> > 2 You think strobing a 7-seg is time critical?
> 
> Indeed. You think it is not?

Indeed. There are somne timing-related aspects that might matter, but it
does not matter whether the refreshing is done at 200 Hz or 10 kHz. 

> One thing that I discovered when working with those 4-character
> alphanumeric LED displays from HP (used on a high-end telecom product)
> was that the slightest variation in refresh timing caused very visible
> random brightness variations.

Which type of variation? I find it hard to believe that for instance a
small change in the frequency is visible att all.

> All who saw it agreed that it was not
> acceptable. This was on an 8051-clone, so I ended up doing a 
> "precision
> reload" of the timer so that the only variation in display timing was
> the 1 or 2 machine cycles of jitter in the interrupt latency (and zero
> cumulative error).

The fact that that solved the probleb does not prove (at least not to
me) that it was necesarry.

Wouter van Ooijen

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