Tech and application note for pointer in S7?

Hello

is´t anyone who has any good tutorails or tech and application nots for pointer in S7??

google for Hans Berger's book on STL/SCL and buy a copy - this is a good reference for S7 pointers.

Here is a recent thread showing a simple example using pointers: - http://www.plctalk.net/qanda/showthread.php?t=31958

and here is a more advanced example:-

http://www.plctalk.net/qanda/showpost.php?p=143085&postcount=4

Thanks agin L D[AR2,P#0.0] for you answer, but i still don´t get it. i have look in to yours using pointers: - http://www.plctalk.net/qanda/showthread.php?t=31958
can you describe for me what you are doing in the code??

Yes, but it will take me some time to create a detailed reponse. You need to do some backgound reading concerning area pointers and what they contain. Various pictures of the bit pattern in an area pointer have been posted, I just can't find one at the moment. Have you run the posted code and looked at the registers when monitoring the block - this will also help.

Hi Berra,

What is it that you want to achive with the pointer? Is it just curiosity or some special application? Knowing this makes it easier to give you a more specifik answer.

/Wille

Please see below a small snippet of code which uses I1.0 directly addressed, and then the same access using a run time created indirect access to I1.0

I have deliberately loaded the pointer area into the accumulator first, and then transferred it to address register 1 (AR1) so you can see the values being loaded as hex codes (I would normally load the values directly into AR1). As you can see, once a valid area is loaded into AR1, the display conveniently shows you the area being used. I have also shown the area pointer (now you can see where the byte address is stored in the pointer, this explains why you need to shift a byte address left 3 bits to convert it to an area pointer)



The area coding ZZZ, is as follows:
000=Peripheral(PIW/PQW)
001=Input(I)
010=Output(Q)
011=M
100=DBX (global DB)
101=DIB (instance DB)
110=L (temp local data)
111=V (temp local data of the preceding block)

Here is another snippet of code showing the loading of different areas first into the accumulator and then AR1


Finally, here is FC277 shown with extra comments and the online view with the byte address set to 1 and the bit address set to 0, the block is thus accessing I1.0 using indirect addressing. (I have chosen to limit the max byte address to 255 for my 317 plc)


Chew this over and come back with any questions.

Tanks L D[AR2,P#0.0] i will be trying to understand the codes under the weekend then i can get back to you with some question if it´s ok?