Simple-68008 CPU Card

Technical

• C Code
• Runs on ANSI terminal
• Load S records using S68K_02 monitor or S68K_002 plus Enhanced BASIC using 'L' command
• Run at 0x2000 with R2000 command

Gameplay

• First person shooter
• Target '@' moves around randomly
• Bullet is '-'
• Can only have one bullet flying at a time
• Animated hit

Controls

• Move around the shooter '}' with arrow keys
• Shoot using the SPACE bar
• Q to quit.

Status Bar

• Command help message
• Counts hits and misses
• Timer running

Got the monitor running on the card and added a couple of functions:

• S record loader
• Timer

Software that runs on the card:

• S68K_02 Monitor code
• Enhanced BASIC running from SRAM
• S68K_02 monitor plus Enhanced BASIC (in ROM)
• figForth

Using gcc toolchain and wrote quite a few little pieces of software

• nncurses - ANSI terminal driver that isn't ncurses
• Some simple games

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.

Miswired serial connections (TXB, RXA).

Can be fixed by wiring connections on H1.

Fixed via cuts/jumpers.

Works.

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*.

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.