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400 Bit shift register

Created by: AutoGen_679171 at: 1/12/2015 9:53 AM (7 Replies)

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1/12/2015 9:53 AM	Rate (0)
AutoGen_679171 Posts: 3 Rating: (0)	I need to make a shift register which is approximatly 400 bits long in an s7-1200 PLC. The input bit (left hand) of the shift register needs to load with either 0 or 1 according to the state of a digital input. Another digital input causes the entire register to shift 1 bit to the right. Operation speed is quite slow, bit shift occuring at about 1Hz. I need to be able to look at the value of 8 different bits at specific points along the register. If anyone can help me out, i'm willing to pay, but i urgently nedd some help on this. thanks,
AutoGen_679171 Posts: 3 Rating: (0)
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1/12/2015 2:18 PM	Rate (0)
eisenpferdreiter Posts: 1058 Rating: (93)	AutoGen_679171 I need to make a shift register which is approximatly 400 bits long in an s7-1200 PLC. The input bit (left hand) of the shift register needs to load with either 0 or 1 according to the state of a digital input. Another digital input causes the entire register to shift 1 bit to the right. Operation speed is quite slow, bit shift occuring at about 1Hz. I need to be able to look at the value of 8 different bits at specific points along the register. If anyone can help me out, i'm willing to pay, but i urgently nedd some help on this. Hello AutoGen_679171, I would suggest following solution: For this solution your shift register needs to have a multiple of 8 bits. Createa DB with an array of 400 bits (0...399) and another array with 401 bits (0...400). The 400 bit array will be your shift register, the 401 bit array is an auxiliary register. I will describe here the program in pseudo code, so you can implement in any language. For right shift: Your trigger bit (for shifting) will enable (EN input) following operations: Use SFC20 BLKMOV to move bits of your shift register to auxiliary register. Input SRCBLK is a bit pointer that points at bit 0 of your shift register. Output DSTBLK is a bit pointer that points at bit0 of auxiliary register. Write input bit (left hand) to auxiliary register bit 400 (last bit of array). Use SFC20 BLKMOV to move bits of your auxiliary register to shift register. Input SRCBLK is a bit pointer that points at bit1 of your auxiliary register. Output DSTBLK is a bit pointer that points at bit 0 your shift register. For left shift: Your trigger bit (for shifting) will enable (EN input) following operations: Use SFC20 BLKMOV to move bits of your shift register to auxiliary register. Input SRCBLK is a bit pointer thatpoints at bit 0 of your shift register. Output DSTBLK is a bit pointer that points at bit 1 of auxiliary register. Write input bit (left hand) to auxiliary register bit 0. Use SFC20 BLKMOV to move bits of your auxiliary register to shift register. Input SRCBLK is a bit pointer that points at bit 0 of your auxiliary register. Output DSTBLK is a bit pointer that points at bit 0 your shift register. regards
eisenpferdreiter Posts: 1058 Rating: (93)	Last edited by: eisenpferdreiter at: 1/12/2015 2:30 PM
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7/27/2015 11:40 AM	Rate (0)
Tim_M Posts: 2 Rating: (1)	What about this one: very simple, S7-1200 Create a DB and ARRAY of your needed number. Input switches ON the array 0. Next network: (Ladder). MOVE_BLK: EN - Positive or negative clock IN - array 0 COUNT - your needed number (arrays on DB) OUT - array 1 Next network: your array number(X) and output. * I would retain the values on the DB Regards
Tim_M Posts: 2 Rating: (1)
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10/8/2018 4:34 PM	Rate (0)
NiM_0021 Posts: 102 Rating: (25)	Hi AutoGen_679171 how about using a SCL-network? Create the following FC: INs: STATE_OF_1st_BIT := BOOL LOAD := BOOL SHIFT := BOOL END_IN IN_OUTs: BIT_REGISTER := ARRAY[0..399] of BOOL END_IN_OUT TEMPs: i := int END_TEMP CODE: IF #LOAD THEN #BIT_REGISTER[0] := #STATE_OF_1st_BIT; END_IF; IF #SHIFT THEN FOR #i:=398 to 0 BY -1 DO #BIT_REGISTER[#i+1] := #BIT_REGISTER[#i]; END_FOR; END_IF; END_CODE if you apply a positive flank to #LOAD, the value of #STATE_OF_1st_BIT will get written to the first digit of your register. If you apply a positive flank to #SHIFT, the #BIT_REGISTER will shift each of the values one place higher. ALTERNATIVE: INs: STATE_OF_1st_BIT := BOOL LOAD := BOOL END_IN IN_OUTs: BIT_REGISTER := ARRAY[0..399] of BOOL END_IN_OUT TEMPs: i := int END_TEMP CODE: IF #LOAD THEN FOR #i:=398 to 0 BY -1 DO #BIT_REGISTER[#i+1] := #BIT_REGISTER[#i]; END_FOR; #BIT_REGISTER[0] := #STATE_OF_1st_BIT; END_IF; END_CODE if you apply a positive flank to #LOAD, the #BIT_REGISTER will shift each of the values one place higher, then the value of #STATE_OF_1st_BIT will get written to the first digit of your register. NOTE: USE FLANKS AS SIGNALS FOR #LOAD AND #SHIFT This code is not tested, please do so before implementing it to your final project.
NiM_0021 Posts: 102 Rating: (25)
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1/13/2022 9:51 AM	Rate (0)
Eng. Ken Regular Member Joined: 8/9/2018 Last visit: 1/22/2023 Posts: 7 Rating: (0)	Not working. tried it in ladder but no results

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1/13/2022 5:24 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/14/2025 Posts: 15533 Rating: (2465)	You can take on the challenge of using this computer programming algorithm and converting to PLC SCL: https://stackoverflow.com/questions/59440813 Eng. Ken Not working. tried it in ladder but no results
	science guy
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1/13/2022 9:07 PM	Rate (0)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 1/14/2025 Posts: 4846 Rating: (741)	Eng. Ken Not working. tried it in ladder but no results Then show your efforts.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
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1/13/2022 10:16 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/14/2025 Posts: 15533 Rating: (2465)	Oh wait, you tried to simulate a for loop in LAD? Oh my, I can see why it did not work. That's a very tricky thing to do in LAD. I did it once as an exercise just to prove it could be done. It took a very LONG time to get working correctly, but eventually after much effort, the for loop simulation in LAD worked. I then wrote it in SCL in minutes (perhaps even seconds). You can click the built in FOR block from the favorites bar and you're 90% there in SCL, perhaps even 95%. jacek d Eng. Ken Not working. tried it in ladder but no results Then show your efforts.
	science guy
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