Simple-68008 CPU Card

About as basic as a card can get

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68008 CPU card

  • 68008 CPU
    • 32 bit internals (registers, etc)
    • 20-bit address bus (1 MB space)
    • 8-bit address bus
    • 8 or 10 MHz clock
  • 512KB SRAM
    • Can also use 128KB SRAM part
  • Up to 448KB EPROM
    • Jumpers for 28, 32 pin parts
  • 68681 Dual UART
    • (2) 6-pin FTDI connectors
    • Up to 38,400 baud
    • 6-bits of output
    • 4-bits of input
  • Reset switch and 5V power monitor
  • Two 16V8 PLDs to make configurations easier
  • 5V Power header
    • 2x4, 0..1" pitch connector
  • 95mm x 95mm (matches other Land Boards cards)

  • Working on Monitor Code

    land-boards.com06/27/2024 at 19:26 0 comments

    Starting from Hayden Kroepfl's 68k Homebrew ROM Monitor code. Used his 68680 DUART code to get card working.

    Did my own RAM test code that tests data and address lines better and quicker.

    Examine works. Help works. Deposit works.

    Run coded (not tested yet).

    My code is here.

  • Serial Port Wiring Issue

    land-boards.com06/26/2024 at 19:33 0 comments

    Miswired serial connections (TXB, RXA).

    Can be fixed by wiring connections on H1.

    Fixed via cuts/jumpers.


  • 10 MHZ Crystal Oscillator

    land-boards.com06/26/2024 at 14:29 0 comments

    Initially ran card with 8 MHz crystal can oscillator. 10 MHz oscillators were not in stock at Mouser.

    Ordered 10 MHz can oscillator and tested card. Worked good.

    Timing Analysis via Measurement and Datasheet

    Timing measurements with 8 MHz crystal oscillator showed very wide clock pulses on DS*, etc. Modern SRAM is 55 nS and modern Flash is 70 nS so the only wait states on the card can come from the DUART and it provides its own DTACK*.

  • Project Status

    land-boards.com06/24/2024 at 23:20 0 comments

    Card is running simple example code with these features

    • SRAM Tests (data and address lines verified)
    • Code running out of EPROM
    • DUART sending out data
    • Blinking LED on O2 output pin on the DUART
    • PLDs working
    • 8 MHz oscillator (ordered 10 MHz part)

    Code is in GitHub here.

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