Andys Colecovision site - Hardware

Useful links :-

• Main PCB circuit diagram
• Controller circuit diagram
• Coleco ADAM and ColecoVision Related Schematics

If you want to build an add-on for a Colecovision system, you need to consider where it could connect and what existing add-ons there are.

We can extend Colecovision at these points :-

• Cartridge socket. 2x15 pin 0.1" edge-connector on motherboard. Has +5V, GND, address bus, data base, 4x 8KB chip-enables. Chip-enable assumed to imply a read operation. Bank switching options
  • No bank switching
  • MegaCart bank switching
    • 8000-BFFF is fixed area
    • touch address FFxx to set bank at C000-FFFF
    • Not clear if fixed area can be mapped (again) into C000-FFFF
  • Ultimate SD bank switching
    • Hybrid bank switching
      • touch BF80-BFBF to set 16KB R/O bank at C000-FFFF
      • touch BFC0-BFFF to set 8KB R/O bank at C000-DFFF and 8KB W/O bank at E000-FFFF (note that there is a forum post which says these are swapped around)
      • touching certain areas interpreted as commands to CPU onboard cartridge.
    • 30k/1k bank switching mode
      • 8000-F7FF fixed 30k area
      • F800-FBFF 1k banking window
      • FC00-FDFF banking area, select 1 of 512 1k blocks to be visible in the window
      • FE00-FEFF communicate to onboard CPU
      • FF00-FFFF additional unbanked ROM
• Expansion slot. Has +5V, GND and full Z80 signal set. 2x30 pin 0.1" edge-connector on expansion. Physically awkward.
• 2 controllers. 2 controller enable lines (one for joystick L,R,U,D and Fire 1, one for keypad and Fire 2), one will always be asserted, both controllers get the same one. 5 sense lines from each controller. Physical construction of controller means you should never see L+R or U+D at the same time, although electrically, this can occur. Possibly some sense logic to detect if joystick is connected. Due to use of resistors, its not clear what the voltages actually are, probably not TTL or LVTTL. No +5V or GND available. Need external power source, which would presumably be battery, and so we'd also need step-up circuitry, such as APE9202 or S8V3A or 5V DC to DC Step Up - 1xAA or NCP1402-3.3V Step-Up breakout or NCP1402 or UV10F3. Need opto-couplers?

If an add-on can be made pass-through, it can plug in to the Colecovision, and existing add-ons can plug in to it. To do this requires some care to co-exist electrically, and logically. This is why I list the bank-switching options above.