"a shift regiser, it is a group of registers set up in a linear fashion which have their inputs and outputs connected together in such a way that the data is shifted down the line when the circuit is activated...i got this from
http://en.wikipedia.org/wiki/Shift_register the serial-in. serial-out would be my application, but i have no ideal how to do this in controllogixs processor.
I don't know 'controllogixs' either, in fact I only know Modicon Ladder Logic, but every PLC has a way to do what you want.
It looks like you want to collect data regularily (based on a timer timing out perhaps?)
You want to store a certain number of these hunks of data. (how many?)
You want to shift the data through the registers so that the first hunk of data in, is the first to fall out the botttom, never to be seen again (FIFO)
You may want this series of contiguous(sp?) hunks of data to provide a trend? or perhaps an average?
Modicon has the R->T instruction to copy the value in a register into a specific register located in a table (stack)
There is also the FIN instruction which copies data into the first register in a queue(table,stack) of holding registers. It automatically bumps the previous data down until the queue is full.
This is used with the FOUT instruction to create FIFO logic.
I bet you are still confused. Don't worry! Someone here knows your PLC.
Brian.