Re: [avr-chat] avr-gdb, assembly, and JTAG

[Graham Davies]

Marge Coahran wrote:

> ... do I understand correctly that to use JTAG in a Linux environment, I 
> first need to use ISP once to enable the JTAGEN fuse, but thereafter the 
> fuse can remain enabled over a sequence of program and debug sessions?

No, I believe that this is incorrect.  The "default" state of the JTAG 
enable fuse is clearly stated in the device data sheet, so you could just 
look it up.  For the ATmega16 device I checked that it is "programmed", i.e. 
JTAG is enabled in devices shipped from Atmel.  So, there is no need to mess 
with this fuse and you can plunge straight in with JTAG.  I think this is 
also the case with pretty much every other JTAG-enabled device from Atmel. 
I am a big fan of JTAG and generally ignore ISP and this always seems to 
work.

By the way, I think you'll find that the ATmega16L has been replaced with 
the ATmega16A.

I'll probably get in trouble for saying this, but if your objective is to 
teach your students about the AVR, you're doing them a great disservice by 
insisting on Linux.  All these problems you're trying to clarify just don't 
exist in AVR Studio.  Admittedly, debugWIRE isn't as easy to use as JTAG, 
but you certainly don't have to rewire to high voltage programming to turn 
it on and off.

Graham.