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SIMATIC S5 / STEP 5

EPROM & PLC Memory Containing Different Programs

Thread Starter: nevaland Started: 6/16/2012 7:05 PM Replies: 5

6/16/2012, 7:05 PM

nevaland

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Hello All,

I'm at a site with S5 115U 944 CPU containing EPROM (not EEPROM!) with old program, i dont have an UV Eraser, so now I intend to transfer the new program into the PLC memory directly. With the battery installed (hence retaining the PLC RAM contents in the event of power cycle), what can be the consequences if the old program is still stored on EPROM and new program is running in the PLC memory?

I know, that in the case of total power loss, on restart the PLC memory will be overwritten with the old program still residing on EPROM. But can they run aside (two different programs) if every thing is normal? My question is that.

Regards,

Nevaland

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6/17/2012, 10:46 AM

fritz

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nevaland wrote:

But can they run aside (two different programs) if every thing is normal?

Hello nevaland

Yes you can have a different program in the RAM in a 944 CPU and it will be executed irrespective of what's in the EPROM.

Have a look at the S5-115U Programmable Controller manual for more on this.

I hope this helps

Cheers

fritz

The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited.
To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.

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6/17/2012, 10:19 PM

nevaland

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Thanks fritz!

I recently heard a local Siemens employee saying that when using the external USB programmer you don't need to erase the EPROM, when programming, it automatically erases the existing program on the EPROM and you don't need the UV eraser (which I highly doubt its possible that way), can you confirm?

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6/17/2012, 11:41 PM

fritz

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Hello nevaland

I'm afraid to say I can NOT confirm this and wonder if there was a misunderstanding.
Perhaps the Siemens employee understood that you have an EEPROM (Electrically Eraseable PROM) in which case a UV light does nothing and it can be erased only Electrically (e.g. via an external USB programmer or a Siemens PG).

An EPROM however can only be erased via a UV light as far as I know (apart from taking the EPROM's chip window cover off, leaving it exposed to sunlight for a few days and keeping your fingers crossed).

I hope this helps

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Thank you for this post from:

nevaland

6/20/2012, 7:52 PM

nevaland

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Hey fritz! I'm also of that opinion that EPROM's can only be erased through UV and cannot be overwritten through blowing if a program is already residing on it (since I've worked on EPROM's before in the microcontroller era though not on S5) this was also verified by Siemens tech support when I asked them.

Guess I have to hunt for a UV lamp in the middle of nowhere! :D

Thanks a lot for your interest. Cheers!

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6/21/2012, 12:06 AM

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