Published: May 25, 2021
OptoMMP server resets when writing to Modbus/TCP holding register(s) with unit ID greater than 1
GRV-EPIC-PR1: All versions prior to 3.2.0 GRV-R7-MM1001-10: All versions prior to 3.2.0
Resolved In Version:
GRV-EPIC-PR1: 3.2.0GRV-R7-MM1001-10: 3.2.0
When using Modbus/TCP to write to holding register(s) with Unit ID greater than one on a groov EPIC I/O unit or groov RIO unit, the OptoMMP server will reset. This will cause the groov EPIC I/O unit or groov RIO unit to temporarily go offline. It will recover automatically.
Use a unit ID of 1 and determine the appropriate starting holding register number using the information under the HOLDING REGISTERS topic in Chapter 3 of the Modbus/TCP Protocol Guide (form 1678).
Or you can use a unit ID of 1 and calculate the appropriate starting holding register number by using this formula:
register_address = 1031 + <slot_number>*(64*2) + <channel_number>, where:
- slot_number is the slot number on the groov EPIC chassis (remember that the numbering begins with 0).
- channel_number is the channel number on the module (remember that the numbering begins with 0).
For example, to set the analog output value for channel 0 on the module in slot 2, write 2 holding registers starting at address 1031 + 2*64*2 + 0 = 1287.
Opto 22 has resolved this issue.
Contact: Opto 22 Product Support.
Phone: 800-835-6786 or 951-695-3080
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