11/18/2013 6:56 PM | |
Posts: 2 Rating: (0) |
I would like to know the size of the L-Stack for the CPU319F-3 PN/DP PLC, order number (6ES7318-3FL01-0AB0). I need to know the maximum length per priority class and the maximum per block allowed in this processor. I am asking because I am confused after looking through the documentation. Below I detail where I have looked for this information, what I have found, and why I am confused. The first place I looked is directly on the specifications: http://support.automation.siemens.com/WW/view/en/36816541/td From the specs: Local data:per priority class, max.32768 byte; Max. 2048 bytes per block From this I presume that each priority class has 32KB and I get 2KB max per block. Knowing these values is critical for me so I want to confirm they are right. I read a FAQ on S7-300 CPU 31x -- Product information -- Background and system information: http://support.automation.siemens.com/WW/view/en/291495 Here it states that: "The L-stack is used by the CPU for internal processing. The STL editor itself also uses bytes of local data, e.g. in transferring parameters for a block call. Note: 256 bytes per priority class are provided per program processing level (run level). - for S7-300, fixed - for S7-400, usually can be set under ”CPU Properties” in the hardware configuration" This is confusing for me. I am familiar with the ability of the S7-400 CPUs to have the L-stack configurable, but from what I understand this FAQ is stating that there is some sort of limitation of 256 bytes on the L-stack for s7-300 PLCs. It states that it is per processing level, what does this mean? I acknowledge that this FAQ was written in 1998, perhaps the L-stack is now larger in these CPUs and the 256 bytes is now increased to 2048 bytes. I have checked the forums here and have found a thread closely related: http://www.automation.siemens.com/CN/tf/WW/en/Posts/19265 Here the size of the L-stack was answered to be: “Local Stack: S7 CPUs change to STOP mode if the permitted L stack size for a program is exceeded. This is extracted from the manual Simatic CPU 31xC and CPU 31x, Technical data.” I searched for this manual on this website but did not find this information, the closest I found was, From Ref Manual: S7-300 CPU 31xC and CPU 31x: Technical specifications Manual A5E00105475-12 (03/2011) http://support.automation.siemens.com/WW/view/en/12996906 but in Chapter 9, it confirms that the local data for all 300 series PLCs is: Local data - Per priority class, max. 32 KB per execution level, 2 KB per block. Upon looking on the web I found this data in an older version of the specification, from 2003: http://www.fer.unizg.hr/_download/repository/S7-300_CPU_Specification.pdf which has the data about the smaller L-stacks. So in the end I am confused. The recent manuals and specifications all state that I will have 32KB of L-stack for each priority class and 2kB max per block. An older FAQ tells of another parameter which I do not understand, which is the 256 byte limit. An older specification manual tells of smaller L-stacks. I would appreciate if someone could let me know what this FAQ is speaking about, if it is outdated or still relevant. Does anybody know if the L-stack size in these processors has increased through the years? Can anyone confirm that s7-300 series PLCs have 32KB of L-stack per priority class and 2KB per block max with no further limitations? |
Last edited by: Mhurajt at: 11/18/2013 7:05 PM |
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11/20/2013 7:41 AM | |
Joined: 10/7/2005 Last visit: 9/25/2024 Posts: 3022 Rating: (1054)
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Hello Mhurajt nicely researched I must say but in the end you would have possibly been better off just checking the technical specification of the CPU model that you intend to use. S7-300's have been around since the mid 90's and essentially now exist in their 3rd generation (firmware V3.x). Their performance has greatly improved over the years, not only as far as L-Stack size is concerned, but also processing speed, work memory, communication capabilities (e.g. onboard Profinet port and more connection resources), address range, inbuilt SFC's and SFB'sand so forth. Even though you still can't change the size of the L-stack in them, you need to trust the spec of of your 319F-3 PN/DP CPU (6ES7318-3FL01-0AB0), it will have 32kB of local data per priority class and supports up to 2kb max per block (which should be more than you could possible need, I hope). I hope this helps |
Cheers |
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