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How to pass a STRING into a Function

Created by: s7rookie at: 12/11/2007 11:09 PM (5 Replies)

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12/11/2007 11:09 PM	Rate (0)
s7rookie Posts: 3 Rating: (0)	Hi there, I am trying to pass a String to a Function, but couldn't get the value of the string in the function. Here is what I did: 1. Define a STRING 'FF1234.56RT'in DB1 as test, so DB1.test will contain my string. 2. Create FC1, define i_String as an IN in FC1. 3. In FC1, I have the following codes: L P##i_String // Get the pointer pointing to the first byte of the input string LAR1 // Load AR1 with the address of the first byte of the string L B [AR1,P#1.0] // load the actual length of the string at the second byte T #length // store it in the variable #length T QB 0 4. In OB1, call FC1, i_String:=DB1.test. I get nothing in #length and QB0. But if in FC1, I OPN DB 1 and directly access the string in DB1, everything is fine, but that is not what I want. I need the string to be passed in. There seems to be nothing in i_String. I don't know how the passing in variables in S7 works, but please help!! Thanks!! Attachment String2R.zip (225 Downloads)
s7rookie Posts: 3 Rating: (0)	Last edited by: s7rookie at: 11.12.2007 23:09
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12/12/2007 8:44 AM	Rate (1)
Ates Posts: 198 Rating: (16)	hi, as you can see in the attached pictures when you use fb, your variables are ok and your scripts are working.. in short you can use that kind of pointing logic... when you use fc pointer will point v address which is memory area for fc s (i guess i have no idea actually :) and its not pointing as string length. So you will see blue and red circles in my second screen shot.. when you load string_1 to ar1 it points v 281 when you load string_2 to ar2 it pointsv 287 so length is 6 bytes 2 for db no , 4 for rest .. but it does not transfer actual data in to v area it just sends pointer... so in logic youcan't use itin your logic ... p.s : this just my point of view , i am not surebut TO LET IT WORK quick and go on YOU CAN CHANGE IT TO FB AS I TOLD. Attachment pointing_string_fb_fc.zip (255 Downloads)
Ates Posts: 198 Rating: (16)	Last edited by: Ates at: 12.12.2007 08:44
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12/12/2007 9:16 AM	Rate (1)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 5/16/2023 Posts: 8586 Rating: (1127)	Hello s7rookie, Please have a look in online help of Step7, search for 'Permitted Data Type when transferring Parameters' Perhaps it's useful Alsoare these faq's: http://support.automation.siemens.com/WW/view/en/16848975 http://support.automation.siemens.com/WW/view/en/19106712 Best regards, Wizard

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12/12/2007 11:09 AM	Rate (0)
Ates Posts: 198 Rating: (16)	i found that article very interesting wizard, i tried to point an input... and i couldnt but an in_out yes i could point it... can describe me why ? how are the in and in_out called in different manner by the compiler ? when you point an input it points first byte of its own DI's input for example : if in1 : string_1 lar1 p##string_1 L b[ar1,p#0.0] >>> length of input so it points DIx.dbXx.x if in_out : string_1 lar1 p##string_1 L w[ar1,p#0.0] >>>it will point connected strings db number, so it will point the connection butnot DI .. my question is why is it so ? p.s : btw fcs input is working like fbs in_out ; so if you lar1 it yo can use enteredinputwith that method..
Ates Posts: 198 Rating: (16)
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12/12/2007 7:01 PM	Rate (0)
s7rookie Posts: 3 Rating: (0)	Thanks Ates! I found that a FB will work as well. I really don't know why... Although this makes my program a little more complicated, I guess I will stick to this way...
s7rookie Posts: 3 Rating: (0)
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12/12/2007 7:05 PM	Rate (0)
s7rookie Posts: 3 Rating: (0)	Thanks to Wizard too! I read the same post you sent me. The post seems a little confusing. From what I understand from the post, it indicates that it doesn't matter whether my program is a FC or a FB, but the program calling my program should be a FB, but that didn't work either. So I thought I may missunderstood the post somehow, then changed my program to a FB, and it worked... Still feeling wired. Anyone can explain to us why it is the case? Exactly how are different type of variables be passed into a FC or FB? And any difference between a IN or IN_OUT?
s7rookie Posts: 3 Rating: (0)
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