S7-300 Program

powder

Member
Join Date
Sep 2005
Location
Cincinnati
Posts
2
First, I appologlize in advance for my ignorance but Siemens PLC's are not what I am most familiar with.

WE have a treatment system we purchase from a OEM from Italy. We would like to make some small changes and encountered some problems. All of the blocks are displayed in STL. I know in the past on other Step 7 processor's I could swtich from STL to LAD to FBD with no problem. They were S7-400's though?

When I attempt open a block and/or attempt to switch from STL to LAD with the S7-300, I get these messages.

First:"There are no Parameter and local variable names available because their description is not available or cannot be assigned"

Click OK and

Second:"The open block does not contain any symbol information"

Click ok and the block opens in STL.

Any help or suggestions with this is appreciated in advance.

Regards
 
Before attempting any modifications, get hold of the Step 7 project archive supplied by the OEM. (Usually a zip file))
 
JesparMP and L D[AR2,P#0.0],

Thank you for your Replys and as you stated I was using a backup. I am now using the origianl I no longer get the 2 messages and I have a program with comments and descriptions(although in Italian). But I still have a problem going from STL to LAD, only some of the networks convert. Any other thoughts?

Regards
 
Not all STL will convert to ladder.
There's a couple of ways to break the STL code in sections (without affecting its functionality) in order to display it in ladder.
Some other more complex STL networks you simply cannot display in ladder.
Do a search on here and you'll find more than a couple of ways of working out the STL to Ladder conversion.
 
Stl/lad/fbd

exactly , akotta ras is right.
STL is the easiest way of writting the program.But when you need it convert to other form like LAD or FBD then certain modifications are required.
just for example.
you can write a program for a timer in this way :
A I 1.0
L S5T#5S
SF T10
A T10
= Q 4.0
THIS PROGRAM WILL RUNN PERFECTLY.
But it can not be changed to LAD or FBD.
you will have to write it as
A I1.0
L S5T#5S
SF T10
NOP 0
NOP 0
NOP 0
A T10
= Q4.0
NOW YOU CAN CHANGE IT.
I THINK THIS WILL HELP YOU.
 
panthripu said:
STL is the easiest way of writting the program.
I'm sorry but I disagree. LAD is the easiest way to write a program and to troubleshoot it. STL is the most effective way to program, but by far not the easiest, and certainly not the easiest to troubleshoot.

Kind regards,
 
Stl/lad

yes friend, you are right , for trouble shooting both LAD and FBD are very friendly.But for writing and modifying program , i prefer STL.
 
Because there are three terminals/ports you're not using. In LAD or FBD all terminals of the symbol have to be programmed. By placing a NOP 0 in the place of the terminal, you state: I know the terminal is there, but I don't use it". If you don't place the NOPs, you basicly say the terminals are not there, so the program can't be converted to LAD or FBD.

Kind regards,
 
jvdcande said:
Because there are three terminals/ports you're not using. In LAD or FBD all terminals of the symbol have to be programmed.

Wow that went way above my head !!
"Terminals of the symbol". Given a Up Counter can we count how many terminals will this symbol have?
 
If you place the Up Counter symbol in your LAD or FBD program or if you it look up in the LAD or FBD manuals, yes you can.
UpCounter.gif

As you can see it has 4 terminals on the left side and three on the rigt side. You have to program these from up to down and from left to right, so the sequence is
  1. CU
  2. S
  3. PV
  4. R
  5. Q
  6. CV
  7. CV_BCD
The first terminal (here CU) has to be programmed always, the others might be omitted by placing a NOP 0 in their place when programming in STL or by being left blank if programming in LAD or FBD. If you know these rules, it's almost child's play.

Kind regards,
 

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