Modbus RTU Annex points do not operate correctly with the special function codes

Issue

When using a Modbus RTU block reads with a special function code incorrect data can be seen.

Product Line

Andover Continuum

Environment

Modbus RTU X Driver

All controller types that support X Drivers

Cause

The Modbus RTU X Driver does not support the use of block reads (annex points) for the special function codes.

Resolution

The Modbus RTU XDriver supports special function codes to convert various (Non Modbus standard) data formats for use in Continuum points.

As detailed in the Modbus RTU X Driver manual (Param6) function codes, Parameter 6 should not be entered for Function codes 241 to 254.

A separate X Driver point is required for each value to be read when using a special function code.