[avrdude-dev] Re: How to talk to second device in JTAG chain?

[Grant Edwards]

On 2007-11-07, Eric Weddington <address@hidden> wrote:
>  
>
>> -----Original Message-----
>> From: 
>> address@hidden 
>> [mailto:address@hidden
>> rg] On Behalf Of Grant Edwards
>> Sent: Wednesday, November 07, 2007 10:20 AM
>> To: address@hidden
>> Subject: [avrdude-dev] Re: How to talk to second device in JTAG chain?
>> 
>> On 2007-11-06, Grant Edwards <address@hidden> wrote:
>> > On 2007-11-05, Joerg Wunsch <address@hidden> wrote:
>> 
>> >> The attached patch adds a -j option that allows adjusting JTAG
>> >> daisy-chain parameters. [...]
>> 
>> > Brilliant!  I'll give it a try.
>> 
>> It works just fine.  FWIW, an MSP430 is "8 bits long".  With
>> the AVR preceded by the MSP430, configuring the avrdude for 1
>> device before and 8 bits before allowed avrdude to talk to the
>> AVR.
>> 
>> The MSP430 itself will work in a chain (as long as it's first
>> in the chain -- an obnoxious/ignorant decision by TI). However,
>> the bad news is that none of the TI SW tools can tolerate any
>> other devices in the chain at all (an even _more_
>> obnoxious/ignorant decision by TI).  If you ever run into the
>> TI guys who made those decisions (IIRC it was the group in down
>> in Freising), kick them in the shins for me. ;)
>
> Sounds like you have many reasons to drop the MSP430 part and
> use a second AVR. ;-)

The MSP430 parts have their advantages.  For that particular
app, the MSP430 is quite a bit smaller and cheaper.  

In general, being able to clock the UART from 32768Hz while
having the high-speed clock and CPU completely shut down can
save a _lot_ of power.  Not having to have a high-frequency
crystal is also pretty nice.

-- 
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