Lpc2000

At 07:47 AM 10/24/04 +0000, you wrote:
>I am designing a board based on LPC2124 and I want to reset the
>device when the core voltage (1.8v) is not good. I have a voltage
>supervisor of 1.8v which makes the reset (0v) but after the reset it
>supplies 1.8v to the reset pin. Is this a legal voltage for the reset
>pin? The manual says that this pin is Schmitt trigger but also says
>that is TTL compatible. So, during reset I will have no problems but
>after reset? Is 1.8v capable to bring LPC2124 out of reset condition?

You probably want an open drain reset device rather than a push-pull.  A 
simple pullup will then provide the voltage to take the processor out of 
reset.  As an added bonus you can also parallel reset sources.

Another item to watch for, make sure the reset device holds the reset low 
for the full time period required.  Most do, but a simple comparator is 
likely to be too fast.

BTW the data sheet states the minimum level high input for the reset pin is 
2.0V.

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