mahamooda:
I have changed the fuse to "Ext. Clock; Start-up time: 6 CK + 65ms" by using the ICSP interface near the reset button. Now, I am not able to restore the fuse to "Ext. Crystal Osc. 8.0- MHz; Start-up time: 16K CK + 65ms" as the board has become unresponsive. (I was using AVRISPmkII programmer to access the mega2560 board through ICSP interface). Any suggestions please ?
The Mega2560 board has the external crystal/resonator... Therefore this cannot be the issue with the main uC... Either internal OR external clock should work. The ACRISPmkII is a fine programmer, so either you got the fuses really tangled to the point of requiring an HV programmer or something else is weird. Perhaps one of the guru members will stop by and offer an idea.
Ray