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
|----- 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
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RE: First pass - OSR
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
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?