[sdiy] Help, I'm Desperate! (Charge Injection with DG408)

[mskala at ansuz.sooke.bc.ca]

On Tue, 4 Dec 2018, Steve Lenham wrote:
> The ideal - though not always possible - way to eliminate these intermediate
> states is to make the system synchronous. You feed the asynchronous address
> lines to the inputs of a D-type latch, then clock the latch at a point where

Another thing often done to reduce glitches in this sort of situation is
to use a Gray code.  Instead of using the digital words in the sequence
000, 001, 010, 011, 100, 101, 110, 111, where all of them can change
between successive values, one might use them in the sequence 000, 001,
011, 010, 110, 111, 101, 100.  That way, only one bit changes between
successive words.  This is done for things like absolute position encoders
where you have a slow mechanical system driving digital logic and you
can't depend on both bits changing at the same time when two change.

I don't really understand how the digital logic is being used in David's
design and I fear that trying to retrofit Gray coding onto what he's
currently got might require so much change to the way the comparators are
being used, as to be impractical.  But it *is* a useful way to reduce
glitches when it's applicable.

-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before tribes.
http://ansuz.sooke.bc.ca/