controller.c

#include "controller.h"

#include "memory.h"
#include "mos6502.h"

void mos6502_controller_reset(mos6502_t * mos6502) {
    size_t i;

    /* Pull RES low */
    mos6502_set_pin_res(mos6502, BIT_ZERO, false);

    /* Neutralize other inputs */
    mos6502_set_pin_clk(mos6502, BIT_ONE, false);
    mos6502_set_pin_rdy(mos6502, BIT_ONE, false);
    mos6502_set_pin_so(mos6502, BIT_ZERO, false);
    mos6502_set_pin_irq(mos6502, BIT_ONE, false);
    mos6502_set_pin_nmi(mos6502, BIT_ONE, false);

    /* Sync all inputs */
    mos6502_sync(mos6502);

    /* Toggle CLK input for 8 full cycles */
    for (i = 0; i < 16; i++) {
        mos6502_set_pin_clk(mos6502, !mos6502_get_pin_clk(mos6502), true);
    }

    /* Pull RES high and sync */
    mos6502_set_pin_res(mos6502, BIT_ONE, true);
}

void mos6502_controller_step(mos6502_t * mos6502, mos6502_memory_t * memory) {

    /* Toggle CLK input and sync */
    mos6502_set_pin_clk(mos6502, !mos6502_get_pin_clk(mos6502), true);

    /* Access memory only after rising clock edge */
    if (mos6502_get_pin_clk(mos6502)) {
        unsigned short addr = mos6502_get_pin_ab(mos6502);

        if (mos6502_get_pin_rw(mos6502) == BIT_ZERO) {

            /* Write memory from data bus */
            mos6502_memory_write(memory, addr, mos6502_get_pin_db(mos6502));
        } else {

            /* Read memory into data bus and sync */
            mos6502_set_pin_db(mos6502, mos6502_memory_read(memory, addr), true);
        }
    }
}

void mos6502_controller_run(mos6502_t * mos6502, mos6502_memory_t * memory, size_t cycles) {
    size_t i;

    /* Each step is a half-cycle */
    for (i = 0; i < cycles; i++) {
        mos6502_controller_step(mos6502, memory);
        mos6502_controller_step(mos6502, memory);
    }
}