Lpc2000

On Wed, 20 Oct 2004 15:25:15 -0000, tsvetanusunov wrote:

> I'm not sure it is a bad idea.  The 74LCX244 connects to the ARM and
> gets its power (~3.3v) from the target board. The 74AC244 connects 
to the PC and gets its 5v from there.  

Bill, 
you don't follow Johns post - he is powering the target with 3V and 
the problem comes from LCX-to-AC direction as AC have threshold 3V 
for "1" high level and this is on the edge when LCX is powered with 
3.1V only

>The problem might be that the signal(s)
> FROM the 74LCX244 TO the 74AC244 are not above the 74AC244's input 
threshold
> level.  Changing the 74AC244 to a 74ACT244 would lower the input 
threshold
> requirement for the signal(s) coming from the 74LCX244 while still 
maintaining
> compatablility with the PC signals.

of course this is OK if *all* LPTs provide >4.5V which ACT will need 
as this part is powered from LPT

Best regards
Tsvetan
=========================================================================
It was my understanding that the 74AC244 got its power indirectly from
the PC's parallel port not from the target.

-Bill