I'm a bit confused about STL Load / Transfer Siemens S7...?

[uptown47]

Hi all,

I was under the impression that Load and Transfer operate independantly of the RLO ?

If this is the case the following code shouldn't work, but it does...

A I 0.0
L 20
T MW50
BEC

This code only loads 20 into MW50 if I0.0 is on. However, if the Load was operating independantly of the RLO it would load 20 into MW50 all the time ?

If L and T do look at the RLO before executing, why does the LADder MOVE command of the same code above need to convert to...

A I0.0
JNB _001
L 20
T MW50
_001: NOP 0

Can anyone explain this to me as I'm getting confused about this.

Many thanks

;-)

 

[L D[AR2P#0.0]]

MW50 must be being loaded with something else after the BEC

 

[uptown47]

MW50 must be being loaded with something else after the BEC

The full code is actually:

A I0.0
L 20
BEC
 
(there's a few networks similar to this loading in different values that represent different fault messages. The next block that is called then has this code).
 
T MW 50

I just truncated it together just to try and make my question clearer.

So, is the L.oad instruction influenced by the RLO ?

Many thanks for all your help LD

Cheers

;-)

 

[L D[AR2P#0.0]]

LOAD/TRANSFER are not influenced by the RLO.

The BEC means that when I20.0 is true the block ends and no transfer to MW50 takes place (assuming this is the only place that MW50 is referenced).

 

[uptown47]

That makes perfect sense. Thank god for that... I thought my entire, cobbled-together knowledge of S7 was beginning to unwind....

;-)

 

[JesperMP]

I think this is what you really intended:

      A   I0.0
      JNB _001
      L   20
      T   MW50
      JU  _002
_001: L   0
      T   MW50
_002: NOP 0

In LAD you would have to check for I0.0 twice, with an NO and an NC.

 

[uptown47]

Jesper,

Thank you for your clarification.

On a related note. Is this different in S5? i.e. Are Load and Transfer affected by the RLO in S5 ?

The reason I ask is that I'm just looking at an S5 project that has the following code:

A Q 17.5
L DW 1
T FW 24
 
AN Q 17.5
L DW 3
T FW 24

If S5 operates the same as S7 and my understanding is correct, then regardless of the condition of Q17.5 the two Load/Transfers will be executed.

Is this correct or does S5 operate differently to S7?

(I know this is 2 questions in one thread but it is so closely related I didn't want to start a new thread for it).

Many thanks

John ;-)

 

[KalleOlsen]

If S5 operates the same as S7 and my understanding is correct, then regardless of the condition of Q17.5 the two Load/Transfers will be executed.

Yes they will. In both S5 and S7.

Kalle

 

[uptown47]

If S5 operates the same as S7 and my understanding is correct, then regardless of the condition of Q17.5 the two Load/Transfers will be executed.

Yes they will. In both S5 and S7.

Kalle

Kalle

Thanks for your answer. So is the quoted code just bad programming then? I can't understand why someone would write that code when the Q17.5 bit is meaningless ??

???

 

[PeterW]

Kalle

Thanks for your answer. So is the quoted code just bad programming then? I can't understand why someone would write that code when the Q17.5 bit is meaningless ??

???

Not if he intended to load 20 into MW50 before ending the block.

If it meant to be conditional then obviously it wouldn't work.

 

[uptown47]

Peter,
Thanks for that.

That's what I meant.. the Q17.5 bit is meaningless... I think the programmer has intended to make it conditional but has made a mistake. At least I know now how it is behaving.

Thanks again to everyone for all their help

;-)