Siemens S7-1200 Work Memory

exiled · Jan 22, 2020

Hi Guys,

Is there any way of compressing the "Work Memory" of a Siemens S7 1200 CPU.

I did change the installed card from a 4mb to a 12mb. I didn't realise the work memory was on the cpu. Am I right in thinking this is CPU RAM?

Any advice welcome.

kalabdel · Jan 22, 2020

Yes it's analogous to RAM that it is volatile memory.
Double click on program info in the project tree to see how the memory is used and have a look at this thread.

mk42 · Jan 23, 2020

I don't think there is a "Compress" function like there is in an S7-400.

You could potentially try factory resetting the PLC and downloading again, but I'm not sure how much it would help.

I THINK that the PLC gets "compressed" whenever you reinitialize the DBs, but I'm not sure.

JRW · Jan 23, 2020

Please tell us you didn’t buy a 1211 and are trying to do recipes etc etc etc

exiled · Jan 26, 2020

The plc is a 1214C. We did have to add a CP module a few years back and I must admit this looks like where all the work memory is been used.

Just wondered if you guys knew any work arounds.

JRW said:
Please tell us you didn’t buy a 1211 and are trying to do recipes etc etc etc

What do you suggest I put in its place a LOGO?

kalabdel · Jan 26, 2020

Double click on program info in the project tree and post a screenshot of it.

PLC · Jan 26, 2020

Post 4 is referring to data blocks...
If you are using many or large data blocks, there are some tricks loading back and forth from load memory to work. This saves memory.
Is this your case?
Post 6 should also tell us this

exiled · Jan 27, 2020

Hi guys
Please see attached image of data usage.

Let me know if you want it drilling down further

Lare · Jan 27, 2020

You need to compress program or change bigger CPU.

Since FB's are multiused, I would think that it would be easier to check FC side if there is same FC -blocks which could be changed to FB/DB and save little bit memory.

Also Karnaught mappping and ST-coding helps save memory.

And if there is calculations, maybe you can change them so that not all is calculated on same program scan.

Would it use then less work memory, since not all code is executed at one scan cycle

Easiest would be change to bigger 1200 or 1512 CPU series

exiled · Jan 28, 2020

Lare said:
You need to compress program or change bigger CPU.

Since FB's are multiused, I would think that it would be easier to check FC side if there is same FC -blocks which could be changed to FB/DB and save little bit memory.

Also Karnaught mappping and ST-coding helps save memory.

And if there is calculations, maybe you can change them so that not all is calculated on same program scan.
Would it use then less work memory, since not all code is executed at one scan cycle

Easiest would be change to bigger 1200 or 1512 CPU series

I think it would be difficult to convince the customer to upgrade the cpu as its been in for a few years now. I have started to condense the program by removing functions that they don't use etc.

Interested in moving some maths around. what is the theory behind that?

TIA

kalabdel · Jan 28, 2020

exiled said:
I think it would be difficult to convince the customer to upgrade the cpu as its been in for a few years now.

I was going to ask earlier about you considering a LOGO!!! Didn't quite get that.

What is the PLC firmware and are there processes that can be moved to an I-Device perhaps with some of the modules?

Lare · Jan 28, 2020

exiled said:
Interested in moving some maths around. what is the theory behind that?

TIA

Work memory is where PLC runs programs, not sure if all blocks are moved to work memory at once, or is it optimized only for blocks which are needed.

At least dividing maths to several scans can make program scan faster.
Anyway, it is nowadays usually not needed, as CPUs have better performance than many years or decades ago.

kalabdel · Jan 29, 2020

Here's how much Sinamics blocks starting from TIA versions 13,14 and 15. I don't know what version of the blocks you are using but you got pretty good memory for them.

Edit: File is too large.

exiled · Feb 1, 2020

The CPU fw is 4.1 and the project is written in V13 and as suspected the customer wont upgrade the cpu.

So i've been experimenting by removing some functions that they don't use to try and condense the program with some success.

I decided to do another experiment with version upgrades. going from V13 to V14 makes a huge difference. So i think this will be the easiest way to go with no loss in functionality.

Moving on I think we should be using a 1500 instead of the 1200 platform

janner_10 · Feb 2, 2020

exiled said:
The CPU fw is 4.1 and the project is written in V13 and as suspected the customer wont upgrade the cpu.

Surely thats cheaper than paying for your time trying to cram extras into a plc that is undersized.

A 1215 lists at £545, minus 25% or so is £400, spend a morning on it and its cheaper to just get a new plc, with a bit of headroom for future proofing.

Siemens S7-1200 Work Memory

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