×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

First pass - OSR

First pass - OSR

First pass - OSR

(OP)
I am trying to understand and will be cleaning up a AB ladder logic program. The first rung has;

|----- NOT S:1/15 ------- OSR B3:0/0 -------------------------- ( B3:0/1) --------|

B3:0/1 then turns B3:0/2 on and holds itself on with a branch around B3:0/1

Most, if not all, rungs are then only true if B3:0/2 is on.

1) What is S:1/15?

2) What advantage is it to set this bit on during the "First Pass" as it's labeled?

Thank you in advance for your help thumbsup

RE: First pass - OSR

S:1/15 is "First Pass", that is first scan pulse.
This is a system read-only bit active only in the first scan after power up or switching from programming to run.
The B3:0/1 in the shown code is "not first scan pulse", that is "the second scan".
If the B3:0/2 is being set by "the second scan" and self-retain, it will mean "not the first scan", which is the same as NOT S:1/15. The goal of such unnatural definition of "not the first scan" cannot be clear without seeing the program.

RE: First pass - OSR

(OP)
Ok, so I looked into it further and found one other use of the B3:0/1. Way down in the program, B3:0/1 is used as one way another bit is unlatched.

So it looks like nothing happens the first scan;
second scan gets the bit unlatched;
and the third scan the whole program is looked at it.

Does that make sense? Am I thinking correctly?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources