RSLogix 500 EQU

chuckiebuckets · May 17, 2019

I want to compare an integer with multiple constants. Can I use just one EQU command for this or do I have to use a seperate EQU with each comparison? Such as, N7:0 can be equal to 1 and 4 and 5 and so on...

Steve Bailey · May 17, 2019

If the values you want to compare the source integer to are consecutive you can use the LIM instruction. Otherwise you will need to test each condition. You can parallel the EQU instructions to keep it on a single rung.

chuckiebuckets · May 17, 2019

No, they are not consecutive. I have 15 different comparisons for one true statement. The rung will be very long with that many branches. But I can do that if that's the only way. Thanks so much for replying.

geniusintraining · May 17, 2019

How often are you needing to compare? you could use a MOV and move the constants to the EQU run the cycle then move another constant to the EQU? not sure what would be better

Steve Bailey · May 17, 2019

The rung will be very long with that many branches. But I can do that if that's the only way.

You don't have to put all of the EQU instructions on one rung. But you will need to use an OTE instruction to keep track of the results of each rung of comparisons and then OR all of those intermediate results.

James Mcquade · May 17, 2019

be careful with the number of parallel branches.
every time I go more than 8, I start having issues with the logic.
you have to read the first published manual. it limits the number of branches to 8 if memory server me correctly.

james

bernie_carlton · May 17, 2019

I believe the limits on parallel logic are much higher using extended branches than using nested branches.

chuckiebuckets · May 17, 2019

Ok, understand. Thank you.

JaxGTO · May 17, 2019

bernie_carlton said:
I believe the limits on parallel logic are much higher using extended branches than using nested branches.

Great point!
Also with SLC the Extend branches don't cost any memory but nested branches do, 2 words I believe 1 for open and 1 for close.

cwal61 · May 17, 2019

What are the 15 numbers? Depending on the number sequence you could combine LIM and NEQ to cover a range of numbers like Steve suggested. Like 1, 4 & 5 could be coded.

LIM 1-5 and NEQ 2 and NEQ 3.

chuckiebuckets · May 20, 2019

Here's the numbers: 0, 2, 3, 4, 7, 9, 18, 19, 20, 21, 22, 23, 24, 29, 36

chuckiebuckets · May 20, 2019

OK, this makes sense. Instead of 15 branches, I can cut it down to 7 branches using the LIM statement. Thank you so much for all of your help.

cwal61 · May 20, 2019

4 branches

LIM 0-9 and NEQ 1 and NEQ 5 and NEQ 6 and NEQ 8

LIM 18-24

EQU 29

EQU 36

chuckiebuckets · May 20, 2019

Thank you cwal61. That's great! I think I am finally getting it. I really appreciate this forum.

RSLogix 500 EQU

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