Rung Limits

I'm using RSLogix 500 to modify some programs on various equipment in our facility. I have a question: Can anyone tell me if there is a limit to the number of instructions you can use on one (1) rung in series. I'm currently using 20 XIO bits in series as conditions before the output on my rung. I'd like to add 15 more XIO bits in series on this same rung. How many more of these can I add in series on this rung? Does RSLogix have a limit? I understand that my processor should be configured to hold the size of the program file itself so I'll make sure my program size doesn't exceed what the processor can hold. But is there a specific limit to the number of instructions one can use in series on a certain rung or is it basically infinite. I attached an image of the rung I'm wanting to add more instructions to. I appreciate the help. Thanks.

I can't remember the limit but I'm pretty sure you'll hit it trying to add 15 more XIO on the same rung. The way around it is to have a row of XIO to make an internal bit, then use that internal bit as the first "input" of the next rung followed by more of the necessary XIO bits. One thing I do is group the XIO into logical groups making internal bits, then a rung of the internal bits all together. For example
XIO I:1/0 XIO I:1/1 XIO I:1/2 XIO I:1/3 (OTE)B3:1
XIO I:1/4 XIO I:1/5 XIO I:1/6 XIO I:1/7 (OTE)B3/2
XIO B3:1 XIO B3:2 (OTE)B3:3

I have seen 50 instructions in a PLC5 program. I don't think there is a limit. Try it and let us know.

Duranthas reply is golden.

Please heed this.

Think of the next guy.

ganutenator said:

Duranthas reply is golden.

Please heed this.

Think of the next guy.

Click to expand...

Yes but, the question was not to do or not to do it was are there limits.
Sorry, I could not resist.

128 is the limit.

OG

I would use the grouping with internal bits also, much easier to read. If your bits are sequential you could use word compares as well. If the word equals zero,then all bits are off. Just a thought

I would agree with Ken and look at the word from the cards as compares. It would lead to alot cleaner more condensed looking rung.

If you are bent on using chained bits to accomplish this you can do as Duranthas pointed out and somewhat group them on seperate rungs.

The key is to make it easy to understand and well labeled. It can save you a 3am call just to point out a simple fix.

Thanks gentlemen. A lot of good suggestions. The grouping suggestion was one alternative I already knew of. But I did not think of the word comparison idea using sequential bits. That was a good idea as well (thanks Ken). But as Mickey said, I was just asking the original question out of curiosity. But all the suggestions and comments are very helpful to me or who ever else can be helped by reading these posts. This forum is a great help. Thank again guys! God Bless!

Behold! The pain of 127 inputs and the output

I have never seen a case where so many inputs were needed to control one output. This looks like a case where some rethinking of the Panelview control program may be needed. Surely there is a more efficient method.

As we say down here in a local expression, Eisshhh!

Duranthas said:

Behold! The pain of 127 inputs and the output

Click to expand...

And a partridge in a pear tree!