Lpc2000

--- In lpc2000@yahoogroups.com, "Leon Heller" <leon.heller@b...> wrote:
>

> 
> I think that is probably the case, contrary to what I said earlier.
Ground 
> bounce due to poor construction techniques may be one reason why
some people 
> have problems getting it to work reliably.
> 
> Leon
>

There is also another problem that can occur, and is VERY difficult to
detect sometimes. Without a Schmidt trigger input, if the input
voltage to a logic device changes too slowly through the transition
region, the output will be metastable or oscillate. It happened to me
one time with a circuit that had a clock speed of just a few hundred
kilohertz, and the logic would not work!  In this case the clock input
was from an analog source that had a relatively slow transition time,
so the clock inside my logic had bursts of 50MHz oscillation on each
clock transition. When you have a scope set to look at a low frequency
signal of a few hundred kilohertz it was really hard to notice the
much higher 50MHz signal in the transistions, but the logic knew!!!!

So you need to be very careful with slew limiting the logic signals
with logic not designed to work with slow transitions.

--Dave