Step 7 SCL DB Addressing

[AlecTek]

Hello,

what is wrong with the program like below to write 100 to DB81.DW24?
%DB81.DW(IDX :=24) := 100;

Or how should I write the program?

Thanks!

db81 is not an array, it is a structure of different type of data, I would like to access the word at the offset 24 of db.

[L D[AR2,P#0.0]]

plc - s7-300 or s7-1500/1200?

[AlecTek]

S7-1500, TIA POrtal 15.1


Thanks

[L D[AR2,P#0.0]]

Here's my preference over using poke:

[L D[AR2,P#0.0]]

A better solution might be to read the structure element, modify it to what you want and then write it back - any reason why not to do that?

[AlecTek]

You saved my day!

I am doing some supplements to an existing system, so your poke is the best solution to me.

Thanks a lot!

[L D[AR2,P#0.0]]

? I'm not doing a poke.

[mk42]

1500's & SCL generally work with the tags of a structure, instead of the addresses that the structure resides in. The "should" is to restructure the code so you can do it with tags.



If you can't (and there are very few reasons that I've seen that don't boil down to "I don't want to do things the new way"), you can only use absolute address if you make it a non-optimized OB. Peek/Poke instructions are the best way to make it a variable offset to a DB.

[AlecTek]

Sorry L D, when you said your preference over poke, I just read as poke. I don't really know poke, but your way is pretty simply to me.

mk42, I am trying not to touch any existing stuff unless have to, I don't want to go to site and troubleshooting a whole day for a minor change.

BTW, I don't understand why siemens not making simple things simple. 10 years ago I was spending a day to find the way to set bits in a word, and after 10 years I spend another day to recall the way i did it. Anyway, thanks for all the help!!

[mk42]

Originally Posted by AlecTek

mk42, I am trying not to touch any existing stuff unless have to, I don't want to go to site and troubleshooting a whole day for a minor change.

Fair enough, I guess. Legacy stuff is what legacy stuff does.

Originally Posted by AlecTek

BTW, I don't understand why siemens not making simple things simple. 10 years ago I was spending a day to find the way to set bits in a word, and after 10 years I spend another day to recall the way i did it. Anyway, thanks for all the help!!

For what it's worth, the new stuff does have an easy way to do it, if you're saying what I think you are. To change a bit in a word in 1200/1500, use slice based addressing: #TagName.%X0 for bit 0 as an example.



https://support.industry.siemens.com.../view/57374718

[AlecTek]

How do we extract bits of word in WinCC Advanced if not using scripts? (TIA Portal 15.1)

[mk42]

Originally Posted by AlecTek

How do we extract bits of word in WinCC Advanced if not using scripts? (TIA Portal 15.1)

Most of the animations let you animate based on a single bit in a tag. There are system functions to read/write a single bit in a tag. Alarms can only be set up that way.


What were you trying to do?

[AlecTek]

Thanks mk,

I got a status word, each bit means something, and I would display some status for example Moving = b1. I made a faceplate properties\status will interface the status word.

I tried something like status.%X1 but not work.

So then I try the VBscripts (this is WinCC advanced). I made a faceplate tag b1:bool. and I tied the followings:

SmartTags("b1") = ((SmartTags("Properties\status") And 2) = 2)
b1 = SmartTags("Properties\status") And 2
b1 = ((SmartTags("Properties\status") & 2) = 2)
If SmartTags("Properties\status") And 2 Then
b1 = True
Else
b1 = False
End If

and none of above work neither. Really weird, because I did similar faceplate long ago using wincc flexible.

[drbitboy]

http://chris.wastedhalo.com/2010/10/...binary-in-asp/


?

[AlecTek]

OMG

b2 = CBool(SmartTags("Properties\status") And 2)

Thanks drbitboy!