frodo-wii/Src/CPU1541.h

/*
 *  CPU1541.h - 6502 (1541) emulation (line based)
 *
 *  Frodo (C) 1994-1997,2002 Christian Bauer
 */

#ifndef _CPU_1541_H
#define _CPU_1541_H

#include "CIA.h"
#include "C64.h"


// Set this to 1 if the 6502 PC should be represented by a real pointer
#ifndef FRODO_SC
#ifndef PC_IS_POINTER
#define PC_IS_POINTER 1
#endif
#endif

// Set this to 1 for more precise CPU cycle calculation
#ifndef PRECISE_CPU_CYCLES
#define PRECISE_CPU_CYCLES 0
#endif


// Interrupt types
enum {
	INT_VIA1IRQ,
	INT_VIA2IRQ,
	INT_IECIRQ
	// INT_RESET (private)
};


class C64;
class Job1541;
class C64Display;
struct MOS6502State;


// 6502 emulation (1541)
class MOS6502_1541 {
public:
	MOS6502_1541(C64 *c64, Job1541 *job, C64Display *disp, uint8 *Ram, uint8 *Rom);

#ifdef FRODO_SC
	void EmulateCycle(void);			// Emulate one clock cycle
#else
	int EmulateLine(int cycles_left);	// Emulate until cycles_left underflows
#endif
	void Reset(void);
	void AsyncReset(void);				// Reset the CPU asynchronously
	void GetState(MOS6502State *s);
	void SetState(MOS6502State *s);
	uint8 ExtReadByte(uint16 adr);
	void ExtWriteByte(uint16 adr, uint8 byte);
	void CountVIATimers(int cycles);
	void NewATNState(void);
	void IECInterrupt(void);
	void TriggerJobIRQ(void);
	bool InterruptEnabled(void);

	MOS6526_2 *TheCIA2;		// Pointer to C64 CIA 2

	uint8 IECLines;			// State of IEC lines (bit 7 - DATA, bit 6 - CLK)
	bool Idle;				// true: 1541 is idle

private:
	uint8 read_byte(uint16 adr);
	uint8 read_byte_io(uint16 adr);
	uint16 read_word(uint16 adr);
	void write_byte(uint16 adr, uint8 byte);
	void write_byte_io(uint16 adr, uint8 byte);

	uint8 read_zp(uint16 adr);
	uint16 read_zp_word(uint16 adr);
	void write_zp(uint16 adr, uint8 byte);

	void jump(uint16 adr);
	void illegal_op(uint8 op, uint16 at);
	void illegal_jump(uint16 at, uint16 to);

	void do_adc(uint8 byte);
	void do_sbc(uint8 byte);

	uint8 *ram;				// Pointer to main RAM
	uint8 *rom;				// Pointer to ROM
	C64 *the_c64;			// Pointer to C64 object
	C64Display *the_display; // Pointer to C64 display object
	Job1541 *the_job;		// Pointer to 1541 job object

	union {					// Pending interrupts
		uint8 intr[4];		// Index: See definitions above
		unsigned long intr_any;
	} interrupt;

	uint8 n_flag, z_flag;
	bool v_flag, d_flag, i_flag, c_flag;
	uint8 a, x, y, sp;
#if PC_IS_POINTER
	uint8 *pc, *pc_base;
#else
	uint16 pc;
#endif

#ifdef FRODO_SC
	uint32 first_irq_cycle;

	uint8 state, op;		// Current state and opcode
	uint16 ar, ar2;			// Address registers
	uint8 rdbuf;			// Data buffer for RMW instructions
	uint8 ddr, pr;			// Processor port
#else
	int borrowed_cycles;	// Borrowed cycles from next line
#endif

	uint8 via1_pra;		// PRA of VIA 1
	uint8 via1_ddra;	// DDRA of VIA 1
	uint8 via1_prb;		// PRB of VIA 1
	uint8 via1_ddrb;	// DDRB of VIA 1
	uint16 via1_t1c;		// T1 Counter of VIA 1
	uint16 via1_t1l;		// T1 Latch of VIA 1
	uint16 via1_t2c;		// T2 Counter of VIA 1
	uint16 via1_t2l;		// T2 Latch of VIA 1
	uint8 via1_sr;		// SR of VIA 1
	uint8 via1_acr;		// ACR of VIA 1
	uint8 via1_pcr;		// PCR of VIA 1
	uint8 via1_ifr;		// IFR of VIA 1
	uint8 via1_ier;		// IER of VIA 1

	uint8 via2_pra;		// PRA of VIA 2
	uint8 via2_ddra;	// DDRA of VIA 2
	uint8 via2_prb;		// PRB of VIA 2
	uint8 via2_ddrb;	// DDRB of VIA 2
	uint16 via2_t1c;		// T1 Counter of VIA 2
	uint16 via2_t1l;		// T1 Latch of VIA 2
	uint16 via2_t2c;		// T2 Counter of VIA 2
	uint16 via2_t2l;		// T2 Latch of VIA 2
	uint8 via2_sr;		// SR of VIA 2
	uint8 via2_acr;		// ACR of VIA 2
	uint8 via2_pcr;		// PCR of VIA 2
	uint8 via2_ifr;		// IFR of VIA 2
	uint8 via2_ier;		// IER of VIA 2
};

// 6502 state
struct MOS6502State {
	uint8 a, x, y;
	uint8 p;			// Processor flags
	uint16 pc, sp;

	uint8 intr[4];		// Interrupt state
	bool instruction_complete;
	bool idle;

	uint8 via1_pra;		// VIA 1
	uint8 via1_ddra;
	uint8 via1_prb;
	uint8 via1_ddrb;
	uint16 via1_t1c;
	uint16 via1_t1l;
	uint16 via1_t2c;
	uint16 via1_t2l;
	uint8 via1_sr;
	uint8 via1_acr;
	uint8 via1_pcr;
	uint8 via1_ifr;
	uint8 via1_ier;

	uint8 via2_pra;		// VIA 2
	uint8 via2_ddra;
	uint8 via2_prb;
	uint8 via2_ddrb;
	uint16 via2_t1c;
	uint16 via2_t1l;
	uint16 via2_t2c;
	uint16 via2_t2l;
	uint8 via2_sr;
	uint8 via2_acr;
	uint8 via2_pcr;
	uint8 via2_ifr;
	uint8 via2_ier;
};



/*
 *  Trigger job loop IRQ
 */

#ifdef FRODO_SC
inline void MOS6502_1541::TriggerJobIRQ(void)
{
	if (!(interrupt.intr[INT_VIA2IRQ]))
		first_irq_cycle = the_c64->CycleCounter;
	interrupt.intr[INT_VIA2IRQ] = true;
	Idle = false;
}
#else
inline void MOS6502_1541::TriggerJobIRQ(void)
{
	interrupt.intr[INT_VIA2IRQ] = true;
	Idle = false;
}
#endif


/*
 *  Count VIA timers
 */

inline void MOS6502_1541::CountVIATimers(int cycles)
{
	unsigned long tmp;

	via1_t1c = tmp = via1_t1c - cycles;
	if (tmp > 0xffff) {
		if (via1_acr & 0x40)	// Reload from latch in free-run mode
			via1_t1c = via1_t1l;
		via1_ifr |= 0x40;
	}

	if (!(via1_acr & 0x20)) {	// Only count in one-shot mode
		via1_t2c = tmp = via1_t2c - cycles;
		if (tmp > 0xffff)
			via1_ifr |= 0x20;
	}

	via2_t1c = tmp = via2_t1c - cycles;
	if (tmp > 0xffff) {
		if (via2_acr & 0x40)	// Reload from latch in free-run mode
			via2_t1c = via2_t1l;
		via2_ifr |= 0x40;
		if (via2_ier & 0x40)
			TriggerJobIRQ();
	}

	if (!(via2_acr & 0x20)) {	// Only count in one-shot mode
		via2_t2c = tmp = via2_t2c - cycles;
		if (tmp > 0xffff)
			via2_ifr |= 0x20;
	}
}


/*
 *  ATN line probably changed state, recalc IECLines
 */

inline void MOS6502_1541::NewATNState(void)
{
	uint8 byte = ~via1_prb & via1_ddrb;
	IECLines = (byte << 6) & ((~byte ^ TheCIA2->IECLines) << 3) & 0x80	// DATA (incl. ATN acknowledge)
		| (byte << 3) & 0x40;											// CLK
}


/*
 *  Interrupt by negative edge of ATN on IEC bus
 */

inline void MOS6502_1541::IECInterrupt(void)
{
	ram[0x7c] = 1;

	// Wake up 1541
	Idle = false;
}


/*
 *  Test if interrupts are enabled (for job loop)
 */

inline bool MOS6502_1541::InterruptEnabled(void)
{
	return !i_flag;
}

#endif