go/chip8-emulator
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LoadI, JumpV0 and Random instructions

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This commit is contained in:
Jairinho 2022-02-28 12:56:16 -03:00
parent a96785461d
commit 232661bbbe
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GPG Key ID: 954589B18A21D5B6
2 changed files with 31 additions and 5 deletions
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11
chip8/chip8.go
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@ -118,10 +118,13 @@ func (emulator *Emulator) Cycle() {
} }
case 0x9: // 9xy0 - SNE Vx, Vy case 0x9: // 9xy0 - SNE Vx, Vy
emulator.SkipNotEqual(x, y) emulator.SkipNotEqual(x, y)
case 0xA: // Annn - LD I, addr case 0xA: // Annn - LD I, nnn
case 0xB: // Bnnn - JP V0, addr emulator.LoadI(nnn)
case 0xC: // Cxkk - RND Vx, byte case 0xB: // Bnnn - JP V0, nnn
case 0xD: // Dxyn - DRW Vx, Vy, nibble emulator.JumpV0(nnn)
case 0xC: // Cxkk - RND Vx, kk
emulator.Random(x, kk)
case 0xD: // Dxyn - DRW Vx, Vy, n
emulator.Draw(x, y, n) emulator.Draw(x, y, n)
case 0xE: case 0xE:
switch instruction & 0x00FF { switch instruction & 0x00FF {

25
chip8/instructions.go
View File

@ -4,6 +4,7 @@ import (
"image" "image"
"image/color" "image/color"
"image/draw" "image/draw"
"math/rand"
) )
// Clear the display. // Clear the display.
@ -161,7 +162,7 @@ func (emulator *Emulator) ShiftLeft(x uint8) {
} }
// Skip next instruction if Vx != Vy. // Skip next instruction if Vx != Vy.
//
// The values of Vx and Vy are compared, and if they are not equal, // The values of Vx and Vy are compared, and if they are not equal,
// the program counter is increased by 2. // the program counter is increased by 2.
func (emulator *Emulator) SkipNotEqual(x uint8, y uint8) { func (emulator *Emulator) SkipNotEqual(x uint8, y uint8) {
@ -170,6 +171,28 @@ func (emulator *Emulator) SkipNotEqual(x uint8, y uint8) {
} }
} }
// Set I = nnn.
//
// The value of register I is set to nnn.
func (emulator *Emulator) LoadI(nnn uint16) {
emulator.I = nnn
}
// Jump to location nnn + V0.
//
// The program counter is set to nnn plus the value of V0.
func (emulator *Emulator) JumpV0(nnn uint16) {
emulator.PC = nnn + uint16(emulator.V[0])
}
// Set Vx = random byte AND kk.
//
// The interpreter generates a random number from 0 to 255, which is then ANDed with the value kk.
// The results are stored in Vx. See instruction 8xy2 for more information on AND.
func (emulator *Emulator) Random(x uint8, kk uint8) {
emulator.V[x] = uint8(rand.Intn(0xFF)) & kk
}
// Display n-byte sprite starting at memory location I at (Vx, Vy), set VF = collision. // Display n-byte sprite starting at memory location I at (Vx, Vy), set VF = collision.
// //
// The interpreter reads n bytes from memory, starting at the address stored in I. // The interpreter reads n bytes from memory, starting at the address stored in I.