Siemens S7 Profibus

cjd1965 · May 26, 2011

Hi
I am looking at a spec for a system where I want to use a Siemens S7-300, MP3xx terminal and 6 ET200 slaves all on profibus.

A colleague is adamant that if a ET200 is powered down the main PLC wont detect when it is repowered, and is telling me he has seen it on a previous job

Any advice is welcome

Cheers

Manglemender · May 26, 2011

Sounds like your colleague is remembering S5 behaviour where the CPU builds its address table on power up.

You can program OB86 to handle these events, otherwise the CPU will go into stop.

Nick

Mrslipmat · May 26, 2011

Is there any reason for powering down the ET200 ? As Nick mentioned, you can control OB86 to handle the event in question....

Regards

John

JesperMP · May 26, 2011

Please put the MP panel on ethernet.

In addition to OB86, add OB85 to the project. OB85 triggers when the program tries to access peripherial i/o that is unreachable.

cjd1965 · May 26, 2011

Hi
Jesper
I dont know if ethernet is going to be available (looking into costs), but agreed if it is.

MrSlipMat
The ET200 is located in smaller sub panels that may be isolated for mainenance independantly of the main panel

General
OB86 and OB85..... I realise these are called as error OB's to prevent the CPU faulting .What would be the required code inside these to restore comms. Assume the ET200 is nodes 4,5,6,7,8.

I am looking into code to put into OB85 to generate loss of slave alarms /mimic display

I wont have any hardware for a few weeks to play with so not easy to sort out

Cheers

TurpoUrpo · May 26, 2011

Mrslipmat said:
Is there any reason for powering down the ET200 ? As Nick mentioned, you can control OB86 to handle the event in question....

Regards

John

Power savings, removable device... come to my mind first. Ofc, I would like to hear the reason too.

Manglemender · May 26, 2011

The comms will re-establish on their own.

N.B. There is an SFC for "Parking" slaves but I can't remember which.

Nick

TurpoUrpo · May 26, 2011

cjd1965 said:
Hi

I am looking into code to put into OB85 to generate loss of slave alarms /mimic display

Cheers

There is ready made diagnostics (wincc/wincc flex viz + code for cpu) for profi from siemens, FB126 is current, you can find it on siemens website.

Witch cpu are you going to use?

inst_tech · May 26, 2011

"A colleague is adamant that if a ET200 is powered down the main PLC wont detect when it is repowered, and is telling me he has seen it on a previous job"

I think I'm right in saying if after powering down the slave then you viewed the Hardware Diagnostics, it would be report I/O access errors. When the slave is powered up and the hardware diagnostics updated the message would have cleared. So in answer to your question, the CPU does detect when powered up. (as stated by others the correct OB's would have to be loaded but without any code)

cjd1965 · May 26, 2011

Hi
I thanks for all the advice
Regarding FB126 I looked at this before but couldnt find documentation to say what the DB contents were. I saw something Jesper wrote about Siemens new firmware broke FB126

I am probably going to use a 315-2PNDP ... 2 profi net and 2 profibus ports if funds permit

Jeebs · May 27, 2011

Profibus comms are restored automatically when the slave is detected again.
Use OB86 to detect coming and going of slaves and to make the program act accordingly, alarms etc.
OB85 is triggered when trying to access the I/O's on these 'offline' slaves.
The help (F1) on OB86 is quite clear and has all the information you need to detect which slave has come and gone.

Siemens S7 Profibus

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