In the last episode we talked about the Input side of I/O on the JJ65C02 project, which involved the Pi Pico interfacing with the PS/2 Keyboard and sending the corresponding ASCII character to the 6502, via the VIA chip. In this episode we're looking at the Output side, where the 6502 needs to send data to the Pi Pico to then send out to the VGA monitor. We'll see how the Pi Pico reads from the 8 data lines and ensures compliance with the 6502 timing diagrams. We use a simple PIO program and the Pi Pico's interrupt system to fill our output buffer on route to the VGA subsystem.

https://www.youtube.com/watch?v=-Ird9Bdk95s