R
Ray Andraka
- Jan 1, 1970
- 0
Jerry said:I wasn't thinking of the memory chips themselves, with charges on
capacitors standing in for ones and zeros, but rather the analog nature
of the interconnections, with their transmission delays, characteristic
impedances, and matched terminations. A flip-flop' set-up and hold times
arise from the underlying analog nature of its components. Even the
pulse width of the one-shot is quantized in trinary a way: long enough,
OK, and too short. Otherwise, they wouldn't be useful. (The memory
chip's charges are similarly quantized: in the zero range, trouble, and
in the one range.) I don't see the distinction between a digital and an
analog circuit element as fundamentally more meaningful than the
distinction between a digital and an analog wire.
Jerry
Yes, I agree that board designers need to take into account the analog
nature of the signal transmission, and I don't think any current media
for digital logic is wholly digital. That said, I guess I am looking at
it from an algorithmic point of view while you are looking at it from a
physical point of view. To me, digital basically means that your
circuit is using numeric methods rather than physical properties to
obtain the desired result.
Granted, you will have to take into account analog effects in doing a
complete digital implementation, but not for the digital algorithm
itself to work. The distinction is that for a digital circuit any
analog behavior is not germane to the algorithm, rather it exists (often
as a hinderance) as an artifact of the implementation. Contrast that
with an analog circuit where those device physical properties are a
necessary ingredient to a functioning design because you are exploiting
those properties to perform the signal processing.