nesemu/cpu/cpu.h

//
// Created by william on 10/15/23.
//

#ifndef CPU_CPU_H
#define CPU_CPU_H

#include <stdbool.h>
#include "memory.h"

// Reference: https://www.nesdev.org/wiki/Status_flags
#define CPU_STATUS_CARRY_MASK 0x01
#define CPU_STATUS_ZERO_MASK 0x02
#define CPU_STATUS_INTERRUPT_DISABLE_MASK 0x04
#define CPU_STATUS_DECIMAL_MASK 0x08
#define CPU_STATUS_B_MASK 0x10
#define CPU_STATUS_OVERFLOW_MASK 0x40
#define CPU_STATUS_NEGATIVE_MASK 0x80

#define CPU_STACK_ADDR 0x0100

// Reference: https://www.nesdev.org/obelisk-6502-guide/registers.html
typedef struct cpu {
    address program_counter;
    byte stack_pointer;
    byte accumulator;
    byte x;
    byte y;
    byte status;
    bool oam_dma_triggered;
    bool nmi_requested;

    unsigned int busy_cycle_count;
} CPU;

CPU *cpu_get_state();

/**
 * Gets a flag from the CPU registers.
 * 
 * @param system The system
 * @param mask The flag mask
 * @return The value of the flag.
 */
bool cpu_get_flag(byte mask);

/**
 * Sets a flag in the CPU registers.
 * 
 * @param system The system
 * @param mask The flag mask
 * @param set If the flag is set or not
 */
void cpu_set_flag(byte mask, bool set);

/**
 * Gets the next byte in the program.
 * Increases the system program counter.
 * 
 * @param system The system 
 * @return The value of the next byte.
 */
byte cpu_get_next_byte();

/**
 * Gets the next word in the program.
 * Increases the system program counter by 2.
 * 
 * @param system The system
 * @return The value of the next word.
 */
word cpu_get_next_word();

/**
 * Pushes a byte in to the stack.
 * 
 * @param system The system 
 * @param value The value to push to the stack
 */
void cpu_stack_push(byte value);

/**
 * Pushes the execution context to the stack.
 * This includes the program counter and the CPU status.
 * 
 * @param system The system
 */
void cpu_stack_push_context();

/**
 * Pops a byte from the stack.
 * 
 * @param system The system 
 * @return The value of the byte
 */
byte cpu_stack_pop();

/**
 * Pops an execution context from the stack and overwrite the current context.
 * This includes the program counter and the CPU status.
 * 
 * @param system The system 
 */
void cpu_stack_pop_context();

/**
 * Adds wait cycles to the CPU.
 * 
 * @param cycle_count The number of cycle to wait 
 */
void cpu_add_cycles(unsigned int cycle_count);

void cpu_trigger_oam_dma();
void cpu_trigger_nmi();

#endif //CPU_CPU_H