uptown47
Lifetime Supporting Member
Hi all,
I was always under the impression that S7 300 series PLCs needed a MMC card to function. Therefore when you download a program it is going on to the MMC. If you then remove the MMC and put it into a different PLC it would transfer the software (and hardware config etc).
However, one of our guys reported to me a strange occurrence..
He wanted to do a memory reset of the PLC in order to try and clear a persistent fault.
He compared the blocks and found that he had identical software on his PC as the PLC.
He then performed a 'memory reset' (something which I have always thought deletes / formats the contents of the MMC).
He then said that when he completed the memory reset and did a comparison of the software, the blocks in the PLC were vastly different and seemed to be from an old program?
He managed to fix it by simply downloading all the offline blocks into the PLC but I just wondered how/if this is possible?
Is there a program on the MMC and a program stored somewhere in the PLC as well? I've seen the options in the memory to "copy from ROM to RAM" etc and wondered if there was a retentive area in the PLC that could have been harbouring an old copy of the software somehow?
Many thanks for clarifying how this set up works?
I always thought the copy ROM to RAM was a throwback to when the PLCs had EEPROMs in them?
Any ideas?
I was always under the impression that S7 300 series PLCs needed a MMC card to function. Therefore when you download a program it is going on to the MMC. If you then remove the MMC and put it into a different PLC it would transfer the software (and hardware config etc).
However, one of our guys reported to me a strange occurrence..
He wanted to do a memory reset of the PLC in order to try and clear a persistent fault.
He compared the blocks and found that he had identical software on his PC as the PLC.
He then performed a 'memory reset' (something which I have always thought deletes / formats the contents of the MMC).
He then said that when he completed the memory reset and did a comparison of the software, the blocks in the PLC were vastly different and seemed to be from an old program?
He managed to fix it by simply downloading all the offline blocks into the PLC but I just wondered how/if this is possible?
Is there a program on the MMC and a program stored somewhere in the PLC as well? I've seen the options in the memory to "copy from ROM to RAM" etc and wondered if there was a retentive area in the PLC that could have been harbouring an old copy of the software somehow?
Many thanks for clarifying how this set up works?
I always thought the copy ROM to RAM was a throwback to when the PLCs had EEPROMs in them?
Any ideas?