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memory usage

Created by: 0_Einstein at: 9/22/2010 5:49 AM (8 Replies)

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9/22/2010 5:49 AM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2443)	Ok, so with an S7-1214C, are there options for upgrading available working memory? On our project, we're at 98.5% working memory used. A serious redesign will be required to get the same functionality without any loss in responsiveness. We hesistate to do any of that if we can simply purchase and install more memory. If we can't add memory, it makes sense to wait for the next release of the programming software to see what we can do better with fewer blocks, FBs, FCs, etc. as more things should be included and not require so many custom blocks to accomplish relatively simple tasks. What are your opinions and thoughts on this? I've filled the CPU completely several times, reworked and redesigned to get it down to 98%. I see plenty of room for improvement now that the solution is known. Just do not think it makes sense so close to the release of new software to put much time into it.
	science guy
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9/22/2010 12:35 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	Hi, I'm sorry. Working memory you can't increase. The only possibility you have, is to optimize your program. Maybe this FAQ is a first step to do this: http://support.automation.siemens.com/WW/view/en/41985845

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9/22/2010 2:30 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2443)	Thanks. The technique shown in the FAQ does not say what memory is affected. I have plenty of spare memory, but it is only working memory that is over 98%. How do I design it to use memory with a lower working memory usage? I can see the FAQ help reduce the overall memory consumption footprint. With 2 MB of available memory, how do I use more of that and less of the working memory and get the same functionality? I've used the project resource consumption to see wherethe logic consumes lots of memory and created global DBs for temporary storage of string and other tag types. That helped, but it made writing and debugging the program code more difficult. Guess I'm looking for guidelines for reducing memory consumption above the one item provided in the FAQ. Or, if we wait until the next software release for S7 Basic 11, will there be more tools and blocks that save working memory? Scan time varies from 11-19 ms. I'd also like a much lower scan time though it isn't required. Are there tricks to reduce scan time, like scanning half the logic, solving the I/O, scanning the rest of the logic, solving the I/O? I've seen techniques similar to that used with other control systems.
	science guy
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9/23/2010 1:02 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	Best way is to use jump-instruction and programming a step-chain. There you can left-out some networks, you don't need any time. Especially strings need a lot of working memory. Maybe try to reduce this. If v11 is better, I don't know. I believe there will be no change in this at first steps. So it makes no sense waiting for that. regards

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9/23/2010 2:55 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2443)	Our local Siemens Applications Engineer is visiting on-site next week. I'll relay your comments in hopes we can affect a redesign to improve working memory usage. Yes, strings definitely consume lots of working memory. Trying to pass a string with a max length of 20 to an FC or FB is painful. Outside the FC/FB, you can to CONV the STRING[20] to STRING. Inside the FC/FB you have to use a STRING. Perhaps if the FC/FB allowed STRING[20] to be passed, I could save almost 500 bytes for every string related FC/FB call with a string. Many of my FC/FB calls use multiple string inputs and outputs. Building RS485 messages takes up a bit of space. I'm sure there are more efficient methods, like predefining every possible RS485 message, putting it into a global DB, and calling it up on demand. Had to be faster to process, use less memory, but harder to maintain if we want to add messages later (which I'm sure we will). I see several approaches to reduce the working memory footprint, and knowing it will not be much easier in V11 helps. Will I at least be able to convert between CHAR array and STRING and STRING to CHAR array easily? I had to write a special routine (very CPU intensive) to do those conversions. If it were built in, that would simplify my code as well as reduce the working memory consumption and scan time. Thank you for your comments and suggestions.
	science guy
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9/23/2010 4:36 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2443)	Have not optimized the logic of the programming, but just changing to global DB string[20] instead of FC/FB DB string, saved quite a bit of space. Went from 98+% working memory usage down to 87.7%. That is a rather significant change in just where and how string data is stored and used. Have to be more aware of global strings possibly being used more than once per scan, so the programming can quickly become more complicated. That is enough of a reduction for now. Thanks again!
	Last edited by: huggy_d1 at: 9/23/2010 4:37 PM Corrected typo science guy
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9/27/2010 2:36 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	Will I at least be able to convert between CHAR array and STRING and STRING to CHAR array easily? Do you know FieldRead/FieldWrite instructions? This is the easiest way to do that. http://support.automation.siemens.com/WW/view/en/40651586 Edit: Sorry, my fault. It isn't possible directly. I think they made some changes. But if you take an array of char, it should work.
	Last edited by: Robster at: 9/27/2010 2:46 PM
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9/27/2010 2:59 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2443)	Yes, I used those special function blocks to build char array from strings and strings from char arrays. There might be a better way, but I basically walked through the array and concat the char to the output string in a FB. Did some preliminary tests to verify my output string was long enough, my input was not nil, etc. Same for string-> char array. It would be nice if the CONV command actually did this automatically, or I could simply point to the char array that starts two bytes after the pointer to the string.... Then build a string from a char array is easy. Copy the char array to the string pointer + 2, set the actual len to num chars copied, and done. String handling is very limiting with the S7-1200 because of strict type checking. If it were possible to turn it off, that would be nice. Also, passing a string with length less than 255 to an FC/FB requires conversion to a full string. Wasteful of memory and requires extra steps to coerce strings to STRING (from say STRING[20]) before and back to STRING[20] from STRING afterwards. Consumes lots of extra memory. Is it possible to get an advance copy of the release notes for V11 so we know what is added and changed so we know what to stop trying to improve? Would help target our efforts if we know what gets really easy with V11 by simply upgrading. :)
	science guy
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9/27/2010 3:31 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 10/23/2024 Posts: 1343 Rating: (141)	No sorry, you have to wait until v11 is published. There are no pre-released. At the moment we're all waiting with big expectation of it.

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