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Text string problem

Created by: vidarv at: 8/9/2006 10:52 AM (6 Replies)

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8/9/2006 10:52 AM	Rate (0)
vidarv Posts: 66 Rating: (1)	Hia all! The goal is to write a text value to a tag (type string [20]) ina DB in myPLC, the text value will be changing, both value and length. Tag in WinCC is defined as a text tag 8-bit character set. I have tested this by using an I/O field in WinCC and the value is transferred to the tag in the DB, but problems appear if the length of the last input is shorter than the input before because the end of that input is still in the DB. Example: First input abcd =>value in tag (type string[20]) in DB is abcd Next input efg => =>value in tag (type string[20]) in DB is efgd, (should be only efg) Can anyone help! Best regards V
vidarv Posts: 66 Rating: (1)
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8/9/2006 11:08 AM	Rate (0)
Ikkezelf Posts: 1084 Rating: (72)	Hi, Write the closing argument as well. \0 So whenyou input the second text efg make sure you add \0 and therefore write efg\0 into the Tag.
Ikkezelf Posts: 1084 Rating: (72)
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8/11/2006 3:15 PM	Rate (0)
vidarv Posts: 66 Rating: (1)	Thnak you, but still a bit lost, how do I add \0 into the Tag? An example would be great!
vidarv Posts: 66 Rating: (1)	Last edited by: vidarv at: 8/11/2006 3:15 PM
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8/14/2006 9:16 PM	Rate (0)
vidarv Posts: 66 Rating: (1)	Anyone ? I'm a bit lost, probably stupid![:blush:] How do I add \0 to a Tag ? VBS script? abcd =>value in a text tag 8-bit character set. in winCC :Tag1 Tag 1 is to be transferred to a second tag Tag2 (type string[20]) in a DB in my PLC. Next action is input of efg into Tag1 then this value is transferred to Tag2, value in Tag2 (type string[20]) in DB is efgd, (should be only efg), I need to overwrite the remains from the first transfere! An example would be great!
vidarv Posts: 66 Rating: (1)	Last edited by: vidarv at: 8/14/2006 9:35 PM Last edited by: vidarv at: 8/14/2006 9:24 PM
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8/15/2006 10:15 AM	Rate (0)
Salma Gold Member Joined: 9/27/2005 Last visit: 11/27/2007 Posts: 1398 Rating: (151)	OK I have done some testing and get the same results as you. I then did some investigating... First, please read this faq http://support.automation.siemens.com/WW/view/en/7508664 So : the 1st byte of a string contains the maximum allowed value the 2nd byte shows the actual value. WinCC correctly reads these two administration bytes to determine the current string length and ignores older values. I think your program needs to do the same. Maybe someone in the S7 forum can tell you how to do this in your Step7 program. Otherwise you would have to pad trailing zeroes onto the end of your string, but this sounds like bad programming to me. I hope this makes sense, if not just ask.

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8/15/2006 10:24 AM	Rate (0)
vidarv Posts: 66 Rating: (1)	Hia! Thank you for your effort salma! What I have done is to add a number of space entries (Tag1 + " ") to my string in a VBS script , this works, but in my opinion not to good programming. Maybe I should try the S7 forum!
vidarv Posts: 66 Rating: (1)
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8/15/2006 10:41 AM	Rate (0)
Salma Gold Member Joined: 9/27/2005 Last visit: 11/27/2007 Posts: 1398 Rating: (151)	Maybe this FAQ will help http://support.automation.siemens.com/WW/view/en/10913338get you started

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