130 lines
2.9 KiB
Markdown
130 lines
2.9 KiB
Markdown
# 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
|
|
|
|
### Define
|
|
|
|
- `@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.
|
|
- `¯o { x 2 y 2 }`, define a macro named `macro`.
|
|
|
|
### Program
|
|
|
|
- `ADD`, push an opcode.
|
|
- `.address`, push label address to memory.
|
|
- `,literal`, push label address to stack, prefixed with `LIT LEN`.
|
|
- `#1a`, push a literal byte/short.
|
|
- `+1a`, push a literal signed byte/short.
|
|
- `-1a`, push a literal signed byte/short(negative).
|
|
- `|0010`, move to position in the program.
|
|
|
|
### Helpers
|
|
|
|
- `=label`, helper to STR, equivalent to `,label STR`, or `label STR2`.
|
|
- `~label`, helper to LDR, equivalent to `,label LDR2`, or `,label LDR2`.
|
|
|
|
### Blocks
|
|
|
|
- `( 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 JSR2
|
|
,text2 ,print-label JSR2
|
|
#ab =CNSL.byte
|
|
#cdef =CNSL.short
|
|
|
|
BRK
|
|
|
|
@print-label ( text )
|
|
|
|
NOP
|
|
( send ) DUP2 LDR =CNSL.char
|
|
( incr ) #0001 ADD2
|
|
( loop ) DUP2 LDR #00 NEQ ^print-label MUL JMPS
|
|
POP2
|
|
|
|
RTS
|
|
|
|
@text1 [ Hello 20 World 0a00 ] ( text with linebreak and null bytes )
|
|
@text2 [ Welcome 20 to 20 UxnVM 0a00 ]
|
|
|
|
|c000 @FRAME
|
|
|d000 @ERROR
|
|
|
|
|FF00 ;CNSL Console
|
|
|
|
|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
|
|
- Local loops
|
|
- Jump helpers
|
|
|
|
## 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/
|