WozMon is a machine code monitor written by Steve Wozniak in 6502 assembly for the apple 1 [1,2].

This is a port written in motorolla 68000 assembly for the Sega Mega Drive/Genesis.
Additionally it contains subroutines to interact with the VDP (Video Display Processor).

The program does run on original Sega Mega Drive II hardware, tested with a Mega Everdrive Pro.
Unfortunately I do not have a Saturn Keyboard to test if it works correctly.
Fortunately some emulators such as BlastEm do have keyboard support.
Running the code on linux should be as easy as:

git clone https://github.com/EythorE/sega_wozmon.git
cd sega_wozmon

# On linux this does all the manual labour and boots the rom in an emulator
make run

Get a Sega Mega Drive emulator with Saturn Keyboard support

wget https://www.retrodev.com/blastem/blastem64-0.6.2.tar.gz
tar -xf blastem64-0.6.2.tar.gz

Get a compatible assembler

wget http://sun.hasenbraten.de/vasm/release/vasm.tar.gze
tar -xf vasm.tar.gz
# compile vasmm68k_mot
cd vasm
make CPU=m68k SYNTAX=mot
cd ..

Assemble the ROM

./vasm/vasmm68k_mot -chklabels -nocase -Fbin main.asm -L wozmon.l -o wozmon.gen

Emulate

# From the menu go into 'Settings' -> 'System' and change 'IO port 2 Device' to 'Saturn Keyboard'.
# To enable keyboard capture; press the right CTRL.
# load wozmon.gen
./blastem64-0.6.2/blastem wozmon.gen

Compiler:
http://sun.hasenbraten.de/vasm/

Great emulator with debuging capabilities and support for keyboards:
Select saturn keyboard as the input device on port 2 and
press right ctrl to capture keyboard when the code is running.
https://www.retrodev.com/blastem/

Wozmon:
[1] https://www.sbprojects.net/projects/apple1/wozmon.php
Explained by Ben Eater:
[2] https://youtu.be/SpG8rgI7Hec?si=jlzcbweJRtWATUog
https://eater.net/6502

Mega Drive tutorials and code:
https://github.com/BigEvilCorporation/megadrive_sampless ; Most of the supporting code
https://www.chibiakumas.com/68000/genesis.php ; More code, including good video tutorials

Saturn keyboard reference and code:
https://www.plutiedev.com/saturn-keyboard

Mega Drive architecture:
https://www.copetti.org/writings/consoles/mega-drive-genesis/

References for the VDP:
https://segaretro.org/Sega_Mega_Drive/VDP_general_usage
https://md.railgun.works/index.php?title=VDP

References for Motorola 68000 assembly:
https://mrjester.hapisan.com/04_MC68/Index.html
Full reference documentation: http://wpage.unina.it/rcanonic/didattica/ce1/docs/68000.pdf
Cheatsheet: https://www.chibiakumas.com/68000/CheatSheet.pdf

Awesome links:
https://github.com/And-0/awesome-megadrive