Siemens STL question

[RickardEM]

I'm having trouble trying to convert this code to ladder, anyone able to help me?

A M4.0
A M4.1
A M117.0
AN M17.7
A (
A I38.6
AN I3.7
O (
A M4.5
FP M231.6
)
)
JNB M001
= M100.0
M001: NOP 0

\Rickard

 

[Lare]

FB is edge positive. NOP 0 is no operation.


If you delete FP and JNB command then step7 classic editor can convert it to ladder view without trigger.

 

[drbitboy]

Can this

...

JNB M001
= M100.0
M001: NOP 0

be replaced by this

...
S M100.0

?

 

[parky]

I'm a little rusty, & hope I have the brackets shown right then the attached is what I think it is in ladder
The JNB is jump if RLO is 0 in other words jump if not true
as the RLO will be true on the rising pulse M100.0 will become true, however, as this is a pulse the next scan it will be false but as the JNB will jump over the M100.0 it will still be true.
So in effect it does appear that M100.0 once set will be true until something else resets it. I would check all instances of M100.0 as it could be reset elsewhere
So in reality putting M100.0 in place of the pulse function would not work perhaps "IF" M100.0 is reset elsewhere then you would use that pulse to SET M100.0
Note: as this is not Siemens I had to use a jump with a not M231.6

 

[parky]

Here is a simple link to S7 STL
http://www.plcdev.com/files/plcdev/STL-cheat-sheet-by-alphabet.pdf

 

[drbitboy]

Not that I have ever done this before, but as far as I can tell, the following STL and LAD logic execute identically from TIA and a PLCSIM S7-300.

Note that, in the STL,

• the line 9 A B14_5 RLO is 1, and
• the line 10 FP Edge_Memory_stl memory bit %M231.6 is 1

even though all of the RLOs up to that point are 0.

​

 

[L D[AR2P#0.0]]

You can use the pos block as an alternative:

 

[drbitboy]

Ooh, nice catch; in TIA it's the -|P|- instruction.

​

Interesting that the input RLO to the -|P|- does not affect the one-shot calculation based on the operand; that could be quite the gotcha if it was not known that it worked that way. I am pretty sure that means this will also work:

​

although it is not as clean.

 

[RickardEM]

Thank you for all your answers. It makes a lot more sense now.
I was modifying the code a bit, didn't think it would matter but I realize now that it will. Sorry.

The code calls an FC instead of setting a coil.
A M4.0
A M4.1
A M117.0
AN M17.7
A (
A I38.6
AN I3.7
O (
A M4.5
FP M231.6
)
)
JNB M001
CALL FC30
POS:=111
DEST:=112
ID:=1
ID_TYPE:=1
SYSTEM:=100
M001: NOP 0

\Rickard