S7 problem with setting bit in word using pointer

svdhorst · Mar 2, 2009

Hi,

I know there already are a lot of threads about using pointer, but I can't find
the solution to my problem in any of them.

I'm trying to set a bit in a word using a pointer. The word is variable, so I made a pointer. The bit I want to set has an offset to the first bit in that word of 1.0. I tried this code:

L P##VARIABLE_WORD
LAR1
L W [AR1,P#0.0]
T #DBNR
OPN DB [#DBNR]
A #CONDITION
S DBX [AR1,P#1.0]

This doesn't work. I tried some other things, but nothing seems to work.
Please help!

Thim · Mar 2, 2009

svdhorst said:
Hi,

I know there already are a lot of threads about using pointer, but I can't find
the solution to my problem in any of them.

I'm trying to set a bit in a word using a pointer. The word is variable, so I made a pointer. The bit I want to set has an offset to the first bit in that word of 1.0. I tried this code:

L P##VARIABLE_WORD
LAR1
L W [AR1,P#0.0]
T #DBNR
OPN DB [#DBNR]
A #CONDITION
S DBX [AR1,P#1.0]

This doesn't work. I tried some other things, but nothing seems to work.
Please help!

What declaration is variable_Word?? And what is stored in there??

svdhorst · Mar 2, 2009

Thim said:
What declaration is variable_Word?? And what is stored in there??
I assume that you have the adress for the possition in there.
If So try this declare it as Dword (temp) and write
L variable_word (Dword)

VARIABLE_WORD is of data type POINTER.
Maybe it's not really clear what I want:
At the block call I enter a fixed word (i.e.: DB228.DBW2).
I want to set the first bit of the second byte in that word, so that would
be DB228.DBX3.0 for this example.
The thing is that I need to do this more words, so therefore I want to use a pointer.

Thim · Mar 2, 2009

svdhorst said:
VARIABLE_WORD is of data type POINTER.
Maybe it's not really clear what I want:
At the block call I enter a fixed word (i.e.: DB228.DBW2).
I want to set the first bit of the second byte in that word, so that would
be DB228.DBX3.0 for this example.
The thing is that I need to do this more words, so therefore I want to use a pointer.

check this and let me know

L D[AR2P#0.0] · Mar 2, 2009

Is the code required for an FC or FB ? (Thim's example is for a non-multiple instance FB)

Thim · Mar 2, 2009

Oh sorry if i did something wrong.
Can you please explain me what LD? So i know for next time!
I tested it and seemed to work but didn't test it for multi instance

svdhorst · Mar 2, 2009

L D[AR2 said:
Is the code required for an FC or FB ? (Thim's example is for a non-multiple instance FB)

I'd prefer an FC.

@Thim: trying your solution now, I'll let you know if it does the trick. Btw, thanks for the help so far!

Edit:
Thim: Your solution works like a charm

Thanks very mutch!
I see you used an any-pointer. Is the problem I had that I used a normal pointer?

PeterW · Mar 2, 2009

svdhorst said:
Hi,

I know there already are a lot of threads about using pointer, but I can't find
the solution to my problem in any of them.

I'm trying to set a bit in a word using a pointer. The word is variable, so I made a pointer. The bit I want to set has an offset to the first bit in that word of 1.0. I tried this code:

L P##VARIABLE_WORD
LAR1
L W [AR1,P#0.0]
T #DBNR
OPN DB [#DBNR]
A #CONDITION
S DBX [AR1,P#1.0]

This doesn't work. I tried some other things, but nothing seems to work.
Please help!

My rusty take on what you are doing here..

L P##VARIABLE_WORD
LAR1

you are loading the pointer AR1 to point to the absolute location of #VARIABLE_WORD

L W [AR1,P#0.0]
T #DBNR
OPN DB [#DBNR]

You transfer the value held in #VARIABLE_WORD into #DBNR and open the Data Block with that value. So #VARIABLE_WORD is a data block ID.

A #CONDITION
S DBX [AR1,P#1.0]

On a condition you set bit 0 in a word in the data block that is the same as the DB no..

ie if #VARIABLE_WORD was equal to to 5, you would have set set DB5.DBX6.0 to one ?? which is bit 0 of DBW5.

As I said I am rusty ☯

Thim · Mar 2, 2009

svdhorst said:
I'd prefer an FC.

@Thim: trying your solution now, I'll let you know if it does the trick. Btw, thanks for the help so far!

Edit:
Thim: Your solution works like a charm Thanks very mutch!
I see you used an any-pointer. Is the problem I had that I used a normal pointer?

Never used a pointer before but i think it has to do with the structure of it Any pointer has area of 8words.
Like you see i strip down the anypointer by moving the DB number in "DBNR" then i move the possition in "Bit".
Don't see you doing this in your code i think you can strip down the pointer as well, but then you will probably also need to point first to the DB-area and Bit-area.
Sorry for the bad english

Thim · Mar 2, 2009

Extra:
If you want to use Pointer then i think you need to change
Not sure of it, but someone will correct me if so

LAR1 P##variable_Word
L W [AR1,P#4.0] // change in to [AR1,P#0.0]
T #DBNR
L D [AR1,P#6.0] // Change into [AR1,P#2.0]
T #Bit

OPN DB [#DBNR]
L #Bit
LAR1
A #condition
S [AR1,P#1.0]

svdhorst · Mar 2, 2009

Thim said:
Extra:
If you want to use Pointer then i think you need to change
Not sure of it, but someone will correct me if so

Yeah I figured this out myself after reading your previous comment.
I know what I did wrong now. I tried to set a bit in the place of the pointer where the DB number is stored in stead of the address.

Thanks for everything!!

L D[AR2P#0.0] · Mar 2, 2009

Thim said:
I tested it and seemed to work but didn't test it for multi instance

..try it with a multiple instamce example and see what happens

S7 problem with setting bit in word using pointer

svdhorst

Member

Thim

Member

svdhorst

Member

Thim

Member

L D[AR2P#0.0]

Lifetime Supporting Member

Thim

Member

svdhorst

Member

PeterW

Member

Thim

Member

Thim

Member

svdhorst

Member

L D[AR2P#0.0]

Lifetime Supporting Member

Similar Topics