74 lines
1.5 KiB
Markdown
74 lines
1.5 KiB
Markdown
# Dumb8-CPU
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Continuing my exploration of the lower-level world...
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This project is the implementation of a CPU in a high-level language, C. It aims to have a reduced (minimalist) instruction set and still be Turing complete.
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## How to test
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You can run a test program like that. I'll try making a developer's manual so one can make its own programs using the custom assembly here.
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`das` is the Dumb8 Assembler, which converts `.asm` files to `.bin` CPU executables. `dumb8` is the CPU emulator.
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```
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make
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./das program.asm
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./dumb8 program.bin
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```
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## Technical specifications
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- 8-bit processing unit
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- RISC (reduced instruction set computer)
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- 8 general purpose registers (labeled Rx)
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- 1 input port, 1 output port (via getchar and putchar)
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- Turing-completeness: bitwise and arithmetic operations
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## Instruction set reference (for programmers)
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```
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; Move register RY to register RX
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MOV RX, RY
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; Put value X in register RX
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PUT RX, X
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; Arithmetic operations. Result stored in RX
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ADD RX, RY
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SUB RX, RY
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MUL RX, RY
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DIV RX, RY
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; Bitwise operations stored in RX
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OR RX, RY
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AND RX, RY
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XOR RX, RY
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; Output RX to screen
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OUT RX
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; Input RX from keyboard
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IN RX
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; Jump to memory offset ADDR (decimal)
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JMP ADDR
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; Jump to memory offset ADDR (decimal) if equal flag is set by previous comparison
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JEQ ADDR
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; Compare RX and RY, sets equal flag if true
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CMP RX, RY
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; No operation; does nothing
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NOP
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; Halts the processing unit
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HLT
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```
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## Known bugs
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- (possibly) JEQ is inop
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- If you find one, please open an issue.
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