Hi Mike! The ATmega1284P halts the CPU anyway for video memory accesses, so I'm using the same mechanism for updating the I/O memory. So, yes, it's stopping the CPU during keyboard reads.

I forgot to mention that I'm using the address lines as selectors for I/O devices. A0 selects keyboard controller (ATtiny2313), A1 selects 74HC541 buffer for reading joystick port 1, A2 is joystick port 2. This way I don't need any decoding logic for I/O and there's plenty of lines left for more devices.

Cheers! -Petri