S7 Code Network Not updating

[Neil stokes]

Afternoon Gents,
I have a small problem whereby the Network I am monitoring is not showing an update on the output coil.Instead of being green it is black
There are 2 inputs in series that engergise the output one is green the other is balck even though they are on at the i/o card.
If i look at the status in a Vat table I see the output on and the corresponding Inputs also at 1.
This network is the only one i have an issue with all others in the FC are ok
I assume a software glitch but I am sure someone has seen this before



Appreciate you help

Regards Neil Stokes

 

[Zane_Terblanche]

Do a xref and check that the output isnt being used elswhere in your program. (I have done it many times before) 9 times out of 10 you will find it is being over written somewhere else.

 

[Neil stokes]

Hi Zane and thanx for the reply.
Xref reveals only one plce that the output is being written to.
STrangley enough its the inputs that do not show active status.
For example
In FC1 I1.6 is being processed and shows active state 1 (green when Monitoring)
The same input in FC2 shows Black when Monitoring.
This is the network code
My issue is
RLO on 1.5 is 1
RLO on 1.6 is empty ( not Zero)
RLO Q21.7 is empty (Not Zero)

A Q 15.6
A M 101.5
O
A I 1.5
A I 1.6
O I 9.4
= Q 21.7

If i switch to ladder then the NO contact just shows black and output coil is black which is oviously not true

Hope this gives you more information.

Effectively the realworld I/O status is correct but the graphical representation is not.

I have tried an old back up and two seperate PG units--same issues

 

[Zane_Terblanche]

Ok, what happens if you force the status of I1.6? Does the RLO change?
Have you tried running it through PLCSim?

 

[Neil stokes]

I Zane, It works perfectly through the simulator?..Go figure!
Also V5.4 and V5.5 show the same issue

there is no advantage of forcing the I/O channel as in Fc1 the input is high anyway.

 

[Zane_Terblanche]

That is a real head scratcher. Ill have a think about it today.

 

[L D[AR2P#0.0]]

Use a temp variable for Q21.7 and then have a separate network controlling Q21.7 and then monitor the simpler network. I have also seen this where certain networks or even parts of networks do not update in ladder view.

Can you post the project (copy the blocks to a library and post the archived library)