RobotArm (Customer) asked a question.
I am trying to do very simple thing which is to write a value to PLC modbus address.
Technical support said that they use Modbus Poll, so I used the same software. I set the byte to be modbus communication.
I can have my Modbus poll read my PLC data, but I cannot set values using Modbus poll
See my screen recorded video
Hi RobotArm,
Modbus uses 16-Bit references on registers.
You have 32 bit registers set up to change.
C1 - 32 bit integer - Modbus address 400001 and 400002
C2 - 32 bit integer - Modbus address 400003 and 400003
C3 - 32 bit integer - Modbus address 400005 and 400006
If you want to write to C2 then use the following:
Address: 3 - Start of the Modbus address
Quantity: 2 - (2 16-bit registers)
Type: UINT32 Little-endian byte swap - This will set 32 bits in the register.
I hope this helps you out.
Regards,
Garry
You seem to be reading from slave id 1, but are trying to write to id 55? Set ID to 1 in the write. Are you trying to write to tagname C2? That looks to be setup as 32bit DINT and taking addresses 40003,40004.
Hi RobotArm,
Modbus uses 16-Bit references on registers.
You have 32 bit registers set up to change.
C1 - 32 bit integer - Modbus address 400001 and 400002
C2 - 32 bit integer - Modbus address 400003 and 400003
C3 - 32 bit integer - Modbus address 400005 and 400006
If you want to write to C2 then use the following:
Address: 3 - Start of the Modbus address
Quantity: 2 - (2 16-bit registers)
Type: UINT32 Little-endian byte swap - This will set 32 bits in the register.
I hope this helps you out.
Regards,
Garry
https://accautomation.ca/series/productivity-1000-plc/