Word shift Logix5000

I am trying to track product as it advances through a rotary indexing table. Been playing about for the past hour but not making much progress.

The table has 4 nests. Nest 1 is load and 4 unload. I have a DINT array "Nest(0)...Nest(3)". The id is a 4 digit integer. I have a rung where the 1st ID is MOVed to Nest(0) from InitID (initial ID) which is entered on the HMI.

I tried to MOV the data but ended up having the 1 ID entering all nests simultaneously. I tried to resolve this with ONS and OSR but didn't have any joy.

I am now trying to use the COP function. I read you have to do it backwards. So once my initial ID is in nest one, I trigger a COP with the same bit that indexes the table. The COP data is:
Source: Nest(3)
Destination: Nest(2)
Length: 4

...this isn't working either?

try this:

The COP data is:
Source: Nest(1)
Destination: Nest(0)
Length: 4

if the "going backwards" idea gives you a problem - look up "ratchet" on the forum ...

that method takes up twice as much memory (who cares for just 4 locations in your example?) but the data can be made to "march forwards" - which makes it easier for us humans to visualize what's going on in the system ...

Thanks Ron, I had a go at that. I entered 1001 into the HMI and triggered the bit which MOVed this to Nest(0)

I then clicked the button to index the table, and the DINT array filled all elements with the number "-2,147,483,637"

I also tried the ratchet method following the example here: http://www.plctalk.net/qanda/showpost.php?p=360484&postcount=3

When I indexed the table, all 4 nests got the value of the initial ID

the_msp said:

When I indexed the table, all 4 nests got the value of the initial ID

Click to expand...

The COP instruction and the technique illustrated at the link must also be 'one-shotted' if you don't want your data to quickly transit the file. MOV, COP and suchlike instructions execute whenever rung conditions are true.

Instructions such as: FAL, FSC, and counter instructions (all of which have associated status bits) execute only once for each false-to-true rung transition. The condition must go false and true again to get another operation.

If you want to keep your data in order then one shot a series of Copy instructions 2 to 3 then 1 to 2 then 0 to 1 then Int_ID to 0. This way you move your data before you over write you data. I said series or you can branch. This Logic could be solved in a series left to right or with a branch Top to Bottom.

try the RIPPLE method like this ... it's working just fine (at least the way that I THINK that you want it to) on my system ...

.

I got it working using the ratchet method after adding an ONS as Doug suggested, thanks all

or the RATCHET method to move the data "forward" through the nests ...

.

Yes Ron I'm using that method, only difference my COP's and MOV are in series.

series is fine for RSLogix5000 - I usually put them in branches so that other platforms can run the same code ...

glad that you got it working ...

I'd strongly suggest just using the FFL/FFU instructions and being done with it.

Shift in data with a one shot each index using a FFL, and then when the .DN bit is set, you shift out data using the same trigger.
I usually use FFL/FFU in the same rung, triggered by a my single shift one shot:

ONS WhatEverBit BST FFL MyFIFO (parameters) NXB XIC MyFIFO.DN FFU MyFIFO (parameters) BND.

Hi ron,

thanks great help