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https://git.sr.ht/~rabbits/uxn
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2.7 KiB
2.7 KiB
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
Assign
@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.
Write
ADD
, an opcode.#1a
, a literal byte.#12ef
, a literal short.+1a
, a literal signed byte.+12ef
, a literal signed short.-1a
, a literal signed byte(negative).-12ef
, a literal signed short(negative)..ab
, a raw byte in memory..abcd
, a raw short in memory.,literal
, push label address to stack, prefixed withLIT LEN
.
Special
( comment )
, toggle parsing on/off.|0010
, move to position in the program."hello
, push literal bytes for word "hello".=label
, helper to STR, equivalent to,label STR
, orlabel STR2
.~label
, helper to LDR, equivalent to,label LDR2
, or,label LDR2
.
Operator modes
#1234 #0001 ADD2
, 16-bits operators have the short flag2
.#12 #11 GTH JMP?
, conditional operators have the cond flag?
.+21 -03 MULS
, signed operators have the cond flagS
.ADDS2?
, modes can be combined.
( comment )
:dev/w fff9 ( const write port )
|0100 @RESET
,string ( add string pointer to stack )
@loop
DUP2 LDR IOW ( write pointer value to console )
#0001 ADD2 ( increment string pointer )
DUP2 LDR #00 NEQ ,loop ROT JMP? POP2 ( while *ptr!=0 goto loop )
BRK
@string " Hello World " ( add string to memory )
|c000 @FRAME BRK
|d000 @ERROR BRK
|FFFA .RESET .FRAME .ERROR
Emulator
Controller(dev/ctrl)
A device that works like a NES controller, each button is a bit from a single byte.
0x01
Ctrl0x02
Alt0x04
Escape0x08
Return0x10
Up0x20
Down0x40
Left0x80
Right
TODOs
- LDR/STR helpers
- Line routine
- On-screen debugger.
- Getting rid of IOR/IOW would be nice..
- Sending from the wst to the rst, balance counter?
Misc TODOs
- Includes
- Defines
- Lint, print unused labels
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/