Is this possible with an S7 314?

sparkysliderz

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Join Date
Feb 2005
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Hi Guys,

Is it possible to interrupt program flow to guarantee the capture of an event?

Am I right in saying that OB1 only takes a look at the state of inputs and outputs at the beginning of each scan?

For example. Our PLC cycles at around 13 – 17 msec’s,. does that mean that the inputs and outputs are only "mapped" 13 – 17msec’s?

If we have a retro reflective sensor on an input and the sensor only signals for much less than the scan time of OB1, will the sensor signal ever be missed?

Is there any way of guaranteeing that this event (signal) will not be missed?

 
Is it a 314 or 314IFM? The IFM has got 4 (I think) hardware interrupts which will do exactly as you wish. As Amr says, these can be configured to invoke OB40, where you can react to the sensor.
If it's the 314, then I'm not too sure. Sorry.

Pp
 
You could feed your sensor into a high speed counter card (e.g. ET200S) and then monitor the count in OB1. When the count increases, you know the input has changed from 0 to 1 for example.
 
It is definitely possible with an S7-314, but then you'll need an input card with interupt possibilities, the 6ES7 321-7BH01-0AB0.

Kind regards,
 

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