Applies To:
  • CitectSCADA 4.xx, 5.xx

The MODBUS driver does a cyclic redundancy check (CRC) on incoming data and provides a CRC remainder in outgoing data blocks. In some limited cases, such as the testing of "slave" drivers, it may be necessary to disable this CRC. 

From MODBUS driver version 2.02 the following Citect.INI parameter may be used.


Where X is 1 to enable the CRC (the default) or 0 to disable the CRC.

In the case where the CRC is disabled the CRC field in the data transmitted by the driver is 0.

It must be stressed that under most circumstances CRC testing should be enabled. If CRC testing is disabled Citect will be unable to detect communications errors between the driver and I/O devices.