ControlLogix 5000 Word Shift Register

Guest · Jul 21, 2005

Hello All,

Is there an instruction in ControlLogix to shift a word like a Bit Shift shifts bits. We are looking for a number to be equal to a bin number to place the product in. I have used multiple MOV instructions in SLC. It would be nice to reduce them down to one instruction.

Thanks

PhilipW · Jul 22, 2005

I think you are either asking for a simple COP (Copy) instruction, or a FIFO/LIFO. Let us know if these are not what you have in mind.

jstolaruk · Jul 22, 2005

See BSL (Bit Shift Left) and BSR (Bit Shift Right). Featured in RSLogix 5000 v13.03.00

Guest · Jul 23, 2005

As product is transfered through the system we what to move one word with it. Word 1 moves to 2, 2 to 3, 3 to 4 and so on. With the MOV instruction you would have and so on 3 to 4, 2 to 3, 1 to 2. We would like to clean to logix up by not having a bunch of MOV of COP (lenght of 1) instructions. Is there 1 instruction in ControlLogix to do this? A word shift instruction?

Thanks

PhilipW · Jul 23, 2005

Will this old trick do it for you?

COP
Source = Array[1]
Dest = Array[0]
LEN = <Length of Array - 1>

Basically the COP sequentially moves Word 1 onto Word 0, then Word 2 onto Word 1, etc. This sounds very close to what you want.

Guest · Jul 23, 2005

PhilipW we need more information.

For example we have 20 words to shift, Array[0] to Array[19]. We want to transfer from Array[0] to Array[1], Array[1] to Array[2], Array[2] to Array[3] . Can this be done with 1 COP Instruction?

Guest · Jul 23, 2005

PhilipW

You forgot to tell me to load Array[19]. Works great for shifting words down, Array[19] to Array[18], Array[18] to Array[17], Array[17] to Array[16]. To make adjustment to array and system length would cause a lot of editing. We want to shift the words up.

PhilipW · Jul 23, 2005

Try loading the instruction as shown and see how it works.
Put the most recent value in Array[19] and the single COP as described will move all the words UP.

Doug-P · Jul 23, 2005

Copy Array_A[0] to Array_B[0] with length = 19

Copy Array_B[0] to Array_A[1] with length = 19

All values in Array_A have now been shifted up by one word and Array_A[0] is ready to accept new input data.

Contr_Conn · Jul 23, 2005

To shift words up, You will need 2 COP instructions to prevent filling the array with Array[0] value.

COP
Source = Array[0]
Dest = TEMPArray[0]
LEN = <Length of Array - 1>

COP
Source = TEMPArray[0]
Dest = Array[1]
LEN = <Length of Array - 1>

PhilipW · Jul 23, 2005

Actually I suggest you actually try the very simple one COP method outlined. It works by shifting all the members of the array UP. The newest member is put at the end of the array and the oldest is overwritten at Array[0].

It works by virtue of the sequence the CLX uses to implement the COP.

Contr_Conn · Jul 23, 2005

PhilipW:
COP instruction is not smart to do COPY UP from the top, it will always do copy from the bottom, overriding all values.
COPY DOWN works fine.

I tested this with CLX ver 13:

BEFORE

ARRAY[0] = 0
ARRAY[1] = 1
ARRAY[2] = 2
ARRAY[3] = 3

AFTER COP ARRAY[0] ARRAY[1] 3 (copy up)

ARRAY[0] = 0
ARRAY[1] = 0
ARRAY[2] = 0
ARRAY[3] = 0 (This is not result you want)

AFTER COP ARRAY[1] ARRAY[0] 3 (copy down)

ARRAY[0] = 1
ARRAY[1] = 2
ARRAY[2] = 3
ARRAY[3] = 3

To do copy UP you will need 2 COPs like I described earlier:

AFTER
COP ARRAY[0] TEMP[0] 3
COP TEMP[0] ARRAY[1] 3 (copy up)

ARRAY[0] = 0
ARRAY[1] = 0
ARRAY[2] = 1
ARRAY[3] = 2

Gerry · Jul 23, 2005

You guys need to agree on which way is up.

Contr_Conn · Jul 23, 2005

I usually count UP: 1,2,3...

Going UP in my examples ARRAY[0] data going to ARRAY[1]. Is this UP? 0->1?

PhilipW · Jul 23, 2005

I guess UP is all relative. I meant 1 > 0, which is the same way it looks when monitoring the array in RSLogix.

Copy Down as you have described Contr_Conn is the simplest way to create a Word Shift Register with ONE instruction and one array...as originally requested. So what if the data goes the opposite way to what might be considered UP or DOWN, it works.

ControlLogix 5000 Word Shift Register

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