ATTiny85, how to fix overwritten clock pins?

Question

I'm using an ATTiny85 with an external 16MHz clock. I accidentally set pins 3 and 4 to output using pinMode() in a program and uploaded it, and now I'm getting an invalid device signature (the signature is 0) error when I try to upload a sketch.

How can I go about fixing this (if possible)?

I am using an Arduino UNO as ISP, with an external 16MHz clock and capacitors connected to pins 3 and 4, and have rechecked my wire setup multiple times.

Answer 1

Holding the chip in reset while powering it on will ensure that the pins are never reconfigured.