I saw a mention of PICs with < > and = functions. I'm not familiar
with the particular one, 766 was it ?, but I plan to use PICs other
than the F84 next year. I've a specific app that I want to know
whether there's a PIC to suit.

I'm using a sampling chip that employs CVSD ADC, Continuously
Variable Slope Delta-modulation. What it does is sample the signal
and compare it to the last sample. If higher it produces a "1" data
bit, if lower a "0" data bit. When the signal is flat-line it alternates
ie puts out a 55 or AA byte. This would appear to be an efficient
way of sampling, as only the direction of the wave is noted, not its
absolute value, it works very well anyway. Sampling rate is >60kHz
and 10-bit resolution.

The question I have is ; is there a PIC that has ADC and comparison
functions that will emulate this sampling chip at speed ? From the
limited reads I've had of ADC PICs, it looks as though 20us is about
the max. The primary reason for asking is that the sampler is now out
of production and I'm relying on stocks to see me through.

Alternatively, can anyone suggest a way of using discretes to do the
same thing ? It has to be done at least > 50kHz to maintain signal
integrity. I want to to rationalise the whole circuit using 1 or 2 PICs,
rather than the sampler/PIC combination there now. If two PICs are
needed that's OK, perhaps one sampling, the other supervising. An
external ADC for a PIC to read is acceptable. Speed and resolution
are important, I don't especially care how it's done.

Jinx