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

When using the APPLIC driver with redundant Citect I/O devices configured, a problem can occur when disconnecting the primary I/O device. It is found that the standby device may go offline as well. What is the solution to this problem? 

A likely source of the problem is that the timeout configured in the Applicom software is greater than the Citect driver timeout, causing the Citect driver to timeout before the lower level Applicom layer. This is undesirable and may cause communication problems with the secondary I/O device.

It is often possible to make the timeout of the Applicom layer smaller by reducing this parameter through the Applicom software. You should make this timeout smaller than the Citect timeout; set it to around 1 - 2 seconds if possible. The Citect driver timeout parameter should also be fairly large. The default timeout for version 2.08 of the APPLIC driver is 5000ms. This could even be extended further if required.

To make the driver timeout to be 8000ms, make the following setting in the citect.ini file:

[APPLIC] TimeOut=8000