I've been searching around in circles to find a procedure to reset an ATMega16 to its factory programmed fuse bits state. I used an ISP programmer to lock up the chip to further programming. The chips arrived set to use the 1 MHz internal RC osc and all attempts by me to try to change just the clock options thru ISP to enable an external crystal result in locking up the chip.
From what I've read it seems it might be possible to use a JTAG programmer to program both the SPIEN and JTAGEN fuse bits, but the ATMEga16 spec sheet is extraordinarily glib on whether or how this can be done. How does the factory reprogram locked devices ? If both JTAGEN and SPIEN are disabled, how can further programming attempts succeed at all ?
Do I have to just throw away this chip ??? :x