I have used my JTAGICE MKII for approx. 2 years now with larger AVR's, and now I have made a PCB with a tiny45.
First I connected the ISP with my STK500 and enabled the DWEN fuse.
Then I connected the JTAG Debugwire and started some debug sessions. It worked as expected.
Then I wanted to theck the system clock frequency and made a program loop toggling a port pin.
It was running only 8 MHz, so I had to reprogram the fuses to make it run 16MHz.
I pressed the button in debug mode to disable the DWEN
fuse. But the ISP from STK500 did not work.
I also thied high voltage programming. It did not work, I read a signature of FF FF FF.
I could no longer debug either.
To avoid waisting more time I desoldered the SMD chip and mounted a new one.
I used ISP to set the fuses and program my test program.
Now the timing was correct, so I enabled the DWEN fuse.
But the debugwire does not work, I get a dialogbox when trying to start a debug session saying:
"Unable to connect to device. This could be caused by reset line circuitry or disabled debugWIRE interface. Make sure the reset line is free before continuing."
When attempting to start the debug session, the reset line toggles.
I tested that the normal JTAG connects and works fine with a Mega128.
I use Studio 4.12 SP4 build 498.
Any Ideas ?