Lpc2000

Yes, I did mean VIH.  I forgot to preview before I posted.  I'm
interfacing to a Futaba LCD Emulator.  Some of the inputs are spec'ed
at 0.8*Vcc and others are at 0.7*Vcc Min.  I checked with an App
Eng at Futaba USA and he indicated that 3.3 volt logic will not drive
the device. Since I only have 3-signals to this device (serial
interface), its probably safe to use a AHCT125 device.  The only
problem is that the data I/O line is bi-directional therefore an
additional GPIO is required for this input.

   Barry

Peter Jakacki <peterjak@t...> wrote:
> Vol ??? You do mean Vih, don't you? In my experience I've never had
a 
> problem with driving 5V logic from 3.3V as the minimum Vih in is 
> specified for full-speed digital switching. The 3.3V definitely
drives 
> the 5V logic as a logic high but it may not work to "parametric" 
> specification at 100Mhz etc. For all your normal I/O work it is
never a 
> problem and I don't let myself lose sleep over it.
> 
> You can though for peace of mind and sleep use pull-up resistors to
+5V 
> on the output lines and simply simulate open-drain drivers by
writing 
> the IODIR. It doesn't matter if you initially drive them to 3.3V
and 
> then float by switching to inputs with the pull-up. IMO, skip the 
> buffers, they are always overkill.
> 
> my2cents
> *Peter*
> 
> p.s. Hey Rob! I dug out the TI yellow bible and mine is dated 1988.
I 
> also remember my first logic data book, it was a big red Fairchild 
> Semiconductor TTL data book from the early '70s. Back then you
needed 
> PSUs that could supply amps, none of this itsy-bitsy pencell
battery 
> stuff! Plus you had to worry about fanout (both the blower type and 
> driving type).
> 
> 
> javida13 wrote:
> 
> >I have a 5 volt logical display that I'm driving.  The Vol for
this 
> >part is 3.5 volts (.7*Vcc).  I have 3-signals that must be driven
to 
> >this logic level.  Is there a LS type of device that can be used as
the 
> >level translator, where is can be powered by 5 volts and its input 
> >level can be driven by 3.3 volt logic? 
> >