On line Ladder Program Editing for RSLogix 500


On
line Ladder Program Editing for RSLogix 500

There
are five basic steps in performing an edit on line. 
1)  Start Edits,
2)  Make Changes,
3)  Accept edits,
4)  Test Edits, and
5) Assemble edits. 
Although
these steps seem very simple there are a few rules to watch out for.

  •  You cannot expand or create a
    data table on line in the SLC, and you must be in program mode (or off line) to
    expand a data table on line in the PLC-5.
  •   You cannot make an on line edit
    if the key switch is in Run Mode.
  •  In the PLC-5, if backplane switch
    8 is on, you cannot make an on line edit. 
  •   You do not need to perform an on
    line edit to directly change a value in the data table such as the preset of a
    timer or counter.
  •   If the processor is in program
    mode, you do not need to test and assemble after accepting.
  •  If the
    processor is in program mode, and a rung is deleted, there is no warning.

Let’s
walk through the 5 step procedure:
Look
at the rung below.  Our objective is to
transfer control of the output to I:001/1. 
If you click on bit 0 and attempt to make a change, nothing happens. 

 Step
1) Start Rung Edits

The
first step is to put the rung into edit mode. 
There are several ways this can be done:
ü 
Double click
the rung number
ü  Right click the rung number and
start rung edits
ü  From ‘Edit’ on the menu bar,
click rung edits, then start rung edits
ü 
Click the
start rung edit icon in the on line editing tool bar just above the ladder view

 

Notice that RSLogix made a copy of the rung for us to work
with.  By looking at the power rails, you
can see the bottom rung is being executed by the processor, and the top rung is
the one you need to make edits to.  You
will also notice the e (edit) and r(replace) in the margin are lower case.  This means the edits are not in the processor
yet.  If you are adding new logic instead
of modifying existing logic, this is the step where you add a new rung.

Step
2) Make Changes

Now
that the rung is in edit mode, changes can be made.  If you were adding a new rung, you can now
add the new logic to the rung.
Be
careful not to add any logic that will fault the processor or cause damage to
personnel or equipment.  In the next
step, the changes we make will be sent to the processor.
In
this example, bit 0 is being changed to bit 1 on the input.  If you are using an SLC, the addressing will
be slightly different.

Step
3) Accept Edits

Now
that your rung is set up as you need it, it’s time to send the edits to the processor.
There
are several ways to perform the next three steps.
ü 
Right click
the rung number, and accept edits
ü  Click Edit | Rung Edits | Accept
rung from the menu bar
ü 
Click the
Accept Edits icon in the on line editing tool bar as shown below

If you need to accept multiple rung edits, you can hold down the
CTRL key and click on the rungs you need to accept, or if you have many edits
all together, you can click the first rung number, hold shift, then click the
last rung number of the range you wish to accept. Notice in the margin rung 1
is marked for insertion, and rung 2 is marked for removal. The I’s and R’s are
capitol because the edits are now in the processor.  Look at the power rails.  You can see the old rung is still being
executed by the processor.

Step
4) Test Edits

When you test edits, the new or modified rungs will become
active.  The old rungs will be left in
the processor until we are sure our new rungs are working properly.  Be aware that if you change an output
address, there might no longer be logic writing to that address.  This means that you could abandon a bit in
the ON state.  If you are modifying an
input type address you should also be careful. 
If the rung was previously true, you may want to make sure your new
logic is also going to be true at the moment you accept, or the the output may
shut off.
Let’s test the edits, and you will notice the new rung(s) are
active.  If the edits do not work the way
you anticipated, you can untest to revert to the old rung while you make other
changes to the new rung.

Notice
the power rails:

Step
5) Assemble Edits

If you logic is working properly, go ahead and assemble the
edits.  Assembling removes the old rung,
and the edit zone markers.  After
Assembling, you may want to save your work to the hard drive.

Notice
the Logic now appears to be normal:

Leave a Reply