"You Are Here" Logic - to re-start where you left off

Hey OptoPros,

I had a question from a customer who wanted to be able to make changes to their strategy w/out too much downtime. E.g., they couldn’t spend long downloading and re-starting their whole process. Hoping you’ll share how you’ve approached this type of problem.

A couple thoughts:

  1. Use the “background download” feature. While this splits your SNAP-PAC-R or -S controller’s memory in half, it can let you change strategies faster without having to wait as your new strategy downloads. (Because you have the current strategy in one half of your memory, and the one you’re downloading in the other half.)

  2. Add some “you are here” logic to keep track of where you process is so you can pick up where you left off.
    For example, in our Cookies example strategy, there are 5 charts total, so you’d need a persistent variable for each of the 5 charts to store the current location (like the block ID) of where the process is in each chart.

    Ends up looking a little like an exoskeleton for your chart – the orange blocks on the right, in the Alarms chart of this example, keep track of where you currently are, then (when starting from Block 0), send you back there upon a re-run of this chart.

Thoughts? Better ideas? Do share!


This is basically what I would do as well. Most of my processes, whether it’s controlled by an Opto22 controller or PC or any other type of controller, include state variables that tell the program where it is in the process. This state variable is typically persistent so when the device reboots it knows where to go.