How random is "RANDOM"?

[BrianT]

Simply reading TMR0 or TMR1 is NO guarantee of a random seed.

In some systems where the code runs for days and takes innumerable branches and folds it might be pretty good but in other systems the code trajectory is the same every time the code is run. In that case TMR0 and TMR1 will always yield the same values.

You MUST introduce something truly indeterminate, such as a noise source or an unpredictable delay such as a human operator where response times will vary every time the operator pushes the button.

BrianT

[skimask]

Simply reading TMR0 or TMR1 is NO guarantee of a random seed.

Agreed 100%...but...if running on an internal oscillator, it could vary with temperature, perhaps far enough to mess with the seed enough. After all, theoretically, it only takes a single bit difference to change the order of things completely...theoretically that is
And exact temperature, therefore precise oscillator speed, is truly indeterminate, if, as you say, you have an external event trigger that is nonperiodic (aperiodic? anti-periodic? periodic-less?)