Re: Connecting IO

As "Bob & Linda Gardner" <[email protected]> wrote:

>I have two Mega8s that need to communicate a couple of bits of IO
>between them.  I have this running now it it seems to work fine.  I
>am connecting outputs from one processor to inputs on a second
>processor.  I am currently using a 470 ohm resistor in series which
>each point.  Do I need this protection or can I just connect the IO
>points together directly?

If you ensure that at most one of the controllers is going to drive
each of the lines for output, you can connect them directly.

Btw., the SPI feature is intended for communication like this.

OTOH, the 470 Ohm resistors won't hurt much.  Even if you assume some
50 pF of capacitive load, the cutoff frequency of the resulting
lowpass filter is still several MHz.  With 100 Ohms, you're completely
safe even for full-speed SPI.
-- 
J"org Wunsch					       Unix support engineer
[email protected]        http://www.interface-systems.de/~j/