AVR-Chat

paul_hvidston wrote:
> 
> Hi all,
> 
> I'm new to AVRs and I don't yet have a clear picture of the
> programming requirements/options for these devices. First a bit about
> me. I'm a consulting engineer and do hardware, software, just about
> anything I can get paid for ;-). I'm just finishing up a contract
> designing an ARM 7 core into an ASIC, I've used PICs in the past
> (never really liked them) and would like to use the Atmel devices in
> future projects (where appropriate). Hopefully some kind members can
> help set me straight here. Here's a few starter questions.
> 
> 1) From reading the chip documentation, it appears that the "fuse" and
> "lock" bits can be erased/reprogrammed. Am I correct?

All fuse and lock bits can be set (programmed to zero) with any programming
method.

> 2) Some devices in the family require a parallel programming algorithm
> in order to configure the fuse bits. For others, the fuse bits
> can/must be programmed via a serial algorithm. Yes? What cheap
> programmers to people recommend? Which ones can handle the fuse bits?
> I've seen interesting offerings from Sparc Fun Electronics
> (www.sparkfun.com). Any comments?

While any fuse/lock bit can be easily programmed 0 (set), clearing
bits (set to 1) is trickier.

Lock bits can only be cleared with a chip erase. A chip erase will
not touch the fuse bits.

If you clear the SPIEN fuse bit, you'll be locked out of ISP programming.

If you clear the JTAGEN fuse bit, you'll be locked out of JTAG programming.

If you clear both those, the only way you can get back in is to use a
12V parallel programmer.

Some later devices have 12V serial programming that may overcome
some of these problems IIRC.

> 3) It looks like only some of the newer devices support JTAG? What is
> the easiest/cheapest way to do in-circuit debugging? Are people using
> gdb (or printfs and LEDs)?

JTAG needs 4 or more wires, but the newest debug-wire method programs
thru the reset line iirc (only on later devices).

Atmel JTAG ICE or a clone of it is cheapest/easiest way for in-circuit
debugging. AVR Studio is free and controls it.

Avarice is the usual way to get gdb to control the jtag ice.

I've made gdb control the jtag ice direct, but the patches aren't ready for release.

> 4) The AT90S2313 appears to have been replaced by the ATtiny2313. Is
> the new device available and sound, or is the old device the one to use?

Think the old one is discontinued.

> Thanks for listening
> 
> Paul
> California