I have an old GE LM90-30 PLC which is a spare unit for one of my clients. I am attempting to communicate with it using the serial port located on the PLC rack’s power supply,. This connection works for GE’s Proficy v9.5 PLC programming software.
I have installed the Modbus Serial RTU Gateway module to Ignition and configured the connection, which shows OK in both the Gateway Config page and also PLC Metadata tag “PLC_Is_Connected” returns a value of 1 (good quality).
However, I am unable to read a holding register (GE address %R00003) using the Ignition tag address format [PLC]HR3, as indicated in the latest User Manual Modbus instructions. This tag address returns “null, Bad” status instead.
Does the Ignition Modbus Serial Module adhere to the same Modbus addressing conventions as the Modbus TCP modules?
Bakersfield, CA, USA.