authority. PAo represent authority of the password; P0NP1NP2N represents new password or password that need be set. PAN is the authority of new password. The data range of PAo,PAN is 0~9 which 0 is the highest authority. The number is larger while the authority is lower. The level of authority is divided into highest, programming and clear max demand. 7.8.2 Slave station response normally function: slave station notify changing password correctly control code: C=8FH data length: L=04H data field: authority of password and password PANP0NP1NP2N frame format: 68H A0 … A5 68H 8FH 04H PAN P0N P1N P2N CS 16H 7.8.3 slave station doesn't response when it go wrong 7.9 Clear max demand 7.9.1 request for clearing max demand function: for tariff device which is working on non-automatically meter reading mode, the command can implement clearing max demand and data rolling of energy in current month, last month, the month before last month and register of max demand. Control code:C=10H data length: L=00H frame format: 68H A0 … A5 68H 10H 00H CS 16H