instruction Execution Times

[BobO]

Those interrupts are just freaking amazing. I never thought the day would come that you would be able to effect control within 50 microseconds on a PLC costing under $400.  Thanks for having the latency and execution time values. Big Help. Good job.

Thank you, sir. Glad you find them useful.

[ATU]

I couldn't find anything in the help to verify this.
I am using a recurrent timed interrupt at 10ms.  Is  that timing done in hardware outside of the PLC OS?  In other words, is there any  accumulative latency for the call or is the periodic execution of the ISR going to be exactly  a 10ms tick + whatever the  call's Latency was at that time?

[BobO]

It is timed by dedicated logic in the FPGA and there should be no cumulative error. Not so say that there isn't though...could be bug. The oscillator that drives all of this isn't super-duper accurate though (leading to fairly high clock drift) so that could also taint your view.

[ATU]

I was seeing a small shift on the scope and tracked it down to other issues.
However, It got me thinking about the accuracy of the interrupt over longer periods of time (such as duration's lasting days and weeks) and wanted to make sure I would not be getting any major accumulation of error from the timer itself. Might be useful to add that information in the help for the timed interrupt.