Response time between LabVIEW w/DSC module and RSLinx OPC server hosting FlexLogix PLC tags too long

[sherries]

We are experiencing communication response time delays between LabVIEW with DSC module and RsLinx OPC Server hosting all FlexLogix PLC tags (around 500-600 tags).

1. The nominal response time for the system watchdog is < 500ms, but we occasionally have spikes of up to 1.5 seconds once every few days even when the system is idling.
2. Changing more than six PLC connected shared variables at the same time from LabVIEW also causes the watchdog response times to spike above 500ms.

Our watchdog is programmed so that LabVIEW toggles the watchdog bit to 1 as soon the shared variable event detects that the PLC has toggled it to 0. The PLC, however, waits 300 ms until it toggles it.

Our system:
Windows XP SP3
LabVIEW 9 F3
RSLinx Opc Server v2.54
Allen Bradley FlexLogix PLC

[Hueter]

I have a few questions

What Bus are you using, Serial or Ethernet?

What do you have the update rate set to?

Are you only reading tags?

What is the desiered behavior and what problem is this delay casuing? Are you missing data or locking up your system?

[Ben]

What is your update rate set for in the RSLink OPC server?

You aren't toggling the same flag from both ends are you?

Ben