This is a "micro" implementation of the Motorola 68000. The board being used here is an iceFUN with a Lattice iCE40 HX8K FPGA.

Website: https://www.mikekohn.net/micro/micro_x86_68000_fpga.php

Implemented:

add
adda
addi
addq
and
andi
asl
asr
bcc
bchg
bclr
bset
bsr
bra
btst
clr
cmp
cmpa
cmpi
eor
eori
jmp
jsr
lea
lsl
lsr
move
mov from SR
move to SR
move to CCR
moveq
neg
ori
rol
ror
rts
sub
suba
subi
subq
swap
trap #num

Not implemented:

asl <ea>
asr <ea>
exg
lsl <ea>
lsr <ea>
pea
rol <ea>
ror <ea>
Scc

The trap instruction is used to put the CPU in a halted state. Using trap #1, the CPU will go into the ERROR state while any other value will put the CPU into the HALTED state.

This implementation of the Motorola 68000 has 4 banks of memory.

• Bank 0: RAM (4096 bytes)
• Bank 1: ROM (4096 bytes loaded from rom.txt)
• Bank 2: Peripherals
• Bank 3: RAM (4096 bytes)

On start-up by default, the chip will load a program from a AT93C86A 2kB EEPROM with a 3-Wire (SPI-like) interface but wll run the code from the ROM. To start the program loaded to RAM, the program select button needs to be held down while the chip is resetting.

• 0x8000: input from push button
• 0x8002: SPI TX
• 0x8004: SPI RX
• 0x8006: SPI CTRL
• 0x8010: ioport0 output (in my test case only 1 pin is connected)
• 0x8012: MIDI note value (60-96) to play a tone on the speaker or 0 to stop
• 0x8014: ioport1