Lpc2000

At 12:48 PM 2/14/04 -0500, you wrote:
>     Most of our 3.3V designs use 10K pullups, and it's never been an
>issue.  That being said, my experiences do not yet include the LPC2100.
>Reading the port specs, they don't seem out of line, so I'd select a 10K
>in most cases (I'd like to find out who designed the port architecture
>on the LPC2100, and viciously beat them about the head and shoulders
>with a golf club.  You'd think Philips would know SOMETHING about port
>design, given their 8051 experience.  No selectable internal pullups?
>What WERE they thinking?) .

I don't know, I've found internal pullups to cause almost as much trouble 
as they prevent. I'm will to spend a few cents on external resistors.  Of 
course if you are really tight for space....  At least they didn't 
implement QBDs.  It may be a matter of keeping the I/O cell small enough to 
include other features.  That's a tradeoff I'll certainly take.


>     In the olden days of slower TTL logic and lower noise immunities,
>4.7K pullups on 5V logic was pretty much the norm.  These days, stiff
>pullups for "normal" signals (parts with good current sink capability,
>better immunity to noise, etc) aren't really necessary.

I think you may be dating me. :)  The bigger reason I still prefer 4K7 
pullups is that the HW I've played around with in the recent past is 
throwing around 100's of Amps relatively close to the micro.  I'll take all 
the noise immunity I can get :)

Nonetheless 10K pullups certainly should not cause a problem.



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