an emulator for chip8 to practice c/c++
roms from https://github.com/kripod/chip8-roms
| 0x0000 | |
|---|---|
| Interpreter | |
| ------ | ---------------- |
| 0x0200 | |
| ------ | ---------------- |
| ------ | ---------------- |
| 0x0EA0 | |
| ------ | ---------------- |
| Call stack | |
| ------ | ---------------- |
| 0x0F00 | |
| ------ | ---------------- |
| Display refresh | |
| ------ | ---------------- |
| 0x1000 |
16 8-bit registers:
- V0 - VF
- VF doubles as flag for some instructions, so not for general use
- Address register (I)
- 16-bits wide
The stack is only used to store return addresses when subroutines are called.
The original RCA 1802 version allocated 48 bytes for up to 12 levels of nesting;[12] modern implementations usually have more.[13][14]
Two timers:
- Delay timer: Can be set and read
- Sound timer: When non-zero, beep
Both count down at 60 Hz, until they reach 0
16 inputs, 0 - F
- 2468: directional input
- Three opcodes detect input (see below)
Resolution: 64x32 Color: Monochrome
- Graphics are drawn to the screen solely by drawing sprites.
- Sprites are 8 px wide, from 1-16 px high.
- Sprite pixels are XOR'ed with screen pixels
- The carry flag (VF) is set to 1 if any screen pixels are flipped from set to unset when a sprite is drawn and set to 0 otherwise. This is used for collision detection.
Beeps when sound timer is nonzero.
35 opcodes
- All two bytes long, big-endian
NNN: address NN: 8-bit constant N: 4-bit constant X and Y: 4-bit register identifier PC : Program Counter I : 16bit register (For memory address) (Similar to void pointer) VN: One of the 16 available variables. N may be 0 to F (hexadecimal) There have been many implementations of the CHIP-8 instruction set since 1978. The following specification is based on the SUPER-CHIP specification from 1991 (but without the additional opcodes that provide extended functionality), as that is the most commonly encountered extension set today. Footnotes denote incompatibilities with the original CHIP-8 instruction set from 1978.