I've had a not-completely original idea that I've been kicking around for a while...

The Commodore 64 was designed to allow an alternate processor (specifically the Z80) to take over the bus and replace the 6510 running the computer.

Here's a link to a schematic of the CP/M cartridge: http://www.zimmers.net/anonftp/pub/c...matics-big.gif

From the explanation given, a lot of the circuitry is to work around how the Z80 wants to see the world (RAM available at $0000) vs how the 6510 does ($0000 and $0001 make up a special I/O port, and generally, code doesn't go in zero page.)

With that in mind, it *seems* like I can get away with connecting the 3.5 directly to the bus, especially since the 3.5 is 5V tolerant. In the cp/m cart schematic, only 31 pins from the 6510 bus are brought over to the Z80, so that looks good too.

What I don't know: Is it ok to just say, connect the cartridge port pin for A15 to a digital pin on the Teensy? Do I need anything in the middle or any kind of decoupling capacitor connected anywhere? I guess what I'm getting at is, timing issues aside, is this as easy as it looks?

Basically, my overall goal is to write a program on the Teensy that makes things happen on the C64... A dumb example: a space invaders clone that runs on the teensy but uses the C64's graphics, video, keyboard, etc.