Is there any hidden instructions outside the ladder logic?

[shaydzmi]

Hi,
I'm an absolute beginner in PLCs..

I have an Allen Bradley SLC5/03 PLC installed on a machine, the program is working well, I uploaded it to my PC, in order to learn how it works, but I came across a weird things, one of them:
There is an input (I:3/4) that doesn't appear in the ladder program, but still does its work, it counts a distance. how could this happen?
The program I got from the PLC (format: .RSS) is identical to the one I got from the machine manufacturer (in PDF format).
Is there any hidden instructions in other places?
The PLC is connected to an HMI, but the mentioned input counts even when I disconnect the HMI.

any ideas?
I can upload the program in RSS and PDF if it's necessary.

Update1:

The project files:
PDF
RSS
I/O Configuration:

The Input 3/4:

 

[parky]

It sounds like there is a high speed counter but your definition about counting is not clear, there could be a counter card (HSCE).
Some years since I did SLC so cannot remember how it is configured perhaps give us some indication of the cards mounted on the rack & their part numbers
also a copy in PDF of the logic would be helpful.

 

[shaydzmi]

Thank you, I've updated my post.

 

[parky]

perhaps upload the code in PDF format, you have only shown the rack/cards & drawings of the Inputs 3/0-3/4 it is evident that there is no HSCE card so there could be a number of possibilities i.e. indirect addressing or the I/O is moved to an integer file.

 

[geniusintraining]

perhaps upload the code in PDF format,...

They are in the first post

 

[geniusintraining]

shaydzmi,

Change the RSS file to a ZIP and upload it again, then someone will take a look, the PDF is to large to search

 

[parky]

Yes I missed the files, have searched it & cannot find I:3/4 what counter is counting for that distance? are you sure it is not one of the other inputs? seen this before where either I/O is not per drawing (comments) or for some reason the input was changed & either the sensor was moved & drawings were not updated or the original programmer did a last minute change & not updated something.
There are 17 instructions where I:3/xx are shown none of these are I:3/4, the counters use I:3/3 as a direct contact to counters

 

[parky]

A bit more information:
is the input I:3/4 input LED flashing if so then it does not mean it is being used in the program.
Is there a value changing on the HMI which you assume is driven from the input, if so I suggest you look at the HMI program, find the variable that is changing, search for that variable in the PLC code & see what is changing it.
Again it could be that the count you see on the screen called "position count" although seems to point to a sensor "Position Sensor" (or what ever they are called) it maybe this is not the case.
I do suggest if you can work backwards from the count from HMI or code, if you cannot find it then it is probably not used.

 

[JesperMP]

It could be that there is a Discrete Input Interrupt programmed for the input.
Look at the DII tab of the S2 status file.
Counting would be a probable application for a hardware interrupt.

I think that the file address specified by S:46 does not appear in the cross reference as being written to (I might be wrong, it has been 15+ years since I worked with SLC500), so that makes it difficult to establish the connection between the input and the count address.

 

[shaydzmi]

shaydzmi,

Change the RSS file to a ZIP and upload it again, then someone will take a look, the PDF is to large to search

Done here, I couldn't edit my original post.

what counter is counting for that distance?

It measures how wide is an expander, it goes between 280mm and 1650mm.

are you sure it is not one of the other inputs?

Yes.

seen this before where either I/O is not per drawing (comments) or for some reason the input was changed & either the sensor was moved & drawings were not updated or the original programmer did a last minute change & not updated something.

It happens, but not in my case!

the counters use I:3/3 as a direct contact to counters

This is another meter counter.

A bit more information:
is the input I:3/4 input LED flashing if so then it does not mean it is being used in the program.

It flashes only when I push the push button related to it, and changes the value on the display, when I remove the the input I:3/4 from the card no changes happen.

Is there a value changing on the HMI which you assume is driven from the input, if so I suggest you look at the HMI program, find the variable that is changing,

Yes, but I don't have the HMI program, but I guess I know where are the variables, they are on the (LAD21).

 

[JesperMP]

Post a screenshot of this tab from the status file:

Also do a search for S:2/12, S:33/10, S:50 and S:52.

 

[shaydzmi]

S:2/12 found only on file 2 rung 0 (OTL).
---------------------------
S:33/10 was not found.
---------------------------
S:50 was not found.
---------------------------
S:52 was not found.
---------------------------

 

[arpus4KM]

Done here, I couldn't edit my original post.


It measures how wide is an expander, it goes between 280mm and 1650mm.


Yes.


It happens, but not in my case!


This is another meter counter.


It flashes only when I push the push button related to it, and changes the value on the display, when I remove the the input I:3/4 from the card no changes happen.


Yes, but I don't have the HMI program, but I guess I know where are the variables, they are on the (LAD21).

I think he was asking which of the C5 Files is the counter you are saying is being incremented by the I:3/4?

 

[geniusintraining]

Done here, I couldn't edit my original post..

Its not the same as the PDF, do you have the same one in the PDF?

Odds are someone just changed the program and 3/4 was not needed

 

[JesperMP]

S:2/12 set high means the interrupt is enabled.
S:47 (Slot) = 3 and S:48 (bit mask) = 10h means that DII is looking at input I:3/4.
S:46 = 7 means that program file 7 is called when I:3/4 goes high.

edit:
in the PDF, in program file 7, N7:158 is counted up or down based on some other conditions.
I think this explains it.