78 lines
1.5 KiB
Markdown
78 lines
1.5 KiB
Markdown
# Uxn
|
|
|
|
A [stack-based VM](https://wiki.xxiivv.com/site/uxn.html), written in ANSI C.
|
|
|
|
## Assembly Syntax
|
|
|
|
### Write
|
|
|
|
- `;variable`, automatically assign an address to a label.
|
|
- `:const FFCF`, manually assign an address to a label.
|
|
- `@label`, assign the current address to a label.
|
|
|
|
### Read
|
|
|
|
- `,literal`, push label value to stack, prefixed with `LIT LEN`.
|
|
- `.pointer`, push label value to stack.
|
|
|
|
### Special
|
|
|
|
- `( comment )`, toggle parsing on/off.
|
|
- `|0010`, move to position in the program.
|
|
- `"hello`, push literal bytes for word "hello".
|
|
- `#04`, a zero-page address, equivalent to `,0004`.
|
|
|
|
### Operator modes
|
|
|
|
- `,1234 ,0001 ADD^`, 16-bits operators have the short flag `^`.
|
|
- `,12 ,11 GTH JMP?`, conditional operators have the cond flag `?`.
|
|
|
|
```
|
|
( hello world )
|
|
|
|
;iterator
|
|
|
|
|0100 @RESET
|
|
|
|
@word1 "hello_world ( len: 0x0b )
|
|
|
|
@loop
|
|
,00 IOW ( write to device#0 )
|
|
,incr JSR ( increment itr )
|
|
,word1 ,strlen JSR ( get strlen )
|
|
NEQ ,loop ROT JSR? ( loop != strlen )
|
|
|
|
BRK
|
|
|
|
@strlen
|
|
,0001 ADD^ LDR
|
|
RTS
|
|
|
|
@incr
|
|
,iterator LDR
|
|
,01 ADD
|
|
,iterator STR
|
|
,iterator LDR
|
|
RTS
|
|
|
|
|c000 @FRAME BRK
|
|
|d000 @ERROR BRK
|
|
|FFFA .RESET .FRAME .ERROR
|
|
```
|
|
|
|
## TODOs
|
|
|
|
- short variable
|
|
- Implement signed flag to operators.
|
|
- On-screen debugger.
|
|
- Auto-advance ldr?
|
|
- Getting rid of IOR/IOW would be nice..
|
|
|
|
## 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/
|