User Memory of Allen Bradley...?

[Mr_B]

Wot is the "user memory" of a PLC controller? I mean like wot does it mean? Not how much it is? For instance Control Logix 1756-L55M12 is 750kb. What does that tell u in Layman's terms...

 

[elevmike]

User memory is data memory, such as "ram" would be in a PC, that could be used for collecting, storing and manipulating data.

There is program memory that retains your PLC program, User memory, Counter & timer memory, Then the memory used to retain the instruction set (rom) etc..

 

[Mr_B]

So how will I know wot size UserMemory I wud need for a controller?

 

[elevmike]

Mr. B,

Scroll to the very top of this page and click on "Learn PLCs".

 

[mgvol]

For determining memory requirements for a ControLogix CPU, go to this link and reference the table at the top of page 41:

http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1756-sg001_-en-p.pdf

This is should only be used to determine memory for AB's 1756 CPU's; the Logix platform is vastly different from all other PLC's, thus the need for this type of memory calc. The CompactLogix memeory is determined the same way, but some of the values are different.

 

[MartB]

If you are using RSLogix 5000 you can get an estimate of the memory size you will need for a particular plc, it's a built in function to the software.
Select your controller plc, right click, select properties, select the memory tab, hit the estimate button.
Of course this is only useful if your program is pretty much complete.

 

[Mr_B]

Mr. B,

Scroll to the very top of this page and click on "Learn PLCs".

u're wasting u're time dude.........

 

[Mr_B]

thanx a fooken million mgvol... u were extremely helpfull!!!!



BTW some ppl can learn a thing or 2 from u...:site:

 

[Mr_B]

Please define wot is "Controller Tasks"....

 

[GMc]

If scrolling to the top of the page and clicking "Learn PLC's" like elevmike mentioned is wasting your time then why should anyone waste there time answering your homework questions.

Gary

 

[elevmike]

u're wasting u're time dude.........

Thanks for letting me know; I'll try & remember that next time I see a thread started by you...

 

[Mr_B]

There's too many arrogant guys on this forum. U always asume 1 that ask a question is some lazy bum student who party'd 2 much and now wants other ppl 2 do his homework!!!!!!!! Wots up with that?

The link mgvol gave me was very useful... why don u try and do the same.

And BTW Gary... with the help u're worth it wud prolly be better if u don waste u're time to giv me wise@ss answers.

elevmike, I did not mean 2 offend u but u came out was arrogant. So if I did offend u... I apologise...

 

[Lancie1]

Mr B,

Elevator Mike is known here for helping others, not being arrogant. His advice to you was very sound. If you had gone to "Learn PLCs", then clicked on "The Internals", you would have seen a diagram that shows the very memory that you asked about.

From your questions, we can tell your level of knowledge. My question now is, "Do you have enough knowledge to understand the information on "Learn PLCS"?", or should you start at a lower level?

(1)As has been pointed out, so-called User Memory is that part of CPU memory that is set aside for use by the user, where Program Memory is reserved for use by the CPU (microprocessor) to store the program and other information used by the CPU.

(2)To calculate the size of User Memory you need, you have to add up all the different requirements of your program. Each ladder rung takes X bytes. Each Input and Output takes X bytes. Each subroutine takes X bytes. Each memory variable (timers, counters, integers, floating numbers, binary numbers, and so on) takes X bytes of memory. Your manuals will give the requirements for each one. Do most of us do this for every project? No, we know from experience approximately what size CPU will be needed for a given program. I have only ran out of user memory 1 time in 30 years, and that was for a program that had 10 inputs and 1 analog output.

(3)Controller tasks refers to the operations performed by the Central Processing Unit (CPU, or the microprocessor), which is the "controller", or brain, in a Programmable Logic Controller. Controller tasks cover a wide range of activities, but the basic processor cycle is very small. Again, refer to "Learn PLCS" ("How It Works") on this site. It consists of only 3 steps: Load Data, Perform Operation, Save Results to Memory. This becomes the scan cycle that Phil Melore mentions in "Learn PLCS".

ALso Mr. B, would you please learn to spell "would", "what", "you are", and a few other English words? It would help to prevent irritation if you could get closer to the right spelling. You may use a spell checker program to help you out with this task.

 

[Bob O]

Mr B,

I thought Mike was being helpful but by your comments it appears you don’t feel the same way. And with your last comment I think I will also ignore your threads. Not that it’s a big loss to you, but you never know.

Bob O.

 

[Mr_B]

All arrogant...

Lankie 1 ... u can tell my knowledge... good for u ... u think I would b on this site if I understood all about PLC's...

and about the spelling... wud, cud, abt, shud, wot, u are all abrev's...

U so wise, y didn't u figure that one out... huh...

U do that Bob... and all u're (that's 4 u Lankie1) friends. There r ppl that will help. If not then so b it. It's better than to always be "belittled" by arrogant______'s( use your imagination).

ps: is it a coinsidence that all of u hav the same flag....hmmmm I think not... typical.

Once again... I apologise to elevmike