Am I correct that to disable the reset pin of Attiny85, and use it as an IO pin, I need to disable the reset fuse bit(RSTDSBL)?

If so, should my RSTDSBL bit be 1 (assuming 1 = yes, disable)?

I am a little confused, because it looks like my reset pin got disabled only after I set the RSTDSBL bit to 0 (which is reverse of the logic I expected).

  • 1
    \$\begingroup\$ Please not that after programming the fuse you CAN NOT use an in-circuit programmer any more. \$\endgroup\$
    – Vorac
    Nov 9, 2015 at 13:27

1 Answer 1


AVR fuses use negative logic; 1 means the fuse is unprogrammed/unset, while 0 means it's programmed/set. Thus, if the documentation says to program RSTDISBL, that means you should set it to 0.

  • \$\begingroup\$ Thanks for the response. Now it makes all sense and can go to bed! (I wilt accept it as the answer in 8 min; apparently I can't accept it so soon). \$\endgroup\$
    – Adam Lee
    Nov 9, 2015 at 11:43

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