Allen Bradley / RSLogix Dynamic Arrays

Going back to rocket's original question....

No, you cannot re-size array tags dynamically with code.

You cannot even re-size array tags online.

The problem here is that array tags allocate their data into contiguous memory space. This allows them (amongst other things), to be the sources and targets for communications with other PLCs, and useful where you want to "index", or indirectly address, elements within the array.

I cannot see the point in wanting an array to be smaller on the days when there are few data to collect, and larger on the days when there are a large number of data to collect. You will certainly need the memory space for the large array, so allocate it anyway, to hold the maximum data you envisage.

Nothing else in your application will need dynamic memory allocation, so trying to recover "unused" array space doesn't give you anything.

One useful thing about not being able to change the size of array tags, is that the programming software can "estimate" memory usage when downloaded to the target processor.
 

Similar Topics

Hello all. I have been working with an SLC 5/04 system, which houses various Digital and Analog INs and OUTs, up to Slot 29. I am currently...
Replies
3
Views
2,477
1.the black switch is master start/stop switch 2. When red pushbutton is pressed once, both motor 1 and 2 should run continuously 3.if you close...
Replies
3
Views
1,739
how can i use my allen Bradley RSlogix PLC to gate triggering to a TRIAC or thyristor actually i want to gate triggering to the TRIAC or...
Replies
12
Views
6,232
Hello All, I am fairly new to PLC programming and really only know how to use the basic functions of RSlogix 5000. I have a new project I will...
Replies
14
Views
24,127
Hi All, I wonder if anyone knows the answer, or even if its a stupid question, as to whether the ALMA / ALMD blocks that rslogix uses for alarms...
Replies
5
Views
6,242
Back
Top Bottom