AVR-Chat

--- In AVR-Chat@yahoogroups.com, David Kelly <dkelly@...> wrote:

> ... You have to have the ISP to
> put the chip in JTAG mode.

This is not true.  The ATmega32A will program and debug at the JTAG interface as delivered by Atmel.  So will all the other JTAG-capable devices of which I am aware.  JTAG is not a "mode".

> ... You have to have the ISP to
> recover from certain goofs you
> can do in JTAG mode.

The only goof you can make that will lock you out of the JTAG port is to disable JTAG by clearing the JTAGEN fuse.  This is an easy goof to avoid, unlike the infamous clock fuse goofs.

Personally, I would not bother with an ISP connector.  You can do everything that you can do with ISP using JTAG, and more.  I would consider test points on the ISP signals, plus any un-used port pins, that in dire emergency could be wired to an ISP interface.

Also, there's no need to bother with an external power-on-reset chip.  The internal one works fine.

Graham.