9 Sep
2013
9 Sep
'13
1:43 p.m.
On Mon, Sep 9, 2013 at 12:49 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I don't know quite what your PIC firmware does,
but I think some kind of
digital phase-locked loop could be built from TTL on one reasonable-sized
board. So it shouldn't be too hard...
A DPLL seems like overkill, when a one-shot for index recovery, an analog
PLL (e.g. 4066 or 74HC[T]4066) and a counter should be more than adequate
to do the job, and would make the circuit much simpler to design and debug.
If you want selectable sector count, a programmable down counter (e.g.
CD4059, 74HC[T}4059, or MC14569B) could be used.
Personally I'd be fine with using a PIC, since it's apparently already
designed and working. Presumably the PIC circuit can be removed, so it's
not permanently contaminating the system with non-period components.