Siemens CPU318-2 / CP3431-Lean issues

[sigmadelta]

The issue is your offline program occupies 154500 bytes of Load memory (whether RAM or EEPROM).

The 65536 bytes of RAM is not enough storage for the whole program, but the EEPROM has enough (262,144 total).

Any time you download, you are not downloading to the EEPROM, you are downloading to the RAM, and the blocks in RAM supersede the blocks in EEPROM.... but again, there is not enough space in RAM for the download you're trying to do.

 

[benmccormick]

But this is happening even when I am trying to download the program, with no changes, that I uploaded directly from the processor.

I don't understand how it was in there in the first place? Or what has caused the size of the project to substantially increase?

Also, see screenshot, I can no longer upload the hardware, I get an error...

 

[sigmadelta]

So what I recommend is for backup purposes, create a new STEP 7 project, and do the PLC -> Upload Station to PG to have a backup of what's in the CPU right now.

Then switch back to the project you're working with, and do PLC -> Diagnostic/Setting -> Clear/Reset. That's going to clear the RAM and revert back to the contents on the EEPROM.

The issue there is that any process data stored in DBs (data blocks) will also revert back to the original values. The work around for that is to open the uploaded project you just did and download only the DB blocks.

 

[sigmadelta]

Also, see screenshot, I can no longer upload the hardware, I get an error...

Click Details, and post?

Edit: you can continue, it just will be the program without the hardware configuration (code only).

 

[benmccormick]

sigmadelta

With your help I at least seem to have it back to square one, so thank you for that.

I am off for today, but at some point I need to try to get this Ethernet card reconnected and working, but I am very nervous about it now.

Thanks,
Ben

 

[sigmadelta]

The proper way to do it in your specific case, is to write the modified hardware configuration/program to the EEPROM... but... you need a Siemens USB Prommer to do it. I have a USB Prommer, but I'm quite far away from you....

Long story short, the CPU 318-2DP is an odd duck in the S7 family. It's really an S7-400 CPU wrapped in an S7-300 plastic shell. They put less Load RAM on-board than Work memory, which means if you have a bigger program, the only way to expand was adding more Load RAM or Load EEPROM.

Load RAM is backed up by the CPU battery, where as EEPROM is permanent... problem is you have to use a Siemens Prommer to write to the EEPROM. You could buy a RAM module (at least 256kB) and put it in place of the EEPROM, then downloading would be easy, but you have to make sure you CPU battery is always good.

Unless there is a specific reason to stick with the CPU318-2, I'd be inclined to swap it out with a new CPU 315-2DP or CPU315-2PN/DP (or higher CPU) + MMC (micro memory card) to avoid these downloading issues. The MMC is permanent backup like the EEPROM and the new CPUs do not use backup batteries.

Plus, CPU318-2DP are discontinued, so you're basically relegated to ebay to get one if need be.

I could check the feasibility of conversion to a newer S7-300 CPU (or maybe an S7-1500 CPU) if I had your project.

RAM part numbers (check ebay):
6ES7 951-1AH00-0AA0 256KB
6ES7 951-1AJ00-0AA0 512kB
6ES7 951-1AK00-0AA0 1MB
6ES7 951-1AL00-0AA0 2MB

 

[JesperMP]

I think that possibly the problem is the odd nature of the 318 CPU.

The small amount of load RAM is what is available for making online changes. It is a real nuissance on the 318, and on the smaller S7-400 CPUs as well.



The program should fit in the flash memory - 160k needed, 268k available.

But, it is not enough to merely "load" the program as you would normally do with an S7-300, because that attempts to load the program into load RAM, of which there is only 64k available.
You have to use the function "load program to memory card" and then restart the PLC.



You have to be damned sure you have a good backup before you do this !