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

Assembly Syntax

ADD, an opcode.
@label, assign the current address to a label.
;variable 2, assign an address to a label automatically.
:const 1a2b, assign an address to a label manually.
&macro { x 2 y 2 }, define a macro named macro.
#1a, a literal byte/short.
+1a, a literal signed byte/short.
-1a, a literal signed byte/short(negative).
.ab, a raw byte/short in memory.
,literal, push label address to stack, prefixed with LIT LEN.
=label, helper to STR, equivalent to ,label STR, or label STR2.
~label, helper to LDR, equivalent to ,label LDR2, or ,label LDR2.
|0010, move to position in the program.
<23, move the program position 23 bytes backward.
>12, move the program position 12 bytes forward.
( comment ), toggle parsing on/off.
[ 0123 abcd ], write shorts to memory.
[ Hello World ], write text to memory.

Operator modes

#1234 #0001 ADD2, 16-bits operators have the short flag 2.
#12 #11 GTH JMP?, conditional operators have the cond flag ?.
+21 -03 MULS, signed operators have the cond flag S.
ADDS2?, modes can be combined.

( hello world )

&Console { pad 8 stdio 1 }

|0100 @RESET 
	
	,text1 ,print-label JSR ( print to console )

BRK

@print-label ( text )

	@cliloop
		DUP2 LDR =dev/console.stdio              ( write pointer value to console )
		#0001 ADD2                               ( increment string pointer )
		DUP2 LDR #00 NEQ ,cliloop ROT JMP? POP2  ( while *ptr!=0 goto loop )
	POP2
		
RTS                 

@text1 [ Hello World ] <1 .00 ( add text to memory, return 1 byte, add null byte )

|c000 @FRAME
|d000 @ERROR 

|FF00 ;dev/console Console

|FFF0 .RESET .FRAME .ERROR
|FFF8 [ f3f0 f30b f30a ] ( palette )

Emulator

Controller(dev/ctrl)

A device that works like a NES controller, each button is a bit from a single byte. Press h to toggle debugger.

0x01 Ctrl
0x02 Alt
0x04 Escape
0x08 Return
0x10 Up
0x20 Down
0x40 Left
0x80 Right

TODOs

OS Boot Disk

Load external disk in disk2
Build hex editor
Build sprite editor

Examples

Basics:
- Simple drag/drop redraw
- Window basics with open/close drag/drop redraw
- Example of button pointing to a subroutine
GUI:
- Line routine

Assembler

Includes
Defines

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