I'm having some pretty good luck with the ATtiny12 on the STK500 board, but after changing fuse bits, changing them back seems a bit of a challenge. Here's where I am...
I can program the '12 fine with ISP serial method (I'm using Mac OS X unix with the GNU uisp tool for downloading & interrogation )
I have written several assembly programs and everything works fine.
I can query the fuse bits, and I see the results fine
I can change the fuse-bits eg. from the default 0x52 to 0x72.
After changing the fuse-bits to turn of ISP, as expected, the ISP interactions result in "unable to enter programming mode"
To change them, I understood that I need to use "High-Voltage Programming" and so I followed the hookups in the STK500 doc's to wire it for that. I tell uisp to use hivoltage with -dhiv option.
I can then download programs just fine still - using the high voltage serial pgm.
I can query the fuses - and the session goes well enough, but the report is that the fuse bit low byte (the only byte in there) is at 0xFF
I can issue a high voltage fuse-bit write and it tells me that it has successfully written 0x52 back in to the part, but it still reads as 0xFF in high voltage, and when going back to ISP programming, ISP seems to still be behaving as if it's 0x52 (SPI port off).
Can anyone offer any info on changing Fuse Bits after you have turned of the SPI port? Have you ever changed it back? Should this work... or is the Fuse-Bit some destructive process perhaps...
Any clarification appreciated...
Ross.