How to deal with instructions in in-active ladder

AB2005 · Jan 25, 2009

Dears;

I have been working for programming in RS Logix 500 for a corrugator machine. There are some periodic functions in machine which I have programmed in a separate ladder and control with JSR instruction when needed. Now my problem is that whenever JSR instruction would go false, the bits, outputs etc in that specific ladder would remain true if they were true during system last scan while they must be false as they have been using in the other part of program. I am not sure what to do for overcoming on this problem. One solution is that I write those instructions in main ladder and when JSR instruction goes false, system set them zero but they are a large number of.

Please help me out.

panic mode · Jan 25, 2009

you could change program in different ways, for example:
- use FLL to clear range of memory or
- remove conditions in front JSR

BryanR · Jan 26, 2009

You could look into the MCR instruction. This defines a section of code to be executed dependant on conditions, and when the conditions are false, all non-latched coils will be set to off.

OkiePC · Jan 26, 2009

Your best option will probably be to remove (cut) the instructions that condition the JSR and paste them on each of the rungs within the JSR. Then, your JSR becomes unconditional, so the outputs it affects are always updated accordingly.

Conditional subroutines have their place in RSLogix, but it sounds like you chose a usage that does not quite fit.

AB2005 · Jan 26, 2009

Dear Mr. OkiePC

OK, it means there is no way only as you instructed. But scanning the subroutine continuously increases the overall scan time.
Now I have been thinking to remove the conditions before JSR, scan it continuously. Any other instruction?

Thanks in advance.

dougrb · Jan 26, 2009

Setup a bit that fires on the falling edge of the conditions that call the subroutine. Use that bit to call the subroutine one more time, and during that scan, turn off everything you need using the same bit.

daba · Jan 26, 2009

dougrb said:
Setup a bit that fires on the falling edge of the conditions that call the subroutine. Use that bit to call the subroutine one more time, and during that scan, turn off everything you need using the same bit.

Would also be my solution - simple and effective

How to deal with instructions in in-active ladder

AB2005

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