Applies To:
  • CitectSCADA 5.20

I have just upgraded my project from V4.20 to V5.20 and now I get compile errors "Unknown IO Device".  What has changed? 

Citect used to fully support redundant IODevices having different names to the primary IODevices. eg IODev1_P may be configured as Primary and IODev1_S may be configured as Standby_Write. As long as the two devices had the same IODevice Number this was accepted.  In Citect V5.20 this is still supported.  However, if you then reference the standby device, eg in a variable tag form, you will get a compile error "Unknown IO Device".

To overcome this change in V5.20, modify your variable tags database to reference primary IO Devices only.  This makes no difference to IO communications as Citect will always communicate to the Primary device anyway, unless a coms failure occurs on that device.