Byte Swap in PLC-5

I'm writing a PLC-5 program that receives a barcode string over DH+ that ends up in an Integer register in the controller.

The challenge is that the data is "byte swapped", so that when I move it into a STRING data type the individual bytes in each word are backwards from human readable.

I have: ABCRDO1E
I want: BARCODE1

Does anyone have a code snippet or subroutine to share that will swap the bytes in an array of PLC-5 integers? In the SLC-500 and ControlLogix I have the convenient SWP instruction, but in the PLC-5 I have to do it by hand.

I havent got what you want Ken, but if you want to swap say N7:0.0-N7:0.7 with N7:0.8-N7:0.15 (i speak decimal better than octal) is it possible to write a routine using indexed addressing that would increment on scan to move the bits into another register in the order you need them. Hope this makes sense. Alan Case

This is funny


The AND before the MUL is required to avoid overflowing 32767. This assumes you are using ascii characters only and therefore all characters are in the range of 0-127.

The AND after the DIV will not be required if you are only using ascii data because the integer will always be positive.

I cant seem to attach 2 jpegs to the same post.

This example will give you 10 integers of converted data starting at N7:20 with the source data being 10 consecutive integers starting at n7:0

and this:

I ended up doing it exactly the way 93LT1 illustrated.

Peter, I was thinking about using DIV and MUL to shift bytes around, but I didn't have it clear in my head (up all night working on this!). I think those instructions might be faster than making the PLC-5 move all those bits around. It probably won't be discernible in scan time, but I'll see about doing it both ways to compare.

Thanks, guys !