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Manage bit of byte

Created by: sbartoc at: 5/2/2014 11:23 AM (8 Replies)

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5/2/2014 11:23 AM	Rate (0)
sbartoc Bronze Member Joined: 3/3/2014 Last visit: 3/20/2023 Posts: 221 Rating: (8)	Hello everyone, Is Possible to take some "bit" of a byte and then save it? I mean if a have a byte like this 0 0 1 0 0 0 0 0 0 0 0 1 1 1 1 1 , how can I take the last four and save it in a variable? then i want to represent in hex and take the ascii code, but this is an other problem. First I have to understand how to do the first "step". Thanks PS: I know i have wrote 2bytes , I did it because the variable it's an INTEGER.
	Last edited by: sbartoc at: 5/2/2014 11:24 AM
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5/2/2014 11:51 AM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/17/2023 Posts: 1523 Rating: (518)	And it with 16#000F (the mask value). That will get you the least significant nibble. In your example the 1111. So in SCL it would be:- a := b AND 16#000F; In STL it would be:- L #a; AW W#16#000F; T #b; If you want to parse out other parts of the word, just use different mask values. The mask value will be:- 2^n + 2^n+1 + 2 ^n+2 etc were n is your starting bit. So in your example the mask value will be 2^0 + 2^1 + 2^2 + 2^3 = 1 + 2 + 4 + 8 = 15 (000F Hex). If n is not zero (i.e. your are not selecting from bit 0) then you might need to shift the resultant data to get it into the correct position in the result. For example your 'a' valus is 16#ABCD and you want to extract bits 8-11 (B is the word). Your mask value would be 2^8 + 2^9 + 2^10 + 2^11 = 3840 (0F00 Hex). b := a AND 16#0F00 = 16#0B00. Now if you wanted just the 'B' part of the word you would have to shift the result right by 16 places giveing the value 16#000B.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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5/2/2014 12:11 PM	Rate (0)
sbartoc Bronze Member Joined: 3/3/2014 Last visit: 3/20/2023 Posts: 221 Rating: (8)	Thank you for having responded quickly, I have a couple of question. First of all, what kind of variable is a? Byte? then how can i represent a in HEX? I expose shortly my "problem". I have a sum, that after Call INT_TO_STRING is like '320'. Now I want to divide all the information in 4 equal parts and make what you told me in the previous post. Then I have to represent the four part in HEX and finally use (I suppose) the FC95 fuction hexto ascii to have the ascii code. Is right my poinf of view in your opinion or there's a better way?
	Last edited by: sbartoc at: 5/2/2014 12:19 PM Last edited by: sbartoc at: 5/2/2014 12:18 PM
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5/2/2014 3:12 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/17/2023 Posts: 1523 Rating: (518)	'a' can be a byte or a word. What do you mean "represent it in HEX"? It will shown in hex by the S7 system programming environment / debug if it is a byte or word. Is it that you now want to conver the hex value to a string of ASCII characters? e.g. 16#0B00 -> '0', 'B', '0', '0'. Or are you trying to take a string (e.g. "ABCD") and spilt that up? If you are wanting to split up a string, you will need use the string slicing functions LEFT, RIGHT & MID. What is your starting point for the data and what do you want to get from this data. Please specify your requirements clearly to prevent misunderstanding.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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5/2/2014 3:18 PM	Rate (0)
sbartoc Bronze Member Joined: 3/3/2014 Last visit: 3/20/2023 Posts: 221 Rating: (8)	I have a number, 240 (decimal). I want to represent in base 16, that should be F0. Then I want to convert in String with INT_TO_STRING. thanks for the patience
	Last edited by: sbartoc at: 5/2/2014 3:22 PM
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5/2/2014 3:34 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 2/21/2023 Posts: 6794 Rating: (1340)	sbartoc I have a number, 240 (decimal). I want to represent in base 16, that should be F0. Then I want to convert in String with INT_TO_STRING. thanks for the patience It is not difficult to do scuh task with FC95(HTA) as dicussed in previous discussion.You have an address(INT) that contains adecimal value 240 ,No need to convert to WORD by INT_TO_WORD instruction,provide the address in IN parameter of FC95.Note "W#16#00F0" occupies 2 bytes while converted equivalent (as character) '0' , '0' ,'F' ,'0' occupies 4 bytes and you should consider that while providing OUT parameetr in metioned function.Just try it as it is really easy to perform. If you have problem using POINTERS , just use memory area in DBs that reduces the complexities. I hope these comments help you Hamid Hosseini
	Last edited by: hdhosseini at: 5/2/2014 3:43 PM Last edited by: hdhosseini at: 5/2/2014 3:35 PM Demo Channel on Youtube
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This contribution was helpful to 2 thankful Users smiffy sbartoc

5/2/2014 3:54 PM	Rate (0)
sbartoc Bronze Member Joined: 3/3/2014 Last visit: 3/20/2023 Posts: 221 Rating: (8)	it is very frustrating don't understand a simple like this, believe me. I did this code till now. Out: ARRAY[1..80] OF CHAR; test_int:=240; str:=FC95(IN:=test_int ,N:=4, OUT:=Out); Where I'm wrong?
	Last edited by: sbartoc at: 5/2/2014 4:09 PM
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5/2/2014 4:22 PM	Rate (2)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 2/21/2023 Posts: 6794 Rating: (1340)	sbartoc it is very frustrating don't understand a simple like this, believe me. I did this code till now. Out: ARRAY[1..80] OF CHAR; test_int:=240; str:=FC95(IN:=test_int ,N:=4, OUT:=Out); Where I'm wrong? To point out problems of shared codes: N should be 2 as you are working on INT and it should be in WORD fromat i.e W#16#02. IN and OUT shoud be pointers in form of 32 bits.As I mentioned it previously try to use addresses in DBs. If your application is to use it in an FB,Note that it is possible to assign an input of FB as Pointer. For more information, please read the online manual of STEP 7 as it is easy to access to information as it is case sensitive.It is also possible to search the forum or online support for more helpful tips.
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5/5/2014 8:47 AM	Rate (0)
sbartoc Bronze Member Joined: 3/3/2014 Last visit: 3/20/2023 Posts: 221 Rating: (8)	Sorry, I have wrote you in the other discussion. Big Big thanks also to @smiffy. Thanks guys, yu have been so patience with me Have both a nice day

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