Update status word in step7??

[Robert Carlsson]

Hey all!

I am developing a block, and this block includes several error checks. If the return value equals 0, all is good. Therefore I use this code:

L #iReturn
JN err

where iReturn is the return code checked and err is the label where the error handling is conducted. It seems though, that the status word is not updated, and therefore the JN instruction isn't executed as expected. I've added a small example, where I excanged #iReturn for W#16#5 for debug reasons.
Do I need to manually update the status word? AFAIK this should be updated automatically?

 

[manmeetvirdi]

Hi there
Why dont you go as below:

L #iReturn
L w#16#0
<> i
JC err

 

[Robert Carlsson]

Yeah, the error checking code looks like this right now:

L #iReturn
L 0
==I
JNB err

Just thought it would be more effecitive to just load the iReturn and jump if it differs from zero.

 

[L D[AR2P#0.0]]

A look in the siemens help for the load instruction reveals all:

 

[Robert Carlsson]

You are correct. I'm sorry, my real qestion was if it's possible to update the status word, or do I have to do the comparison as it's done right now?

 

[L D[AR2P#0.0]]

To answer your specific question, yes you can update the status word:

 

[Robert Carlsson]

Hehe, but this was not quite what I wanted, since I want the value of ACCU-1 evaluated, and the result put in the status word, rather than manipulating the status word, then I could just skip the comparasion and just assume all went well or failed?