forked from HFO4/gameboy.live
/
cpu.go
302 lines (264 loc) · 6.16 KB
/
cpu.go
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package gb
import (
"fmt"
"log"
"github.com/andydotxyz/fynegameboy/util"
)
type CPU struct {
Registers Registers
Flags Flags
Halt bool
}
/*
Registers
16bit Hi Lo Name/Function
AF A - Accumulator & Flags
BC B C BC
DE D E DE
HL H L HL
SP - - Stack Pointer
PC - - Program Counter/Pointer
*/
type Registers struct {
A byte
B byte
C byte
D byte
E byte
F byte
HL uint16
PC uint16
SP uint16
}
/*
The Flag Register (lower 8bit of AF register)
Bit Name Set Clr Expl.
7 zf Z NZ Zero Flag
6 n - - Add/Sub-Flag (BCD)
5 h - - Half Carry Flag (BCD)
4 cy C NC Carry Flag
3-0 - - - Not used (always zero)
Contains the result from the recent instruction which has affected flags.
*/
type Flags struct {
Zero bool
Sub bool
HalfCarry bool
Carry bool
// IME - Interrupt Master Enable Flag (Write Only)
// 0 - Disable all Interrupts
// 1 - Enable all Interrupts that are enabled in IE Register (FFFF)
InterruptMaster bool
PendingInterruptEnabled bool
}
func (core *Core) initCPU() {
log.Println("[Core] Initialize CPU flags and registers")
//Initialize flags with default value.
core.CPU.Flags.Zero = true
core.CPU.Flags.Sub = false
core.CPU.Flags.HalfCarry = true
core.CPU.Flags.Carry = true
core.CPU.Flags.InterruptMaster = false
/*
Initialize register after BIOS
AF=$01B0
BC=$0013
DE=$00D8
HL=$014D
Stack Pointer=$FFFE
*/
core.CPU.Registers.A = 0x01
core.CPU.Registers.B = 0x00
core.CPU.Registers.C = 0x13
core.CPU.Registers.D = 0x00
core.CPU.Registers.E = 0xD8
core.CPU.Registers.F = 0xB0
core.CPU.Registers.HL = 0x014D
core.CPU.Registers.PC = 0x0100
core.CPU.Registers.SP = 0xFFFE
}
/*
Execute the next OPCode and return used CPU clock
*/
func (core *Core) ExecuteNextOPCode() int {
opcode := core.ReadMemory(core.CPU.Registers.PC)
core.CPU.Registers.PC++
return core.ExecuteOPCode(opcode)
}
/*
Break execution and print register/dump memory information for debug purpose.
*/
func (core *Core) Break(code byte) {
af := core.CPU.getAF()
bc := core.CPU.getBC()
de := core.CPU.getDE()
hl := core.CPU.Registers.HL
sp := core.CPU.Registers.SP
pc := core.CPU.Registers.PC - 1
lcdc := core.Memory.MainMemory[0xFF40]
IF := core.Memory.MainMemory[0xFF0F]
IE := core.Memory.MainMemory[0xFFFF]
core.Memory.Dump("memory.dump")
log.Printf("[Debug] \n\033[34m[OP:%s]\nAF:%04X BC:%04X DE:%04X HL:%04X SP:%04X\nPC:%04X LCDC:%02X IF:%02X IE:%02X IME:%t\nLCD:%X \033[0m", OPCodeFunctionMap[code].OP, af, bc, de, hl, sp, pc, lcdc, IF, IE, core.CPU.Flags.InterruptMaster, core.DebugControl)
}
/*
Execute given OPCode and return used CPU clock
*/
func (core *Core) ExecuteOPCode(code byte) int {
if OPCodeFunctionMap[code].Clock != 0 {
if core.DebugControl == core.CPU.Registers.PC-1 && core.Debug {
core.Break(code)
_, err := fmt.Scanf("%X", &core.DebugControl)
if err != nil {
core.CPU.Registers.PC = 0
}
}
var extCycles int
extCycles = OPCodeFunctionMap[code].Func(core)
return OPCodeFunctionMap[code].Clock + extCycles
} else {
if core.Debug {
core.Break(code)
}
log.Fatalf("Unable to resolve OPCode:%X PC:%X\n", code, core.CPU.Registers.PC-1)
return 0
}
}
/*
Get 16bit parameter after OpCode
*/
func (core *Core) getParameter16() uint16 {
b1 := uint16(core.ReadMemory(core.CPU.Registers.PC))
b2 := uint16(core.ReadMemory(core.CPU.Registers.PC + 1))
core.CPU.Registers.PC += 2
return b2<<8 | b1
}
/*
Set value of register A
*/
func (core *Core) setA(val byte) {
core.CPU.Registers.A = val
}
/*
Set value of register B
*/
func (core *Core) setB(val byte) {
core.CPU.Registers.B = val
}
/*
Set value of register C
*/
func (core *Core) setC(val byte) {
core.CPU.Registers.C = val
}
/*
Set value of register D
*/
func (core *Core) setD(val byte) {
core.CPU.Registers.D = val
}
/*
Set value of register D
*/
func (core *Core) setE(val byte) {
core.CPU.Registers.E = val
}
/*
Set value of register H
*/
func (core *Core) setH(val byte) {
core.CPU.Registers.HL &= 0x00FF
core.CPU.Registers.HL |= ((uint16(val) << 8) & 0xFF00) // OR in the desired mask
}
/*
Set value of register L
*/
func (core *Core) setL(val byte) {
core.CPU.Registers.HL &= 0xFF00
core.CPU.Registers.HL |= (uint16(val) & 0x00FF) // OR in the desired mask
}
/*
Get 8bit parameter after opcode
*/
func (core *Core) getParameter8() byte {
b := core.ReadMemory(core.CPU.Registers.PC)
core.CPU.Registers.PC += 1
return b
}
/*
Get value of AF register
*/
func (cpu *CPU) getAF() uint16 {
return uint16(cpu.Registers.A)<<8 | uint16(cpu.Registers.F)
}
/*
Set value of AF register
*/
func (cpu *CPU) setAF(val uint16) {
cpu.Registers.A = byte((val & 0xFF00) >> 8)
cpu.Registers.F = byte(val & 0xFF)
}
/*
Set value of BC register
*/
func (cpu *CPU) setBC(val uint16) {
cpu.Registers.B = byte((val & 0xFF00) >> 8)
cpu.Registers.C = byte(val & 0xFF)
}
/*
Set value of DE register
*/
func (cpu *CPU) setDE(val uint16) {
cpu.Registers.D = byte((val & 0xFF00) >> 8)
cpu.Registers.E = byte(val & 0xFF)
}
/*
Get value of BC register
*/
func (cpu *CPU) getBC() uint16 {
return uint16(cpu.Registers.B)<<8 | uint16(cpu.Registers.C)
}
/*
Get value of DE register
*/
func (cpu *CPU) getDE() uint16 {
return uint16(cpu.Registers.D)<<8 | uint16(cpu.Registers.E)
}
/*
Update Low 8bit of AF register
TODO: maybe this operation is useless in non-debug mode.
*/
func (cpu *CPU) updateAFLow() {
newAF := cpu.Registers.F
if cpu.Flags.Zero {
newAF = util.SetBit(newAF, 7)
} else {
newAF = util.ClearBit(newAF, 7)
}
if cpu.Flags.Sub {
newAF = util.SetBit(newAF, 6)
} else {
newAF = util.ClearBit(newAF, 6)
}
if cpu.Flags.HalfCarry {
newAF = util.SetBit(newAF, 5)
} else {
newAF = util.ClearBit(newAF, 5)
}
if cpu.Flags.Carry {
newAF = util.SetBit(newAF, 4)
} else {
newAF = util.ClearBit(newAF, 4)
}
cpu.Registers.F = newAF
}
/*
Compare two values and set flags
*/
func (cpu *CPU) Compare(val1 byte, val2 byte) {
cpu.Flags.Zero = (val1 == val2)
cpu.Flags.Carry = (val1 > val2)
cpu.Flags.HalfCarry = ((val1 & 0x0f) > (val2 & 0x0f))
cpu.Flags.Sub = true
cpu.updateAFLow()
}