# Uxn A [stack-based VM](https://wiki.xxiivv.com/site/uxn.html), 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. - `( 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 char 1 byte 1 short 2 } |0100 @RESET ,text1 ,print-label JSR ,text2 ,print-label JSR #ab =dev/console.byte #cdef =dev/console.short BRK @print-label ( text ) @print-label-loop DUP2 LDR =dev/console.char ( write pointer value to console ) #0001 ADD2 ( increment string pointer ) DUP2 LDR #00 NEQ ,print-label-loop ROT JMP? POP2 ( while *ptr!=0 goto loop ) POP2 RTS @text1 [ Hello World 0a00 ] ( store text with a linebreak and null byte ) @text2 [ Welcome to UxnVM 0a00 ] |c000 @FRAME |d000 @ERROR |FF00 ;dev/console Console |FFF0 .RESET .FRAME .ERROR ( vectors ) |FFF8 [ 13fd 1ef3 1bf2 ] ( palette ) ``` ## 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 - Extra frame buffer addressing? Mirror sprites? ### 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/