Modbus - Quantum to Phoenix Digital


Thread Starter


Modicon Quantum talking Modbus RTU out of Port 1 to a Phoenix Digital Fiber Module, OCM-MOD.

The issue is the FOM requires handshaking, not typical with Modbus RTU. When I enable RTS/CTS control in the Quantum here's what happens:
Quantum sends RTS - High
FOM send CTS - High

Quantum sends - Data Thru but never drops RTS - Low
The slaves answer but the master FOM never receives it because it is still geared for transmission (due to RTS still being High).

I've tried numerous StartDelays and EndDelays, nothing seems to matter. I'm using Concept 2.6 and programming in Ladder Logic.

How can I get RTS to reset from the Quantum? Help!!