Sorry for the delay in my reply.
Yes, we could add this kind of functionality to the diagram.
There are several concerns though. We should consider these
issues before deciding what to do:
1. We do not want to FORCE writability of Interface_Value.
Yes, if you want to implement this in your product, then OK
it should work the way you described (maybe). This implies
to me another parallel switch based on Out_Of_Service
where Writes to Interface_Value are routed to nothing
when Out_Of_Service is false and to Interface_Value when
Out_Of_Service is true.
2. I am not sure that Interface_Value is necessarily writable
ALWAYS under these conditions. I think it is subject to
the Override Decision. In that case, the bucket we show
as Last In-Service Value is really the thing that gets
written if you write to Interface_Value, but the actual output
may be a manual setting if it's overridden. This depends on
how override is implemented in the device, and BACnet doesn't
Can you describe the use case where an output is Out_Of_Service=true
but you still need to change the physical output?
914 South Aiken Ave
Pittsburgh PA 15232-2212
From: Christoph Zeller [mailto:christoph.zeller@...
Sent: Thursday, November 29, 2007 7:57 AM
Subject: [bacnet] proposal dmf-036
I was looking for your propsal DMF-036.
Thanks for pointing out the behaviour of out-of-service and the
In figure I-2 you show the behviour of an output object.
I would suggest to add an additional path for writing to interface value.
Reason, If an output is set to out of service, there is no way to set the
physical output using bacnet services.
Once in OUT-OF-SERVICE mode, the interface value will not move anymore.
If we would add the same service as in the input objects "writes to
interface value" to the left and connect this with
the true path that disables the connection from present value. We could
stick to the behaviour but savely park the
physical output in the desired position.
I would offer to add the modifications in the graphics if desired to do
so. Unfortunately I cannot edit the graphics
in the proposal.
What do you think about this modification?
Best regards Christoph
Fr. Sauter AG
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