Uxn

A stack-based VM, written in ANSI C.

Build

cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn

Assembly Syntax

Write

• ;variable, set a name to address on the zero-page
• :label, set a name to an address

Read

• ,literal, get a literal pointer
• .pointer, get a raw pointer

Special

• @0010, move to position in the program
• ( comment )

( comment )

;variable1
;variable2
;variable3

.there ( 0a 05 GTH ) JMC

:here
	< when not equal >
	ee
	BRK

:there
	< when is equal >
	ff
	BRK

Mission

Assembler

• Crash on missing label
• Catch overflow/underflow
• Constants
• Jumps should be relative

CPU

• Pointers/Literals
• A Three-Way Decision Routine(http://www.6502.org/tutorials/compare_instructions.html)
• Carry flag?
• Print word to stdout
• Draw pixel to screen
• Detect mouse click
• SDL Layer Emulator
• Build PPU
• Interrupts, vectors

16 Bit Missions

• 16 bits addressing
• jumping to subroutine should be relative
• Implement addressing
• Implement 16 bits operations

Refs

https://code.9front.org/hg/plan9front/file/a7f9946e238f/sys/src/games/nes/cpu.c http://www.w3group.de/stable_glossar.html http://www.emulator101.com/6502-addressing-modes.html http://forth.works/8f0c04f616b6c34496eb2141785b4454 https://justinmeiners.github.io/lc3-vm/