Trying to Poll Horner RX371 w/modbus

[Benvt]

Sorry, I'm very new at Modbus/TCP & PLCs in general.. I'm trying to poll(and in the end read/write to) a register from a Horner X371 PLC, the register identified through Cscape is %R6208.. Would that register be a normal holding register? (use FC 3 to poll)? ..

I can get to some other registers, but I cannot seem to poll this one.
(writing code in perl MBclient & tried in 'Simply Modbus TCP client')

Thanks,
Ben

 

[Steve Bailey]

That register should be a holding register. If you can read other %R memory, then it could be that the entire %R memory space isn't mapped into Modbus memory space. Is there any Modbus configuration available within CScape?

 

[aclemence]

Hi Ben,

I know it's late, but others may come across this page via Google as well...

The first 2048 %R registers are available via the Read Holding Register command in all firmware versions by the looks of it.

The %R registers up to 9999 should be available in later firmwares using the Read Holding Register command. Note that a Modbus offset of 10000 is required for the registers in this extended range, whereas 3000 is used for the first 2048 Modbus registers.

Thus you should set your Master to read holding register, address 16208.

I use Modbus Poll from Modbustools for all my testing and have had no issues to date.