To maintain the current value of each mapped CIMPLICITY point within the data address space, the Modbus RTU Slave Interface will accept unsolicited updates (from CIMPLICITY) for all mapped points. Thus, the Modbus master may read values from CIMPLICITY points mapped to any supported memory type (0X, 1X, 3X, and 4X).
However, the Modbus RTU Slave Interface will only attempt to write to CIMPLICITY points that are mapped to data addresses of memory type 0X or 4X. Thus, the Modbus master may write values to CIMPLICITY points mapped to data addresses of memory type 0X or 4X.
Note that for a Modbus master write request to succeed, all data addresses specified must be valid and all corresponding values must be written successfully to PTMAP.
IMPORTANT: When a source point that is mapped to a register number (e.g. 40001) in the mrtusi_rp.cfg file becomes unavailable, the Modbus RTU slave will continue to send the last valid value to a Modbus master that requests a poll for this point.
For example: If the source point (40001) has a value of 12, and a Modbus master polls register 40001, it will receive a value of 12. If the source point then becomes unavailable, any subsequent polls reading register 40001 will receive a value of 12 until the source point becomes available again and the value is updated.
Expected Modbus RTU Slave runtime behavior.