The setup is a CPM2A & NS5.

I have an alarm configured to switch screen when alarm/event
happens. The setup is a CPM2A & NS5.

2 things were not quite right. The first was, if the alarm
condition was active, then the screen would be displayed
permanently, the operator could not exit from the screen until
the alarm condition is cleared.

What I then tried, was using a 1-shot to an internal address
so that the screen could be exited if required. This did not
work, the screen did not switch when the alarm condition was
active? I was using the LR area for this, should not be an
issue, as they work fine when the 1-shot is not used.

This seemed odd to me, what I had to do in the end, was to use
the $SW allocation & screen switch function. I then 1-shot
the required screen no based on the fault condition.


So the problem is 2-fold,
1. If alarm is configured to switch to a specified screen, it
will keep switching to that screen until the alarm is cleared,
I am ok with this, as could act as a sort of security feature as well.
2. When the alarm is configured to trigger a 1-shot, the NS-Screen
does not recognise the change of state.

Hi Scott
I wouldn't expect the comms to detect a oneshot.

What I do is put an Acknowledge PB on the Alarm popup screen. I use this to copy the current alarms (W10, say), to the Acknowledged Alarms (W20, say)

So if W10.0 is on, after ACK, then W20.0 is on. I use this flag to unlatch the alarm condition, thus.



This leaves the alarm acknowledged until the alarm trigger clear i.e. you don't keep having to press 'reset'.

At the end of the alarm capture code, AND W10 with W20 and put result in W20 - this clears the ACK bit after the alarm has cleared.

If W10<>W20, then you can show the alarm page.

Pp

Thanks for your reply PP



How come, my understanding, is that the 1-shot is on for 1-scan, and the peripheral
servicing is done at the beginning of each scan. The 1-shot bit should be recognised
as being on at this stage?



So you use a popup sceen, these screens are only NS5's, and have been imported from previous
NT versions. This could be done, but the screen would stay active, due to the 'trigger' bit still
being on.



So you have an automatic reset, if the alarm has been acknowledged?



I have done this also on other projects, this one is a customer that has done the screens
on their own, as with most projects, improvements could be made...

Hi Scott

Regarding the oneshot, I don't know enough about the comms servicing. Which comms format are you using? NT Link or Hostlink? Hostlink won't, NT Link may; my understanding is the PLC initialtes comms. Correct?

I only show the blank alarm popup when the Alarm word doesn't equal the acknowledge word i.e. when a new alarm appears. The individual alarm bit populates the alarm display object.

I feel once the alarm is acknowledged, then it's ready to be reset when the alarm trigger clears, kind of 'automatic', as you say.

Any use?