Just going to try and go through each part of your post here…
I assume that the IO processor is free running and continuously scanning the I/O modules, gathering the data, doing some conditioning if so configured and placing this data in the OptoMMP memory map.
Yes that’s correct. The IO processor is not part of the control chart processor. It just takes care of the I/O for the most part.
I also assume that the controller, running charts, is accessing this block of memory at a controlled interval. For example if I set up a chart with a timer and schedule it to “READ” into a “table” so that I can then process this data.
How often does the IO controller scan the modules and update the data in the memory map?
As your chart requires. So if your chart only has a 10msec delay in it, then your chart would scan the modules and update the data every 10 milliseconds.
(Which is where we get into your next bit about data freshness).
There is mention in the specs of freshness of data. What does this mean?
This is the Analog to Digital converter ‘speed’ (not exactly, but good enough). In other words, you can poll the module every 10 msec, but you will only get fresh data (new data) every 23 msec.
The number of modules you have is irreverent. Each module has its own A to D converter and that takes 23 msec to do the electrical to digital conversion.
No. Yes. Yes.
There is no synch between the modules and the I/O processor. The modules are free running converting, so you always have the fresh data sitting there every 23 msec.
Even if you don’t read it, it will be over written by the module 23 msec latter, so when you do read it from your chart, you always get the latest value.
Your chart command kicks off the scan of that value.
Yes, the I/O processor is always getting the latest value from all the modules.
Is there a suggested way to measure the scan time of the IO processor?
Don’t bet the house on it, but PAC Manager has the data closest to what you ask.
Note that your value will be different to mine here, it will depend on the amount and type of modules you have in the rack.
Also high density have their own scan rate and will not show up here.
Hope this helps.