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Uxn

A stack-based VM, written in ANSI C.

Setup

If you wish to build your own emulator, you can create a new instance of Uxn like:

#include "uxn.h"

Uxn u;

if(!bootuxn(&u))
	return error("Boot", "Failed");
if(!loaduxn(&u, argv[1]))
	return error("Load", "Failed");
if(!init())
	return error("Init", "Failed");

evaluxn(u, u->vreset); /* Once on start */
evaluxn(u, u->vframe); /* Each frame

Uxambly

Read more in the Uxambly Guide.

( hello world )

@RESET 
	
	,text1 ,print-label JSR2
	,text2 ,print-label JSR2
	#ab =Console.byte
	#cdef =Console.short

BRK

@print-label ( text )
	
	$loop NOP
		( send ) DUP2 LDR =Console.char
		( incr ) #0001 ADD2
		( loop ) DUP2 LDR #00 NEQ ^$loop MUL JMPS 
	POP2

RTN    

@text1 [ Welcome 20 to 20 UxnVM 0a00 ]
@text2 [ Hello 20 World 0a00 ] 

|c000 @FRAME
|d000 @ERROR 

|FF00 ;Console { pad 8 char 1 byte 1 short 2 }

|FFF0 .RESET .FRAME .ERROR ( vectors )
|FFF8 [ 13fd 1ef3 1bf2 ] ( palette )

TODOs

OS Boot Disk

Load external disk in disk2
Build hex editor

Assembler

Includes
Defines
Jump helpers
Don't brk when return stack is not zeroed
LDRS should load from the zeropage?
Keep ref counts in macros
A fast way(2 bytes) to read from the zero page #aa LDR.

Macros

&RTS { RSW JMP } 
&JSR { PRG WSR JMP }

Notes

Conditional Jumping

I've considered automatically popping an amount of items from the stack equal to the offset between the opcode's push/pop to make the stack length more predictable, and making the pattern JMP? POP2 unecessary, but that idea would make DUP? unusable. That change was reverted.

Palettes

[ 6a03 4a0d aa0c ], purple/cyan
[ a1f3 a14d a16c ], grey-pink/teal

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/

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Uxn