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using local data in an FC

Created by: abbeyman at: 9/30/2013 9:56 PM (8 Replies)

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9/30/2013 9:56 PM	Rate (0)
abbeyman Posts: 2 Rating: (0)	Hi, I have a problem using local data in an FC. I defined a local vairable #a1 in FC1 and a#10 in FC10 as shown below: FC1 I1.0 #a1 Q1.0 ----\| \|--------------(N)------------(S) FC10 I10.1 #a10 Q10.0 ----\| \|--------------(N)------------(S) When if try to on/off I1.0 the output bit #a10 in FC2, is the one activated. Hence Q10.0 is set Also if try on/off I10.0 the output bit #a1 in FC1, is the one activated.Hence Q1.0 is set I seem not to be able to work on #a10 & a100 directly inside the FCs. What can i do & why is a local variable in an FC overiding or haviing an influence over another local variable in a different FC?
abbeyman Posts: 2 Rating: (0)	Last edited by: O_Moderator at: 9/30/2013 10:08 PM new subject after splitting from /tf/WW/en/Posts/85551#top
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10/1/2013 4:19 AM	Rate (0)
fritz Diamond Member Joined: 10/7/2005 Last visit: 11/6/2024 Posts: 3026 Rating: (1055)	Hello abbeyman Local data is NOT retentive and "lost" once the FC execution is finished. As such you MUSTinitialise local data (write to it first)before you use it (read from it)and can NOT use it as the falling edge memory bit for your ----(N)---- instruction. The solution is to either use an IN_OUT variable or an M or DB bit. I hope this helps and you'll also find more info on this matter inthe threadIs it ok to use P_Trig instruction in an FC?
	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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1/30/2015 8:02 PM	Rate (0)
consair Posts: 15 Rating: (0)	Dear all, By the way, I also have a problem using Input/Output variable & Output variable in a FC block. I have attached the pdf file of my program below. In my program, I have declared "#Finish" as output parameter and my program is run wrong when I call many FC block. And I am trying to declare it as Input/Ouput variable, my problem was solved. Can someone tell me please what the differences are between input/output variable and output variable in FC? Why my program have a problem when I declare "#Finish" as output? Thanks for your answers! Attachment Compare_time_function.pdf (262 Downloads)
consair Posts: 15 Rating: (0)
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1/30/2015 8:53 PM	Rate (1)
eisenpferdreiter Posts: 1058 Rating: (93)	consair Dear all, By the way, I also have a problem using Input/Output variable & Output variable in a FC block. I have attached the pdf file of my program below. In my program, I have declared "#Finish" as output parameter and my program is run wrong when I call many FC block. And I am trying to declare it as Input/Ouput variable, my problem was solved. Can someone tell me please what the differences are between input/output variable and output variable in FC? Why my program have a problem when I declare "#Finish" as output? Thanks for your answers! Hello consair, in your program you SET #Finish, that means it would be true until it is reset somewhere.But you never rest #Finish. If you declare #Finish as output, you would have to reset it in network 1 by comparing #Temp with 0 and if true then reset #Finish. regards
eisenpferdreiter Posts: 1058 Rating: (93)
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1/31/2015 1:17 AM	Rate (0)
fritz Diamond Member Joined: 10/7/2005 Last visit: 11/6/2024 Posts: 3026 Rating: (1055)	consair Can someone tell me please what the differences are between input/output variable and output variable in FC? Why my program have a problem when I declare "#Finish" as output? Hello consair further to eisenpferdreiteranswer, have a look at the thread FC "out" parameter with DBX for moredetails on why and when FC Outputs can "misbehave" if they are "misprogrammed".
	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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1/31/2015 3:00 AM	Rate (0)
consair Posts: 15 Rating: (0)	Thanks for your helpeisenpferdreiter,fritz Now I really understand it.In the future I will stick to the "Golden Rule".
consair Posts: 15 Rating: (0)
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1/31/2015 4:22 PM	Rate (0)
consair Posts: 15 Rating: (0)	Dearfritz I think I have just understand all of them. But when I tested 2 examples that attached below. I still confuse when use #output parameter in FC block and no longer be confident when use #output parameter. :) I have 2 example: - The first, to caculate running time of pump, I called about 50 times in FC block. I used #Sum_Time(h) and #Sum_Time(m) type #output parameter, it worked wrong. (I solvedwith the change to IN_OUTparameter) - The second, to scale sensor value.I called about 20 times in FC block. It workedbeautifully. It is contrary to my initial forecast. Can you help me why the second example work good? Thanks a lot. Consair90 Attachment Running_Time_Function.pdf (222 Downloads)
consair Posts: 15 Rating: (0)
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1/31/2015 4:24 PM	Rate (0)
consair Posts: 15 Rating: (0)	I am sorry, I attach the first example again When do you often use #output parameter? Can you share it? Regards, Attachment Running_Time_Function.pdf (233 Downloads)
consair Posts: 15 Rating: (0)	Last edited by: consair at: 1/31/2015 5:09 PM
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1/31/2015 6:07 PM	Rate (0)
William_B Posts: 5225 Rating: (1195)	Think of the parameter assignments as follows: INPUT............read only OUTPUT........write only (giving feedback to code that called it) INOUT...........read and write RETURN.......special write only example........................ #V := AddValue(#V1, #V2, #NotZero); where.. #V, #V1 and #V2 as INT #NotZero as BOOL RETURN of AddValue FC as INT
William_B Posts: 5225 Rating: (1195)	Last edited by: William B. at: 2/1/2015 10:43 AM add description for RETURN
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