sequential program implementing

Hi Experts,


I would like to ask about sequential programming in PLC and particulary in Step7, i know there is internal coils interlock methods in side and wich is for very simple programs, but there is also thd S7-Graph in the other side wich is non recommended from many plc programmers.

Actually i can use the two methods, but what if the program was long ? I've heared that there is also the jump distributor wich is based on a byte wich contains a number for specific step, and there is another method based on integer for step indicating with use of MOVE instruction to step forward the sequence.


Could any body put a simple program with only 3 steps to introduce me to the two last methods described above? I appreciate any comments or help to this thread.

Thanks in advance!

I would use a shift register normally.

Kindly can you pls post a wrotten code to do a simple task in 3 steps and it would be generous if its for step7

This video shows one method of writing a sequential program in ladder:

https://www.youtube.com/watch?v=rCa_U6YATTA

Thanks !

Hi

Hi,


Check this post:
http://www.plctalk.net/qanda/showthread.php?t=45009

Kind regards,
G

in STL like I do it like this

In STL I do it like this:

L #STEPNR
L 1
==I
JCN NO1

// ACTIONS
SET
= Q0.0

// TRANSITION
A I0.0
JCN NO1
L 2
T #STEPNR

NO1: NOP0


But instead of an integer #STEPNR, you can also make an array of bits...

Like this:

A STEP.index[1]
JCN NO1

// ACTIONS
SET
= Q0.0

// TRANSITION
A I0.0
R STEP.index[1]
S STEP.index[2]

NO1: NOP0

I don't think there's a real good reason to use any vendor specific sequencing instructions or methods. A simple move with the desired step number into an integer memory location usually works quite well and is easy to follow. Of course everyone has their own favorite methods.

If you have Step7 graph- why not use it? It's very easy
Go through the quick start guide installed with graph. Don't be scared

adisharr said:

I don't think there's a real good reason to use any vendor specific sequencing instructions or methods. A simple move with the desired step number into an integer memory location usually works quite well and is easy to follow. Of course everyone has their own favorite methods.

Click to expand...

I'm also a fan of the integer step method.

I would avoid something like a jump distribute. I try to avoid jumps when I can. I'd usually rather see the code execute as false than wonder why it is greyed out (because I jumped over it).

JRW said:

If you have Step7 graph- why not use it? It's very easy
Go through the quick start guide installed with graph. Don't be scared

Click to expand...

I second this
Fault finding is a breeze when using graphcet (SFC). And it creates logical structure in a sequential program