Technical Forum

STEP 7 (TIA Portal)

self starting timer

Thread Starter: ATMega128 Started: 8/19/2012 9:16 AM Replies: 2

8/19/2012, 9:16 AM

ATMega128

Joined 3/13/2007

Last visit: 5/13/2013

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hi folks,

I'm new to SCL and having the following question : why isn't this working ?
The idea was to have a 1 cycle pulse each 100 msec ( StartTimer1 inverted)

IF NOT "StartTimer1" THEN "StartTimer1" := true;
END_IF;

"CurrTime" := S_PULSE (T_NO:=1, S:="StartTimer1", TV:=100ms, R:=False, BI=>"TimeRemainTimer1", Q=>"Timer1");

IF NOT "Timer1" AND "StartTimer1" THEN "StartTimer1" := false;
END_IF;

The timer runs once but doesn't restart again !! StartTimer1 has a 0 to 1 transition !?!
Kind Regards

Johan

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8/19/2012, 10:42 AM

fbelic

Joined 2/17/2009

Last visit: 5/21/2013

Posts: 320

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Rated: Excellent [4.28 out of 5 / rated 25 time(s)].

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Greetings

It is not working because timer starts on transition from 0 to 1 (false to true). You would need to make additional one-cycle pause before the first line...

But anyway, there are better ways to do this. You can make OB that periodicaly runs every 100ms. Or use clock memory that changes every 0.1s.

Best regards

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8/19/2012, 8:59 PM

ATMega128

Joined 3/13/2007

Last visit: 5/13/2013

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