AVR-Chat

On Mon, Dec 13, 2004 at 06:47:22AM -0800, Larry Barello wrote:

> One last tid-bit: the reset line has no protection diodes to V+ This
> is the only pin without protection since it needs to be able to
> respond to +12v for parallel programming mode.
> 
> For most situations this isn't a big deal, but most people simply
> run that line out to their ISP header without any protection.  I
> never do any more than put a 1-4k resister in line, but having a
> diode on the connector side of the resister connected to V+ would
> guarantee a safe header.

See Atmel App Note AVR040: EMC Design Considerations, Figure 10 on
page 14.  This is the circuit I use on my MAVRIC boards and it
provides the same level of protection for /RESET as on the other I/O
pins.

-Brian
-- 
Brian Dean
BDMICRO - ATmega128 Based MAVRIC Controllers
http://www.bdmicro.com/