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String Copy VS Complex INOUT Var

Created by: SOuellet at: 3/13/2012 5:26 PM (10 Replies)

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3/13/2012 5:26 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Hi, I need to copy a String into another String. Here's more detail about my situation (not an actual copy of my project, stripped out for simplicity) I have multiple instances of similar structs, each of them has their own function but they also share one "global" function. UDT1 : STRING_1[24] STRING_A[24] STRING_B[24] DB1: DEVICE_1 UDT1 DEVICE_2 UDT1 FC1 DEVICE_1 : Specific functions for DEVICE_1 FC2 DEVICE_2 : Specific functions for DEVICE_2 FC99 : "Global" Devices Function (where the problem is) So basically both FC1 and FC2 call FC99 by passing their respectice instance of the same UDT as an INOUT parameter. Inside FC99, I can manipulate both instances fine. If I call another function inside FC99, let's say FC100, I need to use basic data type, I can't use my instance (UDT)or a subset of (UDT inside another UDT). How can I copy STRING_A or STRING_B to STRING_1, for example, since STRINGs are a complex datatype? SFC20 does not let me select my INOUT var. LAD / FBD / STL / SCL are fine. My PLC is a S7-315. If you need any more details, I'll be happy to provide them. Thanks for helping me out.
SOuellet Posts: 7 Rating: (3)
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3/14/2012 8:16 AM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	Hi, Look in help system ab out SFC81 "UBLKMOV". There is said that STRING can't be as a parameter, but you can use ANY pointer to point at the string and the only requirement is that lenght must be specified as 1. So it should work for you if you will use pointers.
	Best regards, Darius
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3/14/2012 1:57 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Darius Hi, Look in help system ab out SFC81 "UBLKMOV". There is said that STRING can't be as a parameter, but you can use ANY pointer to point at the string and the only requirement is that lenght must be specified as 1. So it should work for you if you will use pointers. I am sorry but just as with SFC20, my INOUT variable cannot be used as a parameter for SFC81. Hopefully Iunderstand your suggestion correctly. Thanks for replying. Simon O.
SOuellet Posts: 7 Rating: (3)
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3/14/2012 2:13 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 5/2/2023 Posts: 2957 Rating: (242)	Hi, Sorry, but I'm little confused. Maybe you can upload your project here for better understanding ?
	Best regards, Darius
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3/14/2012 3:30 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Hi Darius, here is a stripped down version of my program madewith Step7 5.5. FC1501 is an instance of a "device". This function consists mostly of configuration bits that will be processed in FC1007. (There is more of them and more DBs in my actual project) All devices call FC1007 because they all share some similar functions. The copy part has to be in FC1007, Network #2 (look at the comments) Hopefully this will make things clearer for you. Thank you for your time, I really appreciate your help. Regards Simon O. Attachment String_Copy.zip (75 Downloads)
SOuellet Posts: 7 Rating: (3)
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3/14/2012 3:35 PM	Rate (0)
Nikzitronik Posts: 150 Rating: (17)	Lately I had to deal with string operations in Step7 and I realized that using SCL to perform string manipulation is heaven. I tried to do this using LAD or STL but I thought it was very inefficient. For that reason among other things, I built a simple FC in SCL that moves a string to another string using a single line of code. No need to worry about ANY pointers etc. For example: FUNCTION FC220 :Void VAR_INPUT String_In: STRING[20]; END_VAR VAR_OUTPUT String_out: STRING[20]; END_VAR String_out:=String_In; ; END_FUNCTION The only disadvantage using this method is that in order to use you have to have SCL language installed.
Nikzitronik Posts: 150 Rating: (17)
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3/14/2012 3:56 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Hi Nikzitronik, Thank you for your input. The problem is not really about how to copy a string but rather how to pass a string to a function when this string has been passed as an INOUT parameter to the function calling the other one. I know this can be quite confusing but looking at the example project provided in the post above yours would probably help understanding what my request is. Regards Simon O.
SOuellet Posts: 7 Rating: (3)
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3/14/2012 7:49 PM	Rate (1)
Nikzitronik Posts: 150 Rating: (17)	Sorry SOuellet, I misunderstood your problem. I tottaly see your problem there and I played around a bit and came up with this: FUNCTION FC1008 : VOID VAR_IN_OUT DEVICE: UDT_Command_2_Interlocks; END_VAR DEVICE.COMMAND_A.LABELS.IN_PROGRESS:=DEVICE.HMI_ANIMATION.STATUS; ; END_FUNCTION I havent test it but the compiler does not complain. If it works the problem is that you have to write the rest of the FC logic into SCL. I attach your program with an extra FC, FC1008 with the above SCL code. I also added NW4 in FC1501 so that I can check that I dont get any errors. I hope this helps Regards, Nik Attachment String_c.zip (75 Downloads)
Nikzitronik Posts: 150 Rating: (17)
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This contribution was helpful to 1 thankful Users SOuellet

3/14/2012 8:34 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Hi Nik, while your solution is actually working, my initial request was to have a single network / box / ... inside my FC1007. This way, I can have Ladder logic before / after copying strings and not replace my whole function in SCL. I realize that you got a nice workaround but it's not really what I am looking for since my current customer requires me to have as much ladder as possible. Thank for your time & patience Simon O.
SOuellet Posts: 7 Rating: (3)
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3/14/2012 8:44 PM	Rate (0)
SOuellet Posts: 7 Rating: (3)	Hi again, you just made me think about a real quick workaround : I am going to use your strategy : My FCs are going to call BOTH FC1007 (LAD actual logic)& FC1008 (SCL for strings managementonly)and problemwill besolved. Thanks for enlightening me Simon O.
SOuellet Posts: 7 Rating: (3)
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