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CPU selection from Input outputs

Created by: john Enthu at: 5/1/2008 11:42 AM (6 Replies)

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5/1/2008 11:42 AM	Rate (0)
john Enthu Posts: 69 Rating: (0)	Dear Sir, What is the basic criteria to calculate the working memory required in CPUfor the given input outputs? This will help us whenever any new system needs to design, we can be able to select best CPU from S7-300/400.
john Enthu Posts: 69 Rating: (0)
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5/1/2008 6:07 PM	Rate (0)
Phantom75 Posts: 2661 Rating: (279)	John: I have not come across a single Excel table that gives you a direct correlation between I/O's and CPU selection. There are other criteria beside I/O count (like response time/communication load etc.) that should be taken in to account for CPU selection. Perhaps the following entries will help: S7-300 CPU 31xC and CPU 31x, Technical Specifications http://support.automation.siemens.com/WW/view/en/12996906 Differing information on the requirement of offline/ online memory http://support.automation.siemens.com/WW/view/en/13962087 regards
Phantom75 Posts: 2661 Rating: (279)
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This contribution was helpful to 1 thankful Users Diniz_

5/1/2008 6:22 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 12/9/2025 Posts: 2957 Rating: (243)	Hi, I can tell you from my experience that I/O count have not very much impact on working memory used. The main thing is algorithm which you will use to handle these I/O. You may have very complex algorithm with lots of FB and DB used and handle not very much I/O andd you would use much of working memory. In other hand you may have lots of I/O, but handle in the way like: A I0.0 =Q0.0 In that case you will use not very much working memory. So there is no direct connection between number of I/O and working memory used. Regards,
	Best regards, Darius
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5/1/2008 7:30 PM	Rate (0)
Phantom75 Posts: 2661 Rating: (279)	Darius: You have explained this in a very clear way and I absolutely agree with you! Regards
Phantom75 Posts: 2661 Rating: (279)
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5/2/2008 1:17 PM	Rate (0)
Denilson Pegaia Diamond Member Joined: 9/23/2005 Last visit: 12/11/2025 Posts: 4411 Rating: (1487)	Hi, The number of instructions for each IO point depends of the many factores: tecnology (machine, plant,et), library and standards used, experiences of the programer, tool (PCS7, CFC, SCL, LAD, STL, etc), etc. Any general aproach many cause very large imprecisions. I suggest you do yourself your standard . Do somoe configurations, and looks how many bytes them takes. There is a general calculator in the Siemens online catalog: https://mall.automation.siemens.com/DE/guest/index.asp?aktPrim=0&lang=en
	Denilson Pegaia Siemens Industry Sector Technical Support
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1/25/2018 12:53 AM	Rate (0)
APKV2 Regular Member Joined: 9/3/2014 Last visit: 9/25/2025 Posts: 9 Rating: (0)	Pegaia Hi, The number of instructions for each IO point depends of the many factores: tecnology (machine, plant,et), library and standards used, experiences of the programer, tool (PCS7, CFC, SCL, LAD, STL, etc), etc. Any general aproach many cause very large imprecisions. I suggest you do yourself your standard . Do somoe configurations, and looks how many bytes them takes. There is a general calculator in the Siemens online catalog: https://mall.automation.siemens.com/DE/guest/index.asp?aktPrim=0&lang=en Dear, The link https://mall.automation.siemens.com/DE/guest/index.asp?aktPrim=0&lang=en, is not working. Will you please check the link

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1/30/2018 6:37 AM	Rate (0)
8Noodles Posts: 1086 Rating: (53)	Hi APKV, I think this link can help you: https://mall.industry.siemens.com/mall/en/ww/catalog/products/5000013?activeTab=configurator&regionUrl=WW Best regards, Noodles
8Noodles Posts: 1086 Rating: (53)
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