scan time slc

[Hojland]

I have a slc 552 which uses up to 220 ms in scan time. Memory used 7990 and 2070 memory free. There is some indirect programming in the code. Will it help to install a 553. Dos it work faster or is it only the memory that is diffrent

 

[JesperMP]

Hej Hojland.

It is only the memory that increases.

SLC500 is not super performant by todays standards, but still .. 220 ms scan time is extreme. Something must be wrong.
Indirect addressing do take significantly longer than direct addressing, but that cannot be the only explanation. I am guessing that there is some recursive code that is the main culprit.
Is this a newly developed program ?

 

[Hojland]

Hey Jesper

I have tryed to stop the indirect adressing, by not calling the Rutine contaning the indirect adressing. When doing that it only takes 20 ms in scan time. So it is the indirect adressing. Thanks anyway

 

[Bob O]

Look for LBL and JMP instructions in that routine. This may be what JesperMP was talking about.

 

[JesperMP]

Try to contact the original programmer (if it isn't yourself).
And then investigate what is the code with indirect addressing is supposed to achieve.
Post your findings here.

 

[JaxGTO]

A lot of times a programmer will get lazy and use indirect when they really didn't need to. You may also be able to break it down into alternate scans (lower x on one scan and upper y on the next scan).
Biggest question is: Is the slow scan effecting the process or do you just want to find out why its that slow?

 

[Hojland]

The machine is running ok. But we have trouble with the HMI. (Panelview Plus) When you press the buttons in rapid succession, the HMI comes with errors. N99: 12 - N99: 14 Is the time, that the panelview is writing til PLC. See Attached Image

 

[JesperMP]

This could have to do with the communication is slow, which can be caused by the long scan time.

You are not really answering the questions, so that makes it difficult to help you.
Is this a new program, an old program, or an old program that has been modified ?
Are you the original programmer ?
What is the code with indirect addressing supposed to achieve ?

 

[JaxGTO]

You can also put in a few SVC instructions in the SLC program. This forces the SLC to service communications ports.

I have one SLC 553 with a very large program. I placed a SVC port 1 about every 100 rungs and it really helped the HMI updates. You can also set your HMI screen update to 1 second. Most data does not need to be updated any faster then that.

Also have the HMI read only 1 or two files so it can read faster using block reads.

 

[Operaghost]

The window you are showing is not actually showing errors. Those are information messages stating that the values 44, 11, and 13 were written to three specific tags/addresses.

I don't have a PV here but I think you can suppress those if you can get into the setup. I might be mistaken though.

To fix it, you would need the FactoryTalk View ME application and the FactoryTalk View Studio software. In there you can tell it to not display information type messages. They are a nuisance when configured to pop up like that. I usually only show errors and turn off warnings and information messages. The default setting is that information messages are turned off. Someone turned them on.

OG