jconder
Member
I have configured a Micrologix 1100 as Modbus RTU slave but it won't respond to any request for holding register data. I have a very simple program running that copies the data from an attached RTD I/O module into file N9 (which is mapped to Modbus address 4XXXX). Using default comm interface and RSLogix software, I can see the PLC program running - the registers are updated with temperature information, but when the unit is returned to the "as programmed" run state, it never responds to Modbus requests. The Modbus configuration is 9600, 8, n, 1, no handshaking, and the node address is 1. I'm using the 1763-NC01 interface cable. What am I missing?