A very small 16 bit VM loosely based on the P'' formal language.
- MicroVM supports 16 bit addresses.
- The MicroVM word is 2 bytes, it is the smallest piece of memory that can be referenced in MicroVM.
- MicroVM supports a native language with assembly like mnemonics, unlike P'' and its own six symbol language.
- MicroVM has more operators than P''.
- MicroVM is capable of IO unlike the origional P''.
- MicroVM is turing complete by design.
MicroVM's memory is made up to 65536 (or 216) cells, each cell can hold two bytes. Some operations allow you to move the reading head (also called the memory counter) allowing you to read and write to/from a specific cell.
Memory: 131 kb (131072 b)
Registers store data temporarily.
| Register | Size |
|---|---|
| Program counter | 2 bytes |
| Memory counter | 2 bytes |
| Instruction Register | 4 bytes |
Note: Instruction register requires 4 bytes to store a 2 byte opcode and a 2 byte operand.
Flags are boolean values which are set on/off based on certain conditions.
| Flag | Size | Condition |
|---|---|---|
| Zero flag | 2 bytes | Set to 1 when CPZ encounters a memory cell with value 0, set to 0 otherwise |
| Jump flag | 2 bytes | Temporarily set to 1 by jump operations, set to 0 during program cycle |
| Error flag | 2 bytes | Set to 1 when a fatal error occurs, 0 otherwise |
| Halt flag | 2 bytes | 0 by default, set to one by HLT instruction, causes the VM to halt |
Heres is a list of supported operators and their opcodes.
| OPCODE | Operator | Hex | Effect |
|---|---|---|---|
| NOP | No operation | 0x0 | No effect |
| NXT | Next cell | 0x1 | Moves memory counter forward by one |
| PRV | Previous cell | 0x2 | Moves memory counter backwards by one |
| INC | Increment | 0x3 | Increments current cell |
| DEC | Decrement | 0x4 | Decrements current cell |
| JMP | Jump | 0xB | Jumps to address in next cell |
| CPZ | Zero check | 0x9 | Checks if current cell is zero, sets zero flag to 1 on success, 0 on failure |
| JEZ | Jump if zero | 0x5 | Equivalent to JMP otherwise but only jumps if zero flag is 1 |
| JNZ | Jump if not zero | 0x6 | Equivalent to JMP otherwise but only jumps if zero flag is 0 |
| JMM | Jump cell | 0xC | Set memory counter to address in next cell |
| DSP | Display | 0x7 | Outputs current cell to screen |
| LDS | Load from screen | 0x8 | Loads data to cell |
| HLT | Halt | 0xA | Sets halt flag to 1, this causes the VM to halt |
| PUT | Put character | 0xD | Put the ASCII character corresponding to value at current memory cell on screen |
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