allen bradley rslogix 5000 vs Siemens S7; Tag initial (power-up) value

rthus · Mar 2, 2010

Hi,

I have started my first Allen Bradley project. I am much more familiar with Siemens S7 PLC's.
For now, just one simple question:
How do I set the initial value for a tag. In other words, how do I specify the value of a tag after power-up. Do I need to write a routine for this, or can I in some way, like with Siemens, specify the initial value for a tag.

Hope you guys can help me out.

Rogier

rdrast · Mar 2, 2010

For any defined tag, if it isn't initialized explicitly, it is retentive. All memory tags on the Logix platform are fully retentive, you don't mark them as you do with Siemens.

To set an initial value, if nothing is writing to the tag, just use the tag browser, and set it there. If you want to make sure that it initializes to a certain value, make an initialization routine, and scan it on "XIC S:FS", which is the first scan bit. In the routine, use MOV instructions to set the values you want.

rthus · Mar 2, 2010

rdrast said:
For any defined tag, if it isn't initialized explicitly, it is retentive. All memory tags on the Logix platform are fully retentive, you don't mark them as you do with Siemens.

To set an initial value, if nothing is writing to the tag, just use the tag browser, and set it there. If you want to make sure that it initializes to a certain value, make an initialization routine, and scan it on "XIC S:FS", which is the first scan bit. In the routine, use MOV instructions to set the values you want.

Thanks very much, this was the information I was looking for.

Kind regards,

Rogier

allen bradley rslogix 5000 vs Siemens S7; Tag initial (power-up) value

rthus

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