7/10/2013 3:50 PM | |
Posts: 378 Rating: (73) |
Dear hdhosseini, Thank you for creating this discussion. Others have already posted above about IEC Timers and I want to say some about S5Time data type. S5Time data type is encoded time values ranging:
Problems: -> We can not use other values except in the above range (e.g we can't use 10s10ms or 1m41s990ms) S5Time Values: S5Time memory uses "16Bit" and the time values are encoded in 4Bit BCD value ranging from 0-999, (see the attached picture taken from S7 help file) [img=400x172]/tf/WW/en/postattachments/download?attachmentId=38322[/img] Wastage of memory area: Now it is not clear for me why not limited to only 999 (=9*100+9*10+9? Since each digit is represented by 4Bit BCD value and in 4Bit it is possible to represent 0-15 (0000 to 1111) therefore it is possible to represent the three digits 15*100+15*10+15=1665 from this case we can have a larger time values range for example: 0ms to 16s650ms ---- in 10ms steps Another unclear point for me is Bit-14 and Bit-15 is irrelevant, why not this bits included to extend time values range?S5Time datatype has "WORD (16Bit)" length but practically it has 14Bit of memory length--- This is another waste of memory. My Conclusion: The number of S5Time values is 999*4+1=3997, but it uses 16Bit memory and in 16Bit we can represent 216 + 1 = 65536 values thus the memory utilization efficiency = 3997/65536 = 6% thus I can coclude that S5Time datatype is 94% wastage of memory . Regards and Thanks all, |
Last edited by: desmul24 at: 7/10/2013 3:53 PM |
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7/10/2013 4:39 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365)
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Dear freinds AMAZINGAHMED ,viralpatel and desmul24 Thank you for sharing your knowledge and experience regarding the topic.About the first cases proposed by "AMAZINGAHMED "and "viralpatel ", I add that as the main topics of concerns here.Mostly in factory automation, you need new features that not be provided by standard tools.Using cyclic interrupts OBs and plus clock memories of CPU recommended by Experts in the forum if there were a strong reason for that (e.g limitation and needed features).To complete this topic,I only provide some previously discussed issue for this cases: 1-Case for using OB3X for generating a simple on-delay timer Timer which does not reset itself2-Case for using clock memories for generating pulse patterns(in SCL) help on SCLCase related to deficiencies in SIMATIC Timer data type introduced by "desmul24" should be checked and compared with TIME data type and will be added soon in the 3rd row. I will rate all posts till my rating Budget re-charged Hamid Hosseini |
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7/14/2013 12:12 AM | |
Posts: 197 Rating: (3) |
Sorry to interrupt such an interesting discussion. But I just noticed some remarks from desmul24under Wastage of memory area: Now it is not clear for me why not limited to only 999 (=9*100+9*10+9? Since each digit is represented by 4Bit BCD value and in 4Bit it is possible to represent 0-15 (0000 to 1111) therefore it is possible to represent the .......................". |
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7/14/2013 5:11 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365)
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Dear Friends, Case related to impressive and detailed introduced by "desmul24" has been checked and will be added as "Deficiencies of SIMATIC TIME data type".Note,We inherited this data type from S5 Timers introduced in 1979,So please consider the limitations from that S5 era.May be in that time it was a great achievement with 16 bit variable.From our point of view from era of fast (64-32 bit) processors, it seems to be a deficiency.Points are listed based on chronology of original post.I do not quote but will mention the case:
We are encountering SIMATIC data type in new controllers SIMATIC S7 1500 only because of people are really accustomed to using this old heritage. Best regards |
Last edited by: hdhosseini at: 7/14/2013 5:29 PMLast edited by: hdhosseini at: 7/14/2013 5:21 PM |
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7/15/2013 12:38 AM | |
Posts: 378 Rating: (73) |
Hello nbk, Thanks for your post The reason I have said "15" instead of "F" is for experession purpose only, It is obvious that there is no such thing 2,3.4 ... 15, or F in "Binarry world" it is a way of representation (saying) and expertly elaborated in the above hdhosseini's post. Thanks again |
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