Remote panel as well as PLC with modbus - both represents modbus masters.
Modbus communication from its principle does not support two masters.
The best solution to share one slave (ATS) between two masters (PLC and HMI) is to use modbus port multiplexer. This device alternates modbus requests, once between ATS and PLC and second time between HMI and ATS and so on.
See attached files for more info about PXP-314MB port multiplexer.

เผยแพร่สำหรับ:ชไนเดอร์ อิเล็คทริค Thailand