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FC's preassigning memory

Created by: MemoGG at: 3/16/2009 6:09 PM (3 Replies)

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3/16/2009 6:09 PM	Rate (0)
MemoGG Advanced Member Joined: 2/20/2009 Last visit: 7/6/2022 Posts: 53 Rating: (0)	Hi Everybody: Something funny is happening when we insert FC's from S5-S7 Converting Blocks (Specifically FC104, FC106, FC107 & FC108). It seems that whenever you insert a block from this library, the system is assigning memory (M, MW, MD) even when you haven´t filled the block parameters (they are still in red) because if you go to reference data you see that there are memory blocks already assigned like when you fill the block parameters. This usually doesn't happen with other FC's. Have you ever seen a behavior like this? Why this happens with certain blocks? Regards

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3/16/2009 11:16 PM	Rate (0)
Phantom75 Posts: 2661 Rating: (279)	Hi MemoGG, Good catch! The blocks you have mentioned (FC104, FC106, FC107 & FC108) do useflag memory in thearea MB200 to MB255. Theonly explanation I can think of is, these blocks were converted from S5. Inthe S5 world it was an "unwritten rule" to use MB200 to MB255 as "scratch flag area" and many standard blocks wereprogrammed using this area.The right way would have been to replace this M area with temp area (S7)during S5 to S7 conversion... Sowhen using blocksfrom theS5-S7 Converting Blocks librarywe should not use flag memory from MB200 to MB255 in our user program. Any memory lower or higher than this area is ok to use. May be we should mark this thread as a tip. Regards
Phantom75 Posts: 2661 Rating: (279)
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3/17/2009 2:50 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 9/16/2024 Posts: 3020 Rating: (1054)	Hallo MemoGG Phantom 75 is right on the money with his advise. To make matters worse, counter 0 (C0) is used by FC81 and FC98. As much asI love the Siemens gear (be it S5 or S7), Siemens did themselves a real disservice by simply converting theseS5 Blocks to S7 (and continue to use the MB200- 255 "scratchflag" area in them) and then provide this library as a "tool" to help with S5 upgrades. My advise is to not use them at all (I never do,never had to andnever will when converting S5 programs). Most of them can also be replaced withwith standard S7 commands (e.g. all the mathematical functionwhich were required and heavily used in 115U systems are no longer needed in an S7). While this does require some manual "clean up" of the original converted logic, the end result is worth the effort (and the customer will appreciate it too). Itrust this helps and good luck with your conversion Cheers Fritz
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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3/25/2009 7:53 PM	Rate (0)
MemoGG Advanced Member Joined: 2/20/2009 Last visit: 7/6/2022 Posts: 53 Rating: (0)	Sorry for the delay to thank your replies. Actually we discover the problem by accident! (many great inventions have been done that way) I agree that if possible it is better not to use those blocks from the s5-s7 conversion library and if it is the last resource, keep in mind the addresses used by them. Regards

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