That´s a big problem. To go sub-100ns you must make frequency > 10Mhz,
and most of these chips only run at >10MHz using internal PLLs (you
can´t directly clock them with more than about 20MHz.. or at least the
datasheet says so).
A FPGA has no such problems (or at least they are very atenuated because
you can directly clock them at 200Mhz easily).
But.. have anyone looked at the CTMU as an interval counter?
Daniel
Em 23/01/2014 19:00, Tom Van Baak escreveu:
Has anyone else looked at the Parallax Propeller processor for timing
functions?
Hi Brian,
Oh yes. Really nice chip. But for precise timing applications I had huge
problems with phase and temperature stability of its internal PLL. I tried half
a dozen different boards purchased over several years. Tech support was not
interested in someone who worried about nanoseconds.
The architecture is really interesting, but it is such an odd chip, with almost
zero market visibility these days, that I set aside the goal of using it as the
basis of a general purpose 8-channel 6 ns precision counter. You can find
various timer and counter examples at obex.parallax.com. If you make progress
on the project, please let me know, ok?
By contrast, the PIC chips I use are fully synchronous so when you use 10 MHz
atomic references the clock/output jitter and phase stability is almost below
what I can measure here. Maybe under 2 ps. So that's why I use PIC's as the
basis of all my picDIV and picPET projects. But I'm open to using something
different in the future.
/tvb
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