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# Uxn
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A stack-based VM, written in ANSI C.
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## Build
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```
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cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn
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```
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2021-01-29 14:35:59 -05:00
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2021-01-29 20:49:10 -05:00
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## Assembly Syntax
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### Write
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- `;variable`, set a label to an assigned address
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- `:const`, set a label to a constant short
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- `@label`, set a label to an address
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### Read
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- `,literal`, push label value to stack
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- `.pointer`, read label value
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### Special
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- `( comment )`, toggle parsing on/off
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- `|0010`, move to position in the program
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2021-01-31 00:31:49 -05:00
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2021-01-29 14:35:59 -05:00
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```
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2021-02-04 21:25:49 -05:00
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;value ( alloc a zero-page variable )
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@0010 ( start at page 1 )
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,03 ,02 ADD ,05 EQU
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,there ROT JMC
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2021-02-01 17:49:09 -05:00
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:here
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( when not equal )
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,ee
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BRK
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:there
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( when is equal )
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,ff
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BRK
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```
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2021-02-01 14:58:47 -05:00
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## Mission
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2021-02-04 00:53:56 -05:00
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### Assembler
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2021-02-03 14:30:18 -05:00
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- Catch overflow/underflow
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- Jumps should be relative
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### CPU
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- Pointers/Literals
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- A Three-Way Decision Routine(http://www.6502.org/tutorials/compare_instructions.html)
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- Print word to stdout
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- Draw pixel to screen
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- Detect mouse click
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- SDL Layer Emulator
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- Build PPU
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- Add flags..
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### Devices
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- Devices each have an input byte, an output byte and two request bytes.
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2021-01-30 17:25:48 -05:00
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## Refs
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https://code.9front.org/hg/plan9front/file/a7f9946e238f/sys/src/games/nes/cpu.c
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http://www.w3group.de/stable_glossar.html
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http://www.emulator101.com/6502-addressing-modes.html
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http://forth.works/8f0c04f616b6c34496eb2141785b4454
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https://justinmeiners.github.io/lc3-vm/
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