ABB A43

Communication with Modbus
2CMC48001M0201 101 A43/A44
Revision: C User Manual
Request frame
Example of
a request
A request frame has the following structure:
Slave Address
Function Code
Address
No. of Registers
Error Check
The following is an example of a request. (read total energy import, etc...)
Slave address
0x01
Function code
0x03
Start address, high byte
0x50
Start address, low byte
0x00
No. of registers, high byte
0x00
No. of registers, low byte
0x18
Error check (CRC), high byte
0x54
Error check (CRC), low byte
0xC0
Response frame
Example of
a response
A response frame has the following structure:
Slave Address
Function Code
Byte Count
Register Values
Error Check
The following is an example of a response:
Slave address
0x01
Function code
0x03
Byte count
0x30
Value of register 0x5000, high byte
0x00
Value of register 0x5000, low byte
0x15
...
Value of register 0x5017, high byte
0xFF
Value of register 0x5017, low byte
0xFF
Error check (CRC), high byte
0xXX
Error check (CRC), low byte
0xXX
In this example, the slave with the Modbus address 1 responds to a read
request. The number of data bytes is 0x30. The first register (0x5000) has the
value 0x0015 and the last (0x5017) has the value 0xFFFF