16 bit js virtual machine implementation
Virtual CPU use:
- RAM memory (memory size can be changed). Flat model, 0x0000 - 0xFFFF (Up to 64Kb).
- Internal registers memory (access only via registers).
Flash memory now not used.
Actual information can be found here.
- IP - Instruction pointer. Register value contains memory address of next command for executing.
- AC - Accumulator.
- SP - Stack pointer. Register value contains memory address of stack head.
- Rx - some of general purpose registers.
After CPU start IP register contain 0x0000 address, fetch instruction from RAM and start executing.
After CPU start SP register contain RAM memory size - 2 address.
After push some data SP value decreased by 2 bytes and after pop - increased by 2 bytes.
Actual information can be found here.
| Opcode | Command | Arguments | Sample | Description |
|---|---|---|---|---|
| 0x00 | NOP |
No operation | ||
| 0x?? | PUSH |
0x???? |
PUSH 0x1234 |
Push 16 bit constant to stack |
| 0x?? | PUSH |
Rx |
PUSH R4 |
Push register value to stack |
| 0x?? | POP |
Rx |
POP R1 |
Pop value from stack to register |
| 0xFF | HLT |
Halt |