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Remove breaks,update readme, Chip8 creation method

master
arnaucube 3 years ago
parent
commit
dd363ee615
3 changed files with 13 additions and 29 deletions
  1. +3
    -1
      README.md
  2. +9
    -26
      chip8/chip8.go
  3. +1
    -2
      main.go

+ 3
- 1
README.md

@ -2,11 +2,13 @@
CHIP-8 emulator written in Go.
*(Done with the Rust implementation: https://github.com/arnaucube/chip8-rs)*
https://en.wikipedia.org/wiki/CHIP-8
### Usage
```
go run main.go -file roms/invaders.c8
./go-chip8 -file roms/invaders.c8
```
![](screenshots/s00.png)

+ 9
- 26
chip8/chip8.go

@ -37,7 +37,8 @@ type Chip8 struct {
}
// Initialize registers and memory
func (c *Chip8) Initialize() {
func NewChip8() Chip8 {
c := Chip8{}
c.pc = 0x200
c.opcode = 0
c.index = 0
@ -46,6 +47,7 @@ func (c *Chip8) Initialize() {
for i := 0; i < len(fontSet); i++ {
c.memory[i] = fontSet[i]
}
return c
}
// EmulateCycle emulates the chip8 cycle
@ -59,7 +61,6 @@ func (c *Chip8) EmulateCycle() {
// Decode Opcode
// https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
// http://www.multigesture.net/wp-content/uploads/mirror/goldroad/chip8_instruction_set.shtml
switch c.opcode & 0xF000 {
case 0x0000:
switch c.opcode & 0x000F {
@ -70,26 +71,22 @@ func (c *Chip8) EmulateCycle() {
}
c.pc += 2
c.DrawFlag = true
break
case 0x000E:
// 00EE Returns from a subroutine
c.sp--
c.pc = c.stack[c.sp]
c.pc += 2
break
default:
fmt.Printf("Unknown opcode [0x0000]: 0x%X\n", c.opcode)
}
case 0x1000:
// 1NNN Jumps to address NNN
c.pc = nnn
break
case 0x2000:
// 2NNN Calls subroutine at NNN
c.stack[c.sp] = c.pc
c.sp++
c.pc = nnn
break
case 0x3000:
// 3XNN Skips the next instruction if VX equals NN. (Usually
// the next instruction is a jump to skip a code block)
@ -97,7 +94,6 @@ func (c *Chip8) EmulateCycle() {
c.pc += 2
}
c.pc += 2
break
case 0x4000:
// 4XNN Skips the next instruction if VX doesn't equal NN.
// (Usually the next instruction is a jump to skip a code
@ -106,25 +102,21 @@ func (c *Chip8) EmulateCycle() {
c.pc += 2
}
c.pc += 2
break
case 0x5000:
// 5XY0 Skips the next instruction if VX equals VY. (Usually
// the next instruction is a jump to skip a code block)
if c.v[x] != c.v[y] {
if c.v[x] == c.v[y] {
c.pc += 2
}
c.pc += 2
break
case 0x6000:
// 6XNN Sets VX to NN
c.v[x] = nn
c.pc += 2
break
case 0x7000:
// 7XNN Adds NN to VX. (Carry flag is not changed)
c.v[x] += nn
c.pc += 2
break
case 0x8000:
switch c.opcode & 0x000F {
case 0x0000:
@ -153,14 +145,13 @@ func (c *Chip8) EmulateCycle() {
}
c.v[x] += c.v[y]
c.pc += 2
break
case 0x0005:
// 0x8XY5 VY is subtracted from VX. VF is set to 0 when
// there's a borrow, and 1 when there isn't
if c.v[x] > c.v[y] {
c.v[0xF] = 0x1
c.v[0xF] = 1
} else {
c.v[0xF] = 0x0
c.v[0xF] = 0
}
c.v[x] -= c.v[y]
c.pc += 2
@ -178,9 +169,9 @@ func (c *Chip8) EmulateCycle() {
// 0x8XY7 Sets VX to VY minus VX. VF is set to 0 when
// there's a borrow, and 1 when there isn't
if c.v[y] > c.v[x] {
c.v[0xF] = 0x1
c.v[0xF] = 1
} else {
c.v[0xF] = 0x0
c.v[0xF] = 0
}
c.v[x] = c.v[y] - c.v[x]
c.pc += 2
@ -209,7 +200,6 @@ func (c *Chip8) EmulateCycle() {
// ANNN set index to NNN position
c.index = nnn
c.pc += 2
break
case 0xB000:
// BNNN Jumps to the address NNN plus V0
c.pc = nnn + uint16(c.v[0])
@ -252,7 +242,6 @@ func (c *Chip8) EmulateCycle() {
c.DrawFlag = true
c.pc += 2
break
case 0xE000:
switch c.opcode & 0x00FF {
case 0x009E:
@ -263,7 +252,6 @@ func (c *Chip8) EmulateCycle() {
c.pc += 2
}
c.pc += 2
break
case 0x00A1:
// EXA1 Skips the next instruction if the key stored in
// VX isn't pressed. (Usually the next instruction is a
@ -275,7 +263,6 @@ func (c *Chip8) EmulateCycle() {
default:
fmt.Printf("Unknown opcode [0xE000]: 0x%X\n", c.opcode)
}
break
case 0xF000:
switch c.opcode & 0x00FF {
case 0x0007:
@ -315,13 +302,11 @@ func (c *Chip8) EmulateCycle() {
// represented by a 4x5 font
c.index = uint16(c.v[x]) * 5
c.pc += 2
break
case 0x0033:
c.memory[c.index] = c.v[x] / 100
c.memory[c.index+1] = (c.v[x] / 10) % 10
c.memory[c.index+2] = (c.v[x] / 100) % 10
c.pc += 2
break
case 0x0055:
// FX55 Stores V0 to VX (including VX) in memory
// starting at address I. The offset from I is
@ -336,15 +321,13 @@ func (c *Chip8) EmulateCycle() {
// from memory starting at address I. The offset from I
// is increased by 1 for each value written, but I
// itself is left unmodified
for i := uint16(0); i < uint16(x)+1; i++ {
for i := uint16(0); i <= uint16(x); i++ {
c.v[i] = c.memory[c.index+i]
}
c.pc += 2
break
default:
fmt.Printf("Unknown opcode [0xF000]: 0x%X\n", c.opcode)
}
break
default:
fmt.Printf("Unknown opcode: 0x%X\n", c.opcode)
}

+ 1
- 2
main.go

@ -20,8 +20,7 @@ type SdlEmulator struct {
// NewSdlEmulator creates a new SdlEmulator
func NewSdlEmulator(w, h int, zoom int32) SdlEmulator {
var c chip8.Chip8
c.Initialize()
c := chip8.NewChip8()
window, err := sdl.CreateWindow("go-chip8", sdl.WINDOWPOS_UNDEFINED,
sdl.WINDOWPOS_UNDEFINED, int32(w)*zoom, int32(h)*zoom, sdl.WINDOW_SHOWN)

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