The PLC can be programmed to periodically capture ADC data into internal memory which is directly readable by the OIT as a MODBUS holding register.
If the OIT want to change a value of DAC, it has to write the data to another MODBUS holding register address and the PLC will take the data and send it to the DAC by using the SETDAC command.
The digital Inputs and Outputs, internal relays, timers and counters are all directly mapped to the MODBUS holding register address betweeen 40001 and 41000.
