Why do indirectly referenced string arrays show up as '??' within tag elements?

[asciutto]

Per title, I have an example string array Foo of datatype STRING[10] and index Bar of type DINT

EQU('False',Foo[Bar]) works functionally but on the rung the result of Foo[Bar] is ??

If I do EQU('False',Foo[0]) the result of Foo[0] is 'False'

Is this normal operation for indirectly referencing a string array? I googled high and low and couldn't find a thread that mentions this occurring or what the normal expected behavior is.

Thanks!

 

[dmroeder]

While LogixDesigner will display ?? when indirectly addressing strings, the compare will evaluate properly. Why they cannot resolve and display correctly when it can evaluate correctly is beyond me.

There is a technote that claims the reason it won't resolve and display correctly has to do with the fact that a string is made up of .LEN and .DATA[], it doesn't know which to display when indirectly addressing. I find this reasoning complete nonsense. If it can display a non-indirectly addressed string fine, it can display an indirectly addressed one. It knows not to display .LEN or .DATA[] because they are not included in the syntax.

Edit: KB QA50171

 

[asciutto]

Wonderful, thank you for the insightful response!

I suppose a viable workaround is to have a 'Result' string and move the indirectly referenced string into it if visibility from the rungs is important

 

[dmroeder]

Wonderful, thank you for the insightful response!

I suppose a viable workaround is to have a 'Result' string and move the indirectly referenced string into it if visibility from the rungs is important

Yeah, if you really wanted to visually see the the result on the rung, which I get, then copying it to a new string would do the trick. It wouldn't functionally offer anything, but it would look better.

A while back, I was working on a ladder viewer written in python and Qt. I was able to correctly display string values that were indirectly addressed, not sure why they can't.

 

[kwade]

A while back, I was working on a ladder viewer written in python and Qt. I was able to correctly display string values that were indirectly addressed, not sure why they can't.

They RS/AB are probably waiting to see if there is significant industry IRE, then release a PAID update to resolve the issue.

 

[dmroeder]

They RS/AB are probably waiting to see if there is significant industry IRE, then release a PAID update to resolve the issue.

Puh-lease. You don't really believe that.

Any minute now, after 20 years of releases, we're going to hit critical mass on our string indirect address resolution "issue", then we can hit them in the pocket book for the fix

It's not a big enough "issue" to make the list, so it get chucked into the "works as intended" bucket. It's not some money making conspiracy.

 

[kwade]

Puh-lease. You don't really believe that.

Buh-lieve that they would? Not really.
Suh-prised if they did? Again, not really.

Sarcasm/hyperbole do not come across well in a text environment.
I have used AB and RS (since ICOM AP/APS) long enough to understand that AB/RS rarely pass up an opportunity to squeeze an account.

Early 2000's, my local MCMC account manager (or whatever title is appropriate) informed me that AB/RS was changing the techconnect support scheme from number of software packages under support to the number of programmable devices under support.

This change would increase my support contract price from (approx) USD 2,000/yr to (approx) USD 22,000/yr.
I balked and said that I would cancel all support contracts because the only support that we required was software updates.
The MCMC response was that we would be allowed to continue to pay our usual USD 2,000/yr.

If this is not the AR/RS milking arm in operation, nothing is.

It's not a big enough "issue" to make the list, so it get chucked into the "works as intended" bucket. It's not some money making conspiracy.

Does any other software have 'totally unplayable' issues with MS Sans Serif?
I have experienced a few AB/RS issues with someodd OS/environment settings/peculiarities. It *almost* appears that AB/RS devs seek out these oddities and implement *features* that either exploit them or require them for operation.
You devised a 'workaround' for one of them! 1747-UIC drivers?

 

[dmroeder]

Buh-lieve that they would? Not really.
Suh-prised if they did? Again, not really.

Sarcasm/hyperbole do not come across well in a text environment.

I'm probably not very much fun at parties "calm down bruh, I was joking"

You devised a 'workaround' for one of them! 1747-UIC drivers?

Yeah, I've had to do that a couple of times over the years.

 

[GaryS]

I have seen that where the number of characters exceed the display sting length or if the data receiver is the wrong format