Index Registers in Function Blocks

[flylikechris]

Hi guys, I have run into a problem where I am trying to use a device offset in a repeat call function block. My understanding is that I only have a certain amount of these Z/V registers (16 total). Do you guys know of another way I can call a device, with a variable offset? example, load a value of "1002" into Z0, and then call D0Z0, but really be looking at D1002. I am passing a function block a configurable I/O start location (constant). I then load this start I/O location into Z0, and call D0Z0 in my function block. Any help is greatly appreciated. Thanks!!

[JRoss]

Not really, that's the way to do it. You need more than 16?

[flylikechris]

Thanks for the reply. The more I think about it, the more I realize that this will work just as I need it. I guess I will just have to be careful about how I manage these registers among different block types.

[Gambit]

If you are using IEC Developer or GX Works (structured). You can also use an Array. For instance Arrayname[0] or ArrayName[index] where index is a word device Edited October 21, 2013 by Gambit

[jorgensen]

When using index registers in a block it is good practice to save/restore the value to a local variable or use push/pop, and if the index value should be retained restore and save it to a global variable. You may also check the U/G addressing mode for module reference in a block. Edited October 21, 2013 by jorgensen

[flylikechris]

I know this is an old thread, but I wanted to say thanks to jorgensen for his input. Right now I am opening a block call, and immediately writing the index register value to a temporary location. Then before exiting the block, I write the initial value back to the index register. This lets me use the index registers freely throughout the block. Thanks!!