Re: [avr-chat] Avrdude and JTAG / Dragon...

[Joerg Wunsch]

David Kelly <address@hidden> wrote:

>> I understand that JTAg, thanks to its very nature, allows to chain
>> devices, allowing to talk with any one dvice from a single JTAG port.
> 
> In practice I don't think the Dragon supports that.

Of course, it does.  We aren't in MSP430 land here...  (From what I've
heard, MSP430 has a crippled and incomplete JTAG implementation that
doesn't allow chaining.)

You need AVRDUDE 5.6, where you can specify -x jtagchain UB,UA,BB,BA.
UB is "units before", UA is "units after", BB is "bits before", BA is
"bits after".  Each AVR shifts by 4 bits within the JTAG chain.  So if
you've got two AVRs in one chain, depending on which AVR you are
talking to, you use "-x jtagchain 0,1,0,4", or "-x jtagchain 1,0,1,4".

The only disadvantage of that solution is that you cannot debug both
targets simultaneously.

AVR Studio offers a similar setup box somewhere.

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

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