8 Sep
2013
8 Sep
'13
10:47 a.m.
On 09/08/2013 10:15 AM, Chris Elmquist wrote:
Use a decent stability crystal or oscillator (as opposed to some on die
RC osc) to clock your micro and you should have it.
I'm with Tony on this one, however. There's a "mystery" aspect to using
an MCU for this sort of thing (i.e., code, programming). Index can be
isolated from sector pulses with a simple one-shot (as is done on old 8"
drives with separate sector and index lines). The rest is a simple PLL
setup with a divider. Robust, contemporaneous with no mystery at all.
It could just as well have been designed and implemented in 1972 as today.
Note that no crystal is necessary for a PLL, as the sector pulses
themselves serve as the reference. I suspect that the "capture ratio"
would be quite large also and quite tolerant of long term speed variations.
If this were a modern device, then I'd probably go with an MCU.
FWIW,
Chuck