Using pointers in GX IEC Developer

Hi all,

The thing I'm trying to achieve is actually quite difficult to explain, but since there's no use posting this topic if I can't explain, I'll give it a go anyway...

I have created a DUT ("DUTDigitalInput") consisting of 4 BOOL's. The DUT represents one digital input, with extra information that can be used to "overrule" the input via software, for instance during commissioning.
In the GVL I have defined a number of digital inputs, each of the type DUTDigitalInput.

Now I would like to create an FB where I can address each variable defined in the GVL one-by-one to check whether it has to be overruled or not. Of course I would prefer not to call them by name or even address. Instead I would like to input the startaddress and number of inputs in the FB, and internally in the FB I can then address the correct variable.

My guess is I have to use pointers for this, but I do not really know how to create and use these in GX IEC Developer. Any help would be much appreciated.

My apologies if it isn't exactly my explanation isn't exactly clear. I have tried to explain as good as possible.

Thanks in advance,
Caspar

Hi cmulder,

Perhaps you may want to consider those two additional access levels :
- When handling one element : initialize your FB by copying your DUT var in some one-dimensional array
- When handling multiple elements and indexing both var and data units in the var : why not immediately build some two-dimensional array used as a common recipient for all your values ?

Regards
Laurent

There aren't pointers in the IEC specification

It may be hard to use pointers if they aren't supported.

Perhaps you should consider declaring your bits as an array of bits and then use an index variable to index into the array of bits.

Peter,
you're right, as I've found after carefully reading the manual (RTFM, right!!!). In the user manual of the QnA-series pointers are mentioned. However, the pointers discussed there are not pointers as used in for instance C++. My mistake...

Laurent,
I understand the first option you supplied. However with my limited knowledge of the English language I can't really understand the second option.

The reason I'm using DUT's is because my dear colleagues have set up a company standard with Siemens Step7, thus using UDT's and DB's. Now I'm trying to "copy" this standard to Mitsubishi. Of course I'm aware that I can't copy everything, but I want to try to keep to this standard as much as possible.

Regards,
Caspar