prefailed, prepassed, failed, passed concepts in DEM

[prk1989]

Dear All,
Currently i am studying diagnostic Event Manager(DEM) module and I have gone through concepts called prefailed, prepassed, failed and passed.
As per my understanding prefail is used to count the error occurrence and stored in nonvolatile for the first operation cycle.
In the next operation cycle if the error is not present then the prepass counter used to maintain the status.
But unable to get understanding about the Failed and Passed concepts. Could any please guide for me regarding these concepts?

[vipillai]

I am not familiar with that module. What NI hardware or software are you using with this module?

[prk1989]

Hi,

The question which i'm asking is about the software concept used in one of the diagnostic project. They are the common concept use in automotive domain i guess. If any of our group member knows please explain me.

[vipillai]

I'm not familiar with that software concept, sorry.

[Minions]

This sounds like a software persistence hysteresis. 

Here are the phases.

• <PASS> The unit begins without error (Count = 0)
• <*> Upon seeing an error, it begins to count up by some increment (Count ++i)
• <ERROR> If count meets or exceeds a certain threshold then it will Flag it as an <ERROR> (Count >= T)  The max value of count is then reset to T.
• <*> Upon seeing a pass and the count > 0, it will count down by some decrement with the min of count = 0 (Count --d)
• <PASS> If count equals = 0, then it will Flag it as a <PASS> (Count == 0)

The ones marked with '*' will keep the present Flag State.  It is possible for the Pass, Fail, Fail, Pass, Fail states to continually show a Flag of <PASS>.  It is all dependent on the increment / decrement and count fault threshold.