Applies To:
  • CitectSCADA x.x
Summary:
Citect Device Drivers have standard parameters for changing their operating characteristics. What does the parameter 'Delay' mean? 

Solution:
First, it should be noted that drivers have default values for these parameters. During development the best combination of default values for these values is setup based on our results from testing and our experience with all drivers. We advise that the standard parameter entries are not altered from their defaults unless otherwise advised by Citect support.

The parameter 'Delay' is the period, in milliseconds, to wait between receiving a response and sending the next command. Some devices require delays between handling requests. In some cases devices cannot operate as fast a Citect pushes them to run. This can lead to communications errors or in bad cases the device may fail.

The delay parameter is also important for drivers which would normally return data instantaneously. Front-end/back-end drivers may reply to Citect requests directly from memory. In this case with no delay Citect will request the from the driver needlessly fast (Citect is designed to push communications as fast as possible), this takes computer processor time away from other important tasks and will slow the system down dramatically.

All drivers must provide support for the Delay parameter. For request/ response drivers the parameter should normally default to 0 unless this causes communication errors. For Front-end/Back-end drivers the delay should be 1 which allows other tasks to get some processor time.

 
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