Applies To:
  • CitectSCADA x.x

What are the clock resolutions for the different Windows operating systems and how do they affect Citect. 

With Windows 3.x the clock resolution is 55ms. With Windows NT the default clock resolution is 10ms. With Citect Version 5.20 and later the clock resolution on Windows NT is adjusted to be 1ms.

The following items are affected:

  1. SleepMS() cicode function. The resolution of the SleepMS cicode function will be affected by the operating systems clock resolution.
  2. Certain drivers. These include the SQDIRECT driver. The SQDIRECT driver must respond, according to the protocol, within 10mS of receiving a message making Windows 95 or Windows NT (with Citect Version 5.20 or greater) the most likely operating system capable of handling this driver and protocol.

There may be other specific items affected not listed here. This KB will be updated as needed with any additional items found to be affected.