Re: [avr-chat] About JTAG...

[Joerg Wunsch]

Vincent Trouilliez <address@hidden> wrote:

> ..., but I am not quite 100% sure from the man page, if the terminal
> mode is also supported when using JTAG.

Terminal mode is supported with all supported programmer types.
However, its features might be restricted, e.g. for devices that use
page programming on the flash ROM, terminal mode cannot modify the
flash as there's no code inside to reassemble the changes into a full
page.

> The AVR datasheet does say that JTAG can access the EEPROM, just not
> sure if avrdude can/does make use of it in terminal mode.

It can, but only if you enable the OCDEN fuse (since that's what the
underlying JTAG interface requires).  Of course, you can just
temporarily enable it initially (usually, in the hfuse), modify the
EEPROM, and then turn it off again.

> 2) I understand that the program to use for debugging is "avarice".
> I looked at the man page for it, and I thiiiiink the ATmega32/Dragon
> combination is supported, ...

Sure, it is.

> 3) Does question 1) make sense at all ? I mean, when using gdb and a
> GUI to debug the program via JTAG, can't the gdb GUI display (and
> write) the contents of the EEPROM and Flash, in a similar fashion to
> avrdude's terminal mode ?

In theory, it can.  I'm not quite sure about possible bugs though.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)