Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Block Move from Array of byte to String

Created by: zerocool3 at: 2/12/2013 1:42 PM (2 Replies)

Rating (0)

Thanks 1

3 Entries

2/12/2013 1:42 PM	Rate (0)
zerocool3 Posts: 4 Rating: (0)	Dear, I'm working on a program where data is read into a DB-block as a array of byte. Next i would like to be able to move the data in the same DB- to different place and with the data type string. So far i'm doing this by using a block move (i'll add a pdf with some pictures to help explain the situation). This works but i always seem to lose the first 2 bytes (letters) when converting. If the data read in should be 'SIEMENS' i'll find the S and I in byte 0 and 1 in the array, but when converting to string it will just show 'EMENS'. See pictures for example. Does anyone have a better method for this? Is this a bug or am i doing something wrong? thank you for your help. ps:Used plc is a S7-300 so the instruction Chars_TO_strg isn't an option Attachment Siemens Forum 12_2.pdf (1308 Downloads)
zerocool3 Posts: 4 Rating: (0)	Last edited by: zerocool3 at: 2/12/2013 2:06 PM Last edited by: zerocool3 at: 2/12/2013 2:05 PM
Suggestion To thank Quote Answer

2/12/2013 3:23 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/19/2024 Posts: 15207 Rating: (2417)	In Step 7, strings are represented by a bunch of bytes with a structure like this: max length [default for :string = 254] length [actual number of characters in string, like 'here' = 4] array of char holding the values. For the 'here' as a string[254]: byte 0 = 254 byte 1 = 4 byte 2..5 = 'here' bytes6..254 = not observed You will want to use absolute addressing for your string. Let's assume your string tag the first tag in your DB: DB1.DBB0 = 254 DB1.DBB1 = 4 Then push your block move to P#DB1.DBX2.0 There are probably better ways, but this explains what happens in the background. I think many would run the character array into an FB, then use the AT overlay to help create the string more easily.
	science guy
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users cmattson

2/16/2017 1:54 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4767 Rating: (123)	New question published by nghia.cuong93 is split to a separate thread with the subject Move string variable. Best regards Min_Moderator

Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on