Strange behavior of RSLogix CPT instruction

[kolyur]

I was pleasantly surprised to learn that the Micrologix 1400 has the Compute (CPT) instruction available. But my problem is this: The two instructions in the screenshot have mathematically identical expressions, however the first one compiles and the second one doesn't. The second one produces a "Operand sizes don't match" error. Any ideas?

 

[jkerekes]

It looks like your second instuction doesn't have enough ")".

 

[Peter Nachtwey]

jkerekes is right, but the error message is wrong and is misleading.

 

[kolyur]

Both expressions have three left and three right parentheses.

 

[jkerekes]

Your right, I can't count!

 

[Peter Nachtwey]

Didn't the one on the bottom.
It looks like you found a real bug then.

 

[DamianInRochester]

I entered the instructions exactly how you have them above, and both of them compiled just fine.

 

[kolyur]

Interesting... were you configured for a Micro 1400 series B?

I don't have RSLogix in front of me right now but I'll mess around with it again tomorrow.

 

[Peter Nachtwey]

Kolyur, is your software up to date? If this is a bug it may be fixed in later versions of the software.

 

[Mickey]

I entered the instructions exactly how you have them above, and both of them compiled just fine.

I just tried it same results, no errors. Using Ver 8.40 RSLogix500.

 

[DamianInRochester]

I was pleasantly surprised to learn that the Micrologix 1400 has the Compute (CPT) instruction available. But my problem is this: The two instructions in the screenshot have mathematically identical expressions, however the first one compiles and the second one doesn't. The second one produces a "Operand sizes don't match" error. Any ideas?

Interesting... were you configured for a Micro 1400 series B?

I don't have RSLogix in front of me right now but I'll mess around with it again tomorrow.

I'm using 8.10.00 (CPR 9) which only allows me to select an ML1400 series A. How large is you L10 data file?

 

[DamianInRochester]

The reason ask about the size of the data file is I can get the same error "Operand sizes don't match" if I fail to make the data file large enough to include the elements you use in your ladder.

 

[DamianInRochester]

OK, now oddly enough I am now able to duplicate your error. If I do a verify project it now rejects that CPT block.

 

[DamianInRochester]

It appears to be some sort of nesting limit.

If I enter
( ( L9:1 * 10 ) * 10 )

it is fine, but if you do another
( ( L9:1 * 10 ) * 10 ) * 10

it gives the Operand size error again.

So yeah, it is either a bug or a restriction that appears to be undocumented.

 

[RoTaTech]

Add extra parentheses, perhaps?

What if you tried adding another pair of parentheses around the whole formula?