Lpc2000

What's the best way to drive 5v logic with the LPCxxxx GPIO?  Pull up 
resistors?  I seem to remember reading somewhere about using pull-up 
resistors, but I don't see any information in the LPC2106 reference 
manual on how to put the outputs in open-drain mode.  I'd appreciate 
any advice on this.

Thanks.

Also, thanks to those who replied to my previous questions.  

- Chris Graham

--- In lpc2000@yahoogroups.com, "Chris" <chris_e_gr@y...> wrote:
> What's the best way to drive 5v logic with the LPCxxxx GPIO?  Pull 
up 
> resistors?  I seem to remember reading somewhere about using pull-
up 
> resistors, but I don't see any information in the LPC2106 reference 
> manual on how to put the outputs in open-drain mode.  I'd 
appreciate 

You should be OK just driving the 5V logic from the outputs, TTL has 
a 2.4V threshold.

Leon

At 08:42 PM 5/25/04 +0000, you wrote:
>--- In lpc2000@yahoogroups.com, "Chris" <chris_e_gr@y...> wrote:
> > What's the best way to drive 5v logic with the LPCxxxx GPIO?  Pull
>up
> > resistors?  I seem to remember reading somewhere about using pull-
>up
> > resistors, but I don't see any information in the LPC2106 reference
> > manual on how to put the outputs in open-drain mode.  I'd
>appreciate
>
>You should be OK just driving the 5V logic from the outputs, TTL has
>a 2.4V threshold.

Check the input minimum guaranteed high voltage threshold.  TI specs a 
74HCT08 at 2V and a 74HC08 at 3.15V.  The ouput voltage of the 2194 (It's 
the datasheet I have to hand) is specced at .4V below the 3.3V power supply 
for a 4mA draw. As Leon says if it's a TTL input it will probably work, but 
check.  True CMOS inputs may require more thought, a 74HCT buffer would 
probably be sufficient, and easy.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III