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Re: [avr-gcc-list] Target connecting problem with JTAGICE mkII

From: Graham Davies
Subject: Re: [avr-gcc-list] Target connecting problem with JTAGICE mkII
Date: Mon, 8 Nov 2004 10:02:23 -0500


This isn't really about AVR GCC is it?

Anyway, I can't see anything obviously wrong with what you're doing.  As I
make and sell an ICE interface (the AVR "ICE-Cube") there is information on
my Web site that might be useful to you, including a bit of trouble shooting

Assuming you didn't damage the ATmega16, I would suggest you check for
something else connected to the same GPIO pins as the JTAG interface uses.

The JTAGEN fuse is programmed on all Atmel MCUs when they leave the factory,
so unless you cleared it, this isn't the problem.  AVR Studio and the JTAG
ICE will manage switching between programming and OCD for you.  You can
leave the OCDEN fuse unprogrammed and it will be programmed and cleared as

What about clock speed?  The JTAG interface cannot run faster than one
quarter of the MCU clock rate.  What is it set at?  Is your target clocking
the MCU slower than the STK500?  This shouldn't affect the initial startup
of the JTAG ICE, however, as it doesn't need the clock at all to read the

If none of this helps, maybe you could clarify "JTAGICE mkII failed to
detect the target".  Is this what appears in a pop up or is it your own
description of the problem?


----- Original Message ----- 
From: "Eric Fu" <address@hidden>
To: <address@hidden>
Sent: Saturday, November 06, 2004 10:06 PM
Subject: [avr-gcc-list] Target connecting problem with JTAGICE mkII


I previously used JTAGICE mkII to download and debug ATmeg16 with STK500
and AVR Studio without problems. Now I've built my target board and
JTAGICE mkII failed to detect the target. I've checked the HW
connections and they all seemed correct. AVR Studio prompts to retry
with external reset enabled.  When I checked Yes, it stilled failed.
(The Reset signal was indeed seen on an oscilloscope). It then prompts
to use SPI to enable the JTAG interface fuse which I haven't yet done.

Before I progress further, I'd like to see if I've missed something
I'm just wondering why it is OK with STK500? (I hope I didn't damage the
ATmeg16 when I soldered it to the board)
JTAGICE mkII user's guide indicates that it is not possible to use both
OCD and programming at the same time. Is it something to do with this?
How can I control / toggle OCD and programming mode with AVR Studio?
With STK500, I don't have to do anything. The code is loaded to the chip
at start-up and automatically goes into debug mode.

Note: The ATmeg16 is a sample supplied by Atmel. So it should come with
JTAGEN fuse programmed.

Thanks in advance for any helps.

Eric Fu

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