MadMaurice
175a24c77d
Instead of doing the same bit operations on the opcode everywhere, and possibly botching it in the process, we create a datatype which has methods return often used values extracted from the opcode.
169 lines
2.6 KiB
C++
169 lines
2.6 KiB
C++
#pragma once
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#include <misc/types.h>
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#include <memory/mem_device.h>
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typedef u8 opcode_t;
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enum Flags {
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F_ZERO = 0x8,
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F_SUB = 0x4,
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F_HALF = 0x2,
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F_CARRY = 0x1,
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};
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enum AluOp : int {
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ADD = 0,
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ADC = 1,
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SUB = 2,
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SBC = 3,
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AND = 4,
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XOR = 5,
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OR = 6,
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CP = 7,
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};
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enum CC
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{
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COND_NZ = 0,
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COND_Z = 1,
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COND_NC = 2,
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COND_C = 3,
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};
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enum InterruptType : u8
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{
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INT_VBlank = 0x1,
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INT_LCDSTAT = 0x2,
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INT_Timer = 0x4,
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INT_Serial = 0x8,
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INT_Joypad = 0x10,
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INT_MASK = 0x1F,
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};
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/**
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IME - Interrupt Master Enable
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An EI instruction will enable the interrupts, but delayed. During the next instruction after EI,
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interrupts are still disabled. For this to be emulated we use a small state machine. which works as follows
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instruction EI - sets IME_SCHEDULED
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handleInterrupts -> IME_SCHEDULED to IME_ON (but no call to isr yet)
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instruction any - is IME_ON, but no chance for call to isr yet
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handleInterrupts -> is IME_ON, do a call to isr if necessary
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*/
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enum IME_state
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{
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IME_OFF,
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IME_SCHEDULED,
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IME_ON,
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};
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struct opcode {
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const opcode_t value;
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inline operator opcode_t() const
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{ return value; }
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inline u8 reg8idxlo() const
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{ return value & 0x7; }
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inline u8 reg8idxhi() const
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{ return (value >> 3) & 0x7; }
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inline u8 reg16idx() const
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{ return (value >> 4) & 0x3; }
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inline AluOp aluop() const
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{ return (AluOp)((value >> 3) & 0x7); }
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inline u8 cc() const
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{ return (value >> 3) & 0x3; }
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inline u16 rst_addr() const
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{ return (u16)(value & 0x38); }
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};
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struct Cpu_state {
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// Registers
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union {
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u16 BC;
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struct { u8 C; u8 B; };
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};
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union {
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u16 DE;
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struct { u8 E; u8 D; };
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};
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union {
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u16 HL;
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struct { u8 L; u8 H; };
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};
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u8 A;
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u16 SP;
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u16 PC;
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bool zero;
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bool subtract;
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bool halfcarry;
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bool carry;
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IME_state IME;
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u8 IE;
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u8 IF;
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bool halted;
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bool stopped;
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void setAF(u16 v);
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u16 getAF();
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u8& reg8(u8 idx);
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u16& reg16(u8 idx);
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};
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class Cpu {
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private:
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u8 readPC8();
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u16 readPC16();
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void pushStack8(u8 data);
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u8 popStack8();
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void pushStack16(u16 data);
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u16 popStack16();
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void aluop8(AluOp op, u8 lhs, u8 rhs, u8& out, bool update_carry = true);
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inline
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void aluop8(AluOp op, u8 rhs, bool update_carry = true)
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{
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aluop8(op, state.A, rhs, state.A, update_carry);
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}
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void doCall(u16 target);
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void doRet();
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bool decodeCond(u8 cc);
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bool handleInterrupts();
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void executeInstruction();
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void reset();
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public:
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Cpu(Mem_device* bus);
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Cpu_state state;
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Mem_device* bus;
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unsigned long processed_mcycles;
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void signalInterrupt(InterruptType it);
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void step();
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};
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