This question refers specifically to an ATmega328P, but probably can be generalized to most or all AVR MCUs.
Known 1: When the Data Direction Register (DDR) for a pin is set as input mode, it is still possible to write to the PORT for that pin; instead of producing an output, the value written to PORT will just change the pin between pullup and tri-state mode.
Known 2: A pin can be configured to toggle its output state along with the waveform generation module in a timer.
Question: When the DDR for a pin is configured as input, and that same pin is also configured to change state along with a timer, will the timer waveform effectively just rapidly switch the pin between tri-state and pullup modes? Or will the pin behave more reasonably, staying in tri-state/pullup according to the PORT value?
I guess the question could be restated as: Does the timer write to the PORT register in order to change the pin's state?
The only thing remotely relevant I could find in the datasheet is the following line:
...However, note that the Data Direction Register (DDR) bit corresponding to the [timer] pin must be set in order to enable the output driver.