Slc500

aldy · Mar 14, 2013

Hi to all Mentors and Master, I am newly member and newbie for the PLC system, I just want to explore more things about technique and uses.

Can anybody explain to me..

1. S:1/15 (First Pass).
2. What is the purpose of the S:1/15 (First Pass).
3. Can someone give me sample.

Thanks a lot.

AL..

Anirban Hazra · Mar 14, 2013

The First Pass Bit being set indicates that the First Scan of the user program is in progress.That is, it is high when you put the controller into "Run" mode and it scans your program for the first time. It can be utilized in programs where you wan to initialize certain values,parameters,etc in the first scan itself.

aldy · Mar 14, 2013

is that so, it means if i will put the (first pass bit or S:1/15) in the rung 5, it will activate automatically the rung 5 in the 1st cycle, is it correct?

Can you give me some sample?

Thanks a lot.

habadeer · Mar 14, 2013

In addition to Anirban's explanation, an important thing to note is that the bit will stay high (or on) for only one scan (the first scan). As Anirban said, it is used to initialize things, unlatch bits, move starting values into registers, reset retentive timers, maybe even run a whole initialization routine via a JSR instruction.

TConnolly · Mar 14, 2013

Here is an example. Lets say that I have a bunch of operating parameters and I want them to initialize to default values whenever the machine is powered up. I'll put the code to initialize everything is a subroutine (ladder 10 shown below) and call that subroutine on the first scan.



  S:1/15

---] [--------------------+-JSR-----------------+-

                          |SBR File Number  U:10| 

                          +---------------------+

Lancie1 · Mar 14, 2013

If there are only a few bits that need to be set in the first PLC scan after switching from PROGRAM to RUN mode, then you can set them directly in parallel rung branches.

Slc500

aldy

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Anirban Hazra

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aldy

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habadeer

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TConnolly

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Lancie1

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