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Wonderware SCADA and PLC Problems

01/22/2009 6:39 AM

we are using Ac 500 ABB make plc and wonderware make scada system,we are facing communication problem in this system between PLC and scada. we are using MBENET protocol for communicaton.

Can you give me some solution.

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#1

Re: wonderware scada

01/22/2009 6:47 AM

What problems to you have? Look at the Wonderware logger and see if there are any errors. We had problems with MBENET with a Modicon PLC and had to increase the time slice allowed for external communications.

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#2
In reply to #1

Re: wonderware scada

01/22/2009 9:45 AM

This was an interested thread, when you say increase the time slice, do you mean there is scan time issues in the program and/or with the PLC?

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#3
In reply to #2

Re: wonderware scada

01/22/2009 10:24 AM

PLC program execution consists of the following which are continually re-executed

1 . User program execution

2. I/O update

3. External Communications

To keep external communications from hanging the User program execution and I/O update there is normally a configuration parameter that specifies the max time the external communications is allowed to run before releasing the processor to executing the User program and I/O update. This may not be true of all PLC's and Process control controllers but is the norm

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#4
In reply to #1

Re: wonderware scada

01/22/2009 12:25 PM

Isn't timeout the better term? Time slice is quite understandable though.

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#6
In reply to #4

Re: wonderware scada

01/25/2009 2:16 PM

I think I used the correct term.

See the Wikipedia definition below.

Time slice

The period of time for which a process is allowed to run in a preemptive multitasking system is generally called the time slice, or quantum. The scheduler is run once every time slice to choose the next process to run. If the time slice is too short then the scheduler will consume too much processing time.

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#7
In reply to #6

Re: wonderware scada

01/26/2009 9:04 AM

Time Slice is correct for this instance. Certain PLC's dedicate a percentage of each scan interval to certain tasks, and processing requests from Scada / IO Servers is one of them. If you improperly configure (or shall I say, fail to optimize) the time slice, you may not receive all your PLC updates to SCADA. Conversely, if you allocate TOO much of the time slice, then PLC processing might get compromised.

Summary: A PLC scan interval is fixed, and proper care must be taken to ensure all things can be accomplished within that interval.

thx - Rudy

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#8
In reply to #6

Re: wonderware scada

01/26/2009 9:05 AM

I'm sure you're right. And as I said "time slice" is appearing as quite understandable for me anyway. Simply with those brands of PLC, SCADA and OPC i've got used to be working along, I've no met such a term. I recollect I've met "time slice" for PC OS kernel.

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#5

Re: Wonderware SCADA and PLC Problems

01/22/2009 5:32 PM

Harsh -

Can you be more specific about the nature of the problem..? The problem is more likely configuration, but where is the unknown.

In order to save ME from writing a comprehensive thesis on every practical configuration option based on assumptions, please help me help you by giving detailed information about the problem.

Common issues are improper Modbus configuration with regard to block size transfers, etc. I await your response.

Thx - Rudy

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#9

Re: Wonderware SCADA and PLC Problems

08/25/2023 8:14 AM

Start by picking up the phone, and calling <...ABB...>. What happens next is determined by the outcome of that call.

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