Applies To:
  • CitectSCADA

The deadband argument in ctListAddEx does work as designed.
See Bug 42100

When testing this make sure ModSim32 to set the tag values.  Deadbands do not apply to values set by the client (e.g. Tag debug) or using Ctapi.

The deadband only applies to information coming from a PLC.  It does not apply to information set by the operator through the client or through ctapi.

PLC <-> IOServer <-> Client/Ctapi subscription

Starting with tag1 on PLC being 0 ...

If tag1 on the PLC is changed to 1, there is no update of the value of tag1 held by IOServer due to subscription deadband.
If tag1 on the PLC is changed to 100, the value held by IOServer for tag1 is updated to 100 (because the deadband is exceeded).

If tag1 is set to "X" by an operator using a client or ctapi => the value of tag1 held by the IOServer and the PLC is set to "X" regardless of any deadband setting.  The value of "X" for tag1 will be then be passed to all other clients and ctapi subscriptions.


ctapi, deadband, ctListAddEx, subscription, IOServer