startingAddress (Modbus start address in the slave): Specifies the start address of the data that is accessed in the Modbus slave.
The Modbus_Master instruction uses the MODE input instead of a function code input. The combination of MODE and startingAddress specifies the function code that is used in the actual Modbus frame. The table below shows how the MODE parameter, the Modbus function code and the Modbus address range in startingAddress are related.