Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 1.20, 2.00, 2.01

With the KF Protocol, writing to several bits at the same time in the same word was not reliable.

The AB DH-485 Command Set for the SLC500 series provides no method of writing to individual bits. To provide this functionality, the KF driver reads a word from the PLC, modifies a single bit as required, and then writes it back. The driver has bug where writing to bits in the same word is not reliable.  

To work around this problem, put the CITECT.INI setting MaxPending=1 under the [KF] section. The problem has been fixed and will be released in the next version after version 1.20 and 2.01. If you require this fix now, contact Citect Support.