Memory Consumption

How to calculate the memory consumption of PLC programming.

What do you mean?

1. How much memory is needed in the PC to program the PLC?
   
   This depends on the software used to program the PLC. I wouldn't care too much, unless you're using a really old PC with a memory size as used 4 years or more agoo.
   
2. How much memory does the PLC nee dfor a given program?
   
   Now that's a tricky question, especially since you gave us no parameters to start with. This depends on PLC brand, type and number of instructions used, type and number of variables used and some more I'm forgetting about. Normally you should be able to calculate this if you can answer these questions and you have the specs of the used PLC. Without all that there's no realistic answer possible.[/list=1]
   
   Kind regards,

Thanks for replying, the parameters are as follows


Modicon quantum PLC

700 IO's in which 100 are analogue

total memory available is 550K Approx

Waiting for ur reply

What programming language are you using?

984 Ladder Logic (software is Modsoft or a version of ProWorx)
or
Concept
or
Unity?

One thing you might want to check is if you have to worry
about scan time as well. Unfortunatelly I don't think there is
a magic formula to calculate PLC memory requirements.
It depends a lot on programmer's experience and style.
It also depends a lot on how much data manipulation is required
and what PLC can do (if you have to write something yourself
to increase that functionality).
If the 100 analogue points are 50in/50out and you need to do
50 PIDs it is quite a bit more demanding than just passing
the values to HMI for monitoring (an example). Same is with the
type of logic or if you are trying to log anything (or use
recipes etc.).
Some people can make very small and efficient program while
some will write long and complicated logic that basically
does the same - or even less.

Each instruction requires a certain amount of memory. Somewhere in your programming/user manual there should be data on the execution time and memory necessary for each instruction. The amount of memory and program execution time is totally dependent on your program, so only you can answer that question.

Memory consumption, eh?? Well, first divide into 2 : program memory and data memory. Program memory is quite difficult to calculate while the data memory is quite easy since you know how many internal memory word you use.

There seems to be a lot of modicon post's here recently..I guess most people have realised there 984's are not in support any more..

as for memory..Jim asked the relevent question..Modicon says the quanum line is good for 1 MB (Last time i checked) however its only good for 64K in 984 LL..a big diffence!

let us know what software and what language yoiu are programming in..

D

wow..looked at the date of the posts..How did it come up to the top of the board??

Sorry!!

D

darrenj said:

wow..looked at the date of the posts..How did it come up to the top of the board??

Click to expand...

I'm pretty sure it has to do with a 'member' (term used loosely) replying to old threads with advertising. Phil deletes the post, but the thread remains tagged as 'has a new reply', so it gets bumped to the 'New Posts' list.



-Eric

Belated answer

Example of use Concept 2.5 IEC:
- process the 2000 discrete inputs;
- process the 500 analog inputs;
- freely 50% of memory for CPU 43412A