Budke

Thank you for the input.  A couple mentioned the IIM instruction.  I've never used it before, but it sounds like it will work.  I'll give it a shot.  The size of the program is 385 KB.  It was originally written with all of the program being scanned each time.  Trimming it down into event-driven sequences at this point would be difficult.

I have a 1746 HSCE2 card installed and working in a SLC 5/05 chassis.  However, the SLC is running at a scan rate of 33ms, and that is hindering the accuracy of my machine.  Here's what I'm doing: each time a prox is seen by a digital I/O card, the PLC takes the current encoder counts from the 1746 HSCE2 card, subtracts the previous encoder counts (last time the prox was seen), and stores the difference in a register.  Basically, I'm just determining how many encoder pulses I have between each time the prox is seen.  The problem is that with a 33ms scan rate of the PLC program and with the speed of the machine, the methodology isn't accurate enough.  Is there a way to get more flexibility out of the 1746 HSCE2 card and have it handle more of the task so that I'm not hindered by the PLC scan rate?  For instance, can I wire the prox into the 1746 HSCE2 card to the encoder 2 spot somehow, have the cards processor determine how many encoder counts were seen from encoder 1 between pulses of the prox, and then put that in the encoder 2 count value (the output from the card and the input to the PLC).