s7-400 memory bottle-neck

Hi
Iam using an s7-400 plc, but every time I try to download a db, or a more than one fc for example I get an error saying that 'there is a potential memory bottle neck do i want to continue', so i click 'yes' but it then comes back and tells me the operation had to be aborted. when i open module info and look at memory it says its 97% full and it wont compress any further. I cannot perform any program changes because i cannot download to the plc, can anyone help me. Im hoping that there is a simple solution to this but unfortunatley i'm used to using modicon plcs and this is my first siemens experience.
Thanks
Clarke

Clarke

How big is your program? Is it that big that it will take up 97% of the available memory in your PLC?

Probably not.

A full memory reset will probably solve this problem, to perform a memory reset do the following:-

Hold the mode selector switch in the MRES position for at least 3 seconds then release it, then after a maximum of 3 seconds hold it in the MRES position again for at least 3 seconds.

This will return the CPU to all default settings apart from the MPI address, this is so that you can still communicate with it using MPI. If there is a memory card fitted with the user program on it, the CPU will read this card and load the user program from it.

I know with S5 PLC's that when you delete a block, it isn't actually deleted, it is marked as void, thus a lot of deleting and adding of blocks can quickly use up available memory, not sure if this applies to S7 PLC's as well.

Paul

Totally unqualified to answer this (only started using S7300 yesterday for the first time!) - but here goes anyway.......

First time i attempted to download to the CPU315-2DP, i got the very same message. Then realised that it NEEDED the Micro Memory Card inserted (even to download just a couple of rungs!) . Not sure if the 400's even have an MMC - but thought i'd mention it.

All very new to me, and still on the 'painful' learning curve.....(much happier with the ole AB stuff) - but getting there.

Clark, what kind of memory card are you using (if any)? If you aren't using a memory card at all, then your program will fill up the onboard ram pretty quickly, which is why compressing won't help.

S7-400 bottlenck

Your problem isn't that your program is too big for the CPU. The problem is as follows.

You said you have used 97% of the memspace. That means that the largest block you can dowload has to be smaller than the 3% that is left of the memspace. For ex. if your total memspace is 32kB and your program is in total 30kB. Then a single FB/FC/DB has to be smaller than 2 kB otherwise the download will be rejected. The solution is, use the menu command "Display accessible nodes". Open up the "Blocks" folder and delete all files. No there aren't any posibility to erase the SFC's or the SFB's. Close after finished and download the whole project from the SIMATIC Manager. Now it should be working. If your live at a running machine. Your changes has to be applied at next stop of the machine.

Just a thought: S7 will not compress memory while you are monitoring anything.

You can also request memory compression from the 'Module Information' dialog.

" Iam using an s7-400 plc,"
"when i open module info and look at memory it says its 97% full "

are you really using a 400; or is it a 300 ?

anyhow, in the module information, where it says 97% full, you also get a reading for the free load memory; and free work memory

any block that is bigger than this 'free load mem' or 'free work mem' cannot be loaded : the memory is too small.

a little work-around : maybe you can 'temp.' delete a block in the plc; then load the block which is to big; and the reload the deleted block.


but consider using a bigger memory