For an Arduino bootloader, I'd like to disable the JTAG just before jumping to the user application rather than disabling the JTAG with the fuses. This way I can always use the JTAG for debugging (but I'll have to replace the bootloader when I'm done). The JTD bit is in the MCUCR register, I think this is the correct assembly code to do the job...
__asm__ __volatile__ (
"in r30,0x35\n"
"ori R30,0x80\n"
"out 0x35,r30\n"
"out 0x35,r30\n"
);
For some reason it won't assemble with "MCUCR" and I have to put the actual address of 0x35 in the code.
EDIT
Just had to add
:
:"I"(_SFR_IO_ADDR(MCUCR))
at the end to specify the IO address as an argument number. So I guess it's correct.