Internal pullups overpower input file values after 1 cycle

[jeffpc]

I tried to use the --input option to toggle MCU pins to get pin change interrupts. It looks like that an input file asserting a pin low works for only 1 cycle (1us @ 1MHz) before the pullup resistor overpowers it. In other words, it looks like _avr_vcd_input_timer in simavr sets the value but the next timestep simavr "forgets" that there is an external logic-low input and sets the pin high because of the pullup.