Applies To:
  • CitectSCADA 3.xx, 4.xx, 5.xx

When connected to a device using the SNP protocol, and under a timeout condition which recovers (a temporary coms failure) a "Driver Not Responding" error may occur.  On checking the driver parameters it was found that (Retry + 1) * Timeout (seconds) < Watchtime, as required in Citect versions prior to Citect 5.21 Service Pack B. 

CIT has confirmed this to be a problem in the SNP driver.  It has been found that the SNP driver should have a MaxPending parameter value of 1.  This problem has been fixed in SNP driver version 2.2.  The change has been to modify the default value of MaxPending to be 1.