Chapter 8 20 Points RS485 type Models Instruction 211
Modbus RTU slave function
Function Description:
SG2 unit can be controlled by the computer or other controller using the communication control. PC and other
controller can read and write IO state, preset value of the elements and the setting of the unit. It also can use to read
the current value of the element and control the Run/Stop mode of SG2. The maximum frame length in
communication format is 128bytes.
Hardware Configuration:
1. Connect the RS485 port A on each SG2 unit together, also do it to port B, as shown in below figure.
2. Set SG2 in the SET menu to No Remote IO.
3. Set SG2 ID = 01~99.
SG2 Modbus protocol
If SG2 receive a correct frame, it will carry out the command, it responses a correct frame to computer or other
controller. If the command that SG2 received is incorrect, SG2 responses Exception code to computer or controller.
● Command format and Response format
CRC verifying range
Slave address Function code data Data CRC-16
● The Response command format, once SG2 receive an unexpected command.
CRC verifying range
Slave address Function code Exception code CRC-16
Command Format:
Slave address Function code Data CRC-16 Exception code
00H: broadcast to all the drivers 01H Read coils
01H: to the No.01 driver 05H Write single coil
0FH: to the No.15 driver 03H Read registers
10H: to the No.16 driver 06H Write single register
…. 10H Write multiple registers
63H: to the No.99 driver 08H diagnostic
For detail
please refer
register
address
CRC verifying
range contain
Slave Address
Function Code
Exception Code
For detail,
please refer
Exception Code
Instruction
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