RebeccaBlue
Member
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/cbm/schematics/cartridges/c64/cpm/schematics-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.
Thanks!
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/cbm/schematics/cartridges/c64/cpm/schematics-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.
Thanks!