AVR-Chat

Regarding below:
No other connections on the JTAG bus.
Running with internal clock at 8MHz.
I have always used a 100K pull resistor on Reset; is that too weak?

Tim

  ----- Original Message ----- 
  From: David VanHorn 
  To: AVR-Chat@yahoogroups.com 
  Sent: Thursday, January 24, 2008 2:12 PM
  Subject: Re: [AVR-Chat] Atmel JTAG-ICE MkII


  On Jan 24, 2008 3:50 PM, Tim Gilbert <tim@jeminnovation.com> wrote:
  > What's the secret to the JTAG-ICE. I've had one for several years but haven't used it because it never wants to connect consistently. I'm now on a project where it would be really nice to use but the silly thing won't talk to my ATmega128. I've programmed the JTAG fuse, what else am I missing?

  I've used the regular jtag ice with the M128 since the M128 came out.
  Not without problems and the odd day or two where it just refuses to
  work at all for no apparent reason.

  1: Is there anything else on the Jtag interface pins into the M128?
  There can be, but you need to provide resistor isolation so that the
  Jtag always wins when it wants to drive the lines.

  2: Clocking issues. If you're using a crystal or external resonator,
  BE ABSOLUTELY SURE that you don't have the clock fuse set for the low
  power "vittoz" mode oscillator. You want the full-swing version.
  Check clock osc output, it should be almost rail to rail.

  3: 10k pullup on reset, 0.1uF to ground.

  Other than that, it should just work. (for suitably loose definitions
  of "work", in this case)


   

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