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Nitron

Nitron is a 32-bit stack based virtual machine. Its goal is to work as an operating system for microcontrollers and maybe even desktop computers.

Instead of being restricted to its own memory, it has access to the host machine's memory. This means it can easily interact with the MMIO you may find on microcontrollers, meaning you can do low level programming in it.

Ideas

• Have a numbered drive system like I have for the resource manager in Arkas Engine
• Have a read only file system stored on the microcontroller flash (same file system as Arkas Engine archives)
• Allow the user to connect an SD card reader/writer via GPIO to save their work

GitHub

• https://github.com/mesyeti/nitron

CPU

The opcode takes up the lower 7 bits of the instruction. If the highest bit is set to 1, then the 32 bit value after the instruction is pushed to the stack before the instruction is executed.

Registers

Registers:

• 0 - General purpose
• 1 - General purpose
• 2 - General purpose
• 3 - General purpose
• 4 - General purpose
• 5 - General purpose
• 6 - General purpose
• 7 - General purpose

Instructions

• 0x00 - NOP
• 0x01 - ADD
• 0x02 - SUB
• 0x03 - MUL
• 0x04 - DIV
• 0x05 - MOD
• 0x06 - R2D
• 0x07 - D2R
• 0x08 - DUP
• 0x09 - OVER
• 0x0A - DROP
• 0x0B - ROT
• 0x0C - AREA
• 0x0D - READ
• 0x0E - WRITE
• 0x0F - JUMP
• 0x10 - JNZ
• 0x11 - HALT
• 0x12 - ECALL
• 0x13 - REG
• 0x14 - WREG
• 0x15 - READ8
• 0x16 - WRITE8
• 0x17 - READ16
• 0x18 - WRITE16
• 0x19 - JZ
• 0x20 - DIVMOD
• 0x21 - EQU
• 0x22 - LESS
• 0x23 - GREATER
• 0x24 - LE
• 0x25 - GE
• 0x26 - NEG
• 0x27 - AND
• 0x28 - XOR
• 0x29 - OR
• 0x2A - NOT
• 0x2B - SWAP
• 0x2C - CALL
• 0x2D - RET
• 0x2E - FARCALL

System calls

The higher 16 bits is the section, the lower 16 bits is the call.

Section 0x0000 - User calls

This section has some space for user defined calls

Section 0x0001 - IO

• 0x00 - Print character: ( ch -- )
• 0x01 - Print string: ( string len -- )
• 0x02 - Print hex: ( num -- )
• 0x03 - Input char: ( -- ch )
• 0x04 - Print null terminated string ( string -- )
• 0x05 - Input line: ( string* maxLength -- )
• 0x06 - Print decimal: ( num -- )

Section 0x0002 - Memory

• 0x00 - Alloc: ( size -- ptr )
• 0x01 - Realloc ( ptr size -- ptr )
• 0x02 - Free ( ptr -- )

Section 0x0003 - VM

• 0x00 - Dump: ( -- )
• 0x01 - Get user calls amount ( -- size )
• 0x02 - Removed
• 0x03 - Error to string ( error -- str* )
• 0x04 - Dump memory: ( addr size -- )
• 0x05 - Get memory usage: ( -- used total )
• 0x06 - Set area pointer: ( ptr -- )
• 0x07 - Get area pointer: ( -- ptr )
• 0x08 - Nothing ( -- )
• 0x09 - Run file ( path -- success )

Section 0x0004 - Assembler

• 0x00 - Assemble ( completion? source assembler* -- size success )
  • Source must be null terminated
• 0x01 - New assembler ( -- asm*)
• 0x02 - Free assembler ( asm* -- )
• 0x03 - Get assembler binary pointer ( asm* -- bin* )
• 0x04 - Set assembler area ( area size asm* -- )
• 0x05 - Get assembler data pointer ( asm* -- data* )
• 0x06 - Set assembler data pointer ( data* asm* -- )
• 0x07 - Set assembler binary ( bin* size asm* -- )
• 0x08 - Free incomplete assembler references ( asm* -- )
• 0x09 - Reset assembler binary length ( asm* -- )
• 0x0a - Set assembler binary pointer ( bin* asm* -- )
• 0x0b - Extend assembler binary ( size asm* -- success )
• 0x0c - Set assembler mode ( code=0,data=1 asm* -- )
• 0x0d - Reset assembler binary ( asm* -- )
• 0x0e - Freeze assembler labels ( asm* -- )
• 0x0f - Get assembler binary ( asm* -- bin* )

Section 0x0005 - Filesystem

• 0x00 - Read file ( path -- size contents* success )
• 0x01 - Read text file ( path -- contents* success )
• 0x02 - Write file ( path size data -- success )
• 0x03 - Write text file ( path str -- success )

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