Accuthermo Technology Corp.
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communication agent between PC and controllers. The software supplied by Accuthermo cannot
talk to multiple controllers; only one at a time with proper ID address selected.
4.1.2 Communication Protocol Format
RS232/ RS485-Modbus RTU
Party
None
Data bit
8 Bit
Stop bit
1 Bit
Baud rate
19200 bps
CRC16
YES
4.1.3 Communication Read/Write Format
Read Command Code: hex x03
Write Command Code:
hex x06
Each time a command is sent from the master (ex. Computer) to the controller, the controller
receives should immediately response a similar message back to its master. For example:
SEND:
The PC send a command set (total of 8 bytes) asking for the temperature that was just
measured: x01-03-1000-0001-CCCC
RETURN:
The slave unit (controller) returned an 8-bytes data to its master:
x01-03-0002-01F7-CCCC. Where “x01F7” is the temperature measured in Hex format (=50.3
℃
);
where “x” means hex format, “C” means CRC data.
1
2
3
4
5
6
7
8
Represent
ID
R/W Function
Parameter Address
or Byte count
Data Cnt
Or Rtn
CRC
Byte Count
1
1 bytes
2 bytes
2 bytes
2 bytes
Byte 1 – ID: It is the ID number of the controller, the default is 1.
Byte 2 – R/W Function: Read function is hex number x03, Write function is hex number x06
Byte 3,4 – Parameter Address or Return Byte Count: See the following example and description
for detail.
Byte 5,6 – Data/Data Count/Data Return Count. The 2 bytes have different meanings during the
read-send/return. For write process, the send return should have the same value.
Byte 7,8 – Modbus CRC: 16bits Cyclic Redundancy Check is done to prevent corrupted data
during communication transmission. It takes the first known command bytes through a
CRC calculation and generates the 2-CRC bytes at the end.