IAC Controller to Controller Communication Interval Time
The default IAC Interval Time for Very fast parameter is 500ms. This Interval Time (Very Fast) is editable in AC800M controller IAC settings.
The Customer is expecting a time critical output within 200ms. But the Input signals and Output Signal expected are in different controllers.
Can we configure this parameter to 50ms or 100ms? What would be the expected behaviour of Controller Load or Control Network?, would it harm the controller? This is an existing running plant.
We have an another option (GOOSE), but wanted to check with IAC since its very easy to implement.
Source: PM891
Destination: PM866
The Customer is expecting a time critical output within 200ms. But the Input signals and Output Signal expected are in different controllers.
Can we configure this parameter to 50ms or 100ms? What would be the expected behaviour of Controller Load or Control Network?, would it harm the controller? This is an existing running plant.
We have an another option (GOOSE), but wanted to check with IAC since its very easy to implement.
Source: PM891
Destination: PM866
Asked 1 month ago
Answers
1
I think IAC will work in 100ms cycle.
A long time ago I was testing how fast is a MMS exchange rate between 2 AC800M controllers. I found 50ms is a more-less stabile cycle time.
IAC is more effiecient than MMS , so IAC should work reliably at 100ms cycle.
According to experience, IAC communication can be interrupted during downloading newly created communication variables. Controllers are being downloaded one by one therefore there will be a gap in the communication.
I think this issue can be fixed by holding registers at recieving side of IAC , which hold last valid data if Comm.var:Status is not equal to 16#C0 .
Regarding Control network, it can be affected. It depends on the real traffic , how much OPC is loading both controllers . Check MMS traffic in controllers.
If this is a communication involved in a critical process , rather consider using DPDP Coupler at Profibus or Profinet.
A long time ago I was testing how fast is a MMS exchange rate between 2 AC800M controllers. I found 50ms is a more-less stabile cycle time.
IAC is more effiecient than MMS , so IAC should work reliably at 100ms cycle.
According to experience, IAC communication can be interrupted during downloading newly created communication variables. Controllers are being downloaded one by one therefore there will be a gap in the communication.
I think this issue can be fixed by holding registers at recieving side of IAC , which hold last valid data if Comm.var:Status is not equal to 16#C0 .
Regarding Control network, it can be affected. It depends on the real traffic , how much OPC is loading both controllers . Check MMS traffic in controllers.
If this is a communication involved in a critical process , rather consider using DPDP Coupler at Profibus or Profinet.
Answered 1 month ago
1
> The Customer is expecting a time critical output within 200ms. But the Input signals and Output Signal expected are in different controllers.
That's your fundamental problem and its a ~ bad idea ~ . Rather than try to fix this with a software "bodge" that relies on a ( potentially ) variable and relatively slow communications link, install a cable or a bus extension and wire it correctly.
That's your fundamental problem and its a ~ bad idea ~ . Rather than try to fix this with a software "bodge" that relies on a ( potentially ) variable and relatively slow communications link, install a cable or a bus extension and wire it correctly.
Answered 1 month ago
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