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Maximum number of consistent bytes with SFC14/SFC15.

Created by: Jesper Pedersen at: 6/15/2008 9:43 AM (8 Replies)

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6/15/2008 9:43 AM	Rate (0)
Jesper Pedersen Posts: 279 Rating: (30)	Hi. I am engaging in a heated discussion with afriend regarding how many bytes are consistent when you use SFC14 and SFC15 for transferring data via the DP port on a 313C-2DP. I know about using the process image in stead of SFC14/SFC15, but the question pertains ONLY to SFC14/SFC15. In STEP7 help for SFC14/SFC15, it says that the maximum amount of consistent data is 32 bytes for S7-300. And it says that you should check with each CPU type what it supports. But I cannot find that piece of information in any of the manuals for S7-300. My friend need 128 bytes. I argue that he should switch to using the process image, and he argues that the limitation of 32 bytes was lifted years ago. Who is right ? Where does it say exactly ? If an attempt at using SFC14 or SFC15 is made with a too large amount of datato beconsistent, is an error message returned ? Thanks for any insight in this.
Jesper Pedersen Posts: 279 Rating: (30)
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6/15/2008 1:52 PM	Rate (0)
Zenon_EMEA Posts: 42 Rating: (5)	Hi, here you will find the CPU data, where the maximum consistent bytes are decribed as well in chapter 7 ongoing. Markus S7-300 CPU 31xC and CPU 31x, Technical Specifications
Zenon_EMEA Posts: 42 Rating: (5)
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6/15/2008 5:35 PM	Rate (0)
Jesper Pedersen Posts: 279 Rating: (30)	Hello Zenon_EMEA. In appendix 1.8 it says that the maximum is 128 bytes. I guess then that the online help in STEP7 is wrong. It says plainly that the maximum is 32 bytes with S7-300.
Jesper Pedersen Posts: 279 Rating: (30)
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6/16/2008 7:01 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 1/20/2026 Posts: 12481 Rating: (2722)	Hello Jesper; You will find another confirmation on the 128-byte consistency limit on the newer CPU315-2DP on the following FAQ: http://support.automation.siemens.com/WW/view/en/42413 I found it as part of another thread that is open right now, discussing consistency issues and DP/DP couplers. You might find it interesting: /tf/WW/en/Posts/7970#84674 Hope this helps, Daniel Chartier

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6/16/2008 10:19 PM	Rate (0)
Jesper Pedersen Posts: 279 Rating: (30)	Hi Daniel. The FAQ in the 1st link seems confirm that the limit of consistent data is 128 bytes on the latest genaration of S7-300 CPUs.
Jesper Pedersen Posts: 279 Rating: (30)
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2/6/2018 9:14 AM	Rate (0)
Figura Posts: 19 Rating: (1)	Hello! will answer please.. Functions SFC14 and SFC15 work with simulation (STEP7)???... With real PLC function work, plc1<->plc2... but in similation dont work..
Figura Posts: 19 Rating: (1)
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2/6/2018 9:42 AM	Rate (0)
Duris_I Diamond Member Joined: 4/28/2015 Last visit: 11/27/2025 Posts: 10970 Rating: (844)	Hello, what is known to me, no. There is no possibility communicate with Profibus DP via PLCSIM.
	With best regards... Ivan Duris Flight: OMICO
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2/6/2018 3:37 PM	Rate (0)
Figura Posts: 19 Rating: (1)	i tried use SFC14 and 15 - Profinet, transfer data - dont work.. But then i tried SFB14 and SFB15 plcsim and work transfer data.. sorry for my english
Figura Posts: 19 Rating: (1)	Last edited by: Figura at: 2/6/2018 3:38:28 PM
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2/6/2018 3:40 PM	Rate (0)
Figura Posts: 19 Rating: (1)	yes, i think too, with plcsim sfc14 and 15 dont work
Figura Posts: 19 Rating: (1)
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