Immediate input with Compact Logix

[(8{)} ( .)]

Hi All,

I thought that this would be simple. I converted an SLC program which used IIM instructions (Immediate input) to Compact Logix. The problem is I can't figure out how the Control logix does immediate input data. Perhaps using interrupts? Any ideas?

Thanks,

(8{)} .)
(Yosi)

 

[Anirban Hazra]

I thought that this would be simple. I converted an SLC program which used IIM instructions (Immediate input) to Compact Logix. The problem is I can't figure out how the Control logix does immediate input data. Perhaps using interrupts? Any ideas?

In CompactLogix there is no IIM instruction because the data from the modules is updated asynchronously to the task execution/logic scan, but you can configure an input as Change of State(COS) that is, the input data will be transferred from the module whenever the specified input transitions from "On to Off" or "Off to On".

 

[(8{)} ( .)]

Thank Anirban.

In order for that to work in a converted application I'd need to have the Inputs update on COS whenever any input changes on/off or off/on.

Any ideas?

Thanks,

(8{)} .)

Yosi

 

[Anirban Hazra]

In order for that to work in a converted application I'd need to have the Inputs update on COS whenever any input changes on/off or off/on.

Yes, exactly!

Suppose "Input_1" is configured as COS and the module has RPI of 700ms.
Then if "Input 1" does not change it's state, updated data will be transmitted from module only every 700ms. But if "Input 1" changes, then updated data of the whole module will be transmitted at that moment itself. Even if you configure only "Input 1" as COS the updated data of all the inputs in the module will be sent immediately when "Input 1" changes.

 

[Ron Beaufort]

it's not that simple ...

Greetings Yosi ...

since CONTROL-logix and COMPACT-logix hardware systems are both programmed using RSLogix5000 software, it's easy to assume that the two hardware platforms operate the same "under the hood" ...

they do not ...

the CONTROL-logix can make use of Change of State ...

the COMPACT-logix can not ...

there can also be differences which come into play based on whether the inputs are LOCAL I/O or REMOTE I/O ...

the important point: the two hardware platforms don't operate the same – so be careful how you proceed ... and the "flow chart" shown in most of the COMPACT-logix books is wrong ...

and be ESPECIALLY careful if you are using periodic tasks – with priorities higher than (lower numbers) seven ... I'll write more later as time permits ...

DISCLAIMER ... this is based on my lab experiments using a COMPACT-logix L35E processor – and RSLogix5000 Version 16... your mileage may vary ... and this is written in haste ... (I apologize in advance for any mistakes) ...

 

[(8{)} ( .)]

Hi Ron!

Haven't heard from you in a while. I'll PM you in a second. Thanks for the input.

Based on what you and Anirban say there is no way to get around this with a Compact logix.

Take care,

(8{)} .)

 

[Anirban Hazra]

the CONTROL-logix can make use of Change of State ...

the COMPACT-logix can not ...

That is strange, because I answered only after referring to the manual(2007 Publication) and as the attached screenshot shows, COS is a part of the I/O Configuration Options.

 

[Anirban Hazra]

DISCLAIMER ... this is based on my lab experiments using a COMPACT-logix L35E processor – and RSLogix5000 Version 16... your mileage may vary ... and this is written in haste ... (I apologize in advance for any mistakes) ...

...that manual includes the Processor on which you experimented and also it is for the same Firmware Revision.

Misleading manuals really sound scary.

So, I would really like to be enlightened as to what the findings of your experiments were as in the future, if I have to work on the same processor, they might help me as well.

 

[(8{)} ( .)]

Hi Ron and Anirban,

The best part of this is I looked into the converted logic. It's an analog mux. If I need it I'll re-write it in 1/2 hour and be done with it. There was note need for immediate inputs in the original program so it's all gone in the trash.

Thanks for your help.

(8{)} .)
(Yosi)