Connecting to GE CPU001 PLC using pilot light and plcaddressvalue

[pk]

Hi
Thanks for a great program and experimenting more with GE CPU001
We have an Alarm monitoring system where we have all discrete inputs to the PLC and are  monitored by an HMI (RS485)
The ladder logic on the PLC have Auxiliary relay coils M00301 to M00350
I finally got my PLC connected through my USB-RS485 adapter 9600,8,None,1, Com2 (ModbusRTUCom1)
On my Mainform have 2 pilot lights with PLCAddressValue - 00334 and 00348 (M00334 and M00338)
When I physically change the inputs the connected HMI value changes while I get Bad Checksum error?
Do I need to change plcaddressaddress 00334 / 00348 to some other address Modbus format?
Just need an pilot light indicator to turn on when there is an input without any major code
Can someone pls explain in layman terms what I am missing
Thanks

[Archie]

I don't know the GE PLCs. Is there a manual that shows the Modbus address translation from GE addresses?

[pk]

Archie
Thanks for the immediate reply
Attached some more info, looks like the M address are not accessible?
Any advise from your end and any help is appreciated
Thanks

[Archie]

Seems that you will have to add to the PLC program to copy the values from the M space to one of the Modbus accessible spaces.