AVR-Chat

>>> dvanhorn@dvanhorn.org 05/11/2004 2:22:25 pm >>>
>Until you accidently "disable" the ISP mode which renders your chip
>next to useless unless you have a parallel programmer to fix it. For
>some reason people don't like to talk much about this major trap for
>young players.

>I wouldn't say that so much as it just dosen't happen that often.

That's beside the point. It can and does happen.
What happens if you have a soldered an AVR part on a board and lock up
the ISP mode? - bad news.
I know people who refuse to use SMD or solder DIP AVR parts into any
board, and I must say I'm one of them. Call me paranoid, but I'm not
going to design in a non-robust ISP system into one of my designs.

>Try a PIC sometime, IIRC if you lock the code, you can no longer
reprogram 
>the part at all.
>On the AVR, you just erase the part and carry on.

PICs are the primary micro I use. You can't render a Flash PIC part
useless no matter what you program into it. There were a few exceptions
to this on specific parts, but they have long since been fixed with
silicon revisions.

>You do have to make sure that the programmer isn't running too fast
for the 
>target system, especially when working with <1 MHz clocks.

Yet another silly AVR specific thing.
I can't believe the guys who designed the AVR ISP did it in this way,
it's completely non-robust. I can imagine the laughter if I tried to
propose such a system at a design review!

ISP modes on other micros like the PIC just work. No traps.

Dave :)