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Re: [avr-chat] Avrdude and JTAG / Dragon...
From: |
Joerg Wunsch |
Subject: |
Re: [avr-chat] Avrdude and JTAG / Dragon... |
Date: |
Sat, 28 Feb 2009 08:06:42 +0100 (MET) |
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. ;-)