Usage#
#include <Z/constants/pointer.h> /* Z_NULL */
#include <Z80.h>
#define CYCLES_PER_FRAME 69888
#define CYCLES_AT_INT 24
#define CYCLES_PER_INT 32
#define ROM_SIZE 0x4000 /* 16 KiB */
#define MEMORY_SIZE 0x8000 /* 32 KiB */
typedef struct {
void* context;
zuint8 (* read)(void *context);
void (* write)(void *context, zuint8 value);
zuint16 assigned_port;
} Device;
typedef struct {
zusize cycles;
zuint8 memory[65536];
Z80 cpu;
Device* devices;
zusize device_count;
} Machine;
Device *machine_find_device(Machine *self, zuint16 port)
{
zusize index = 0;
for (; index < device_count; index++)
if (self->devices[index]->assigned_port == port)
return &self->devices[index];
return Z_NULL;
}
static zuint8 machine_cpu_read(Machine *self, zuint16 address)
{
return address < MEMORY_SIZE ? self->memory[address] : 0xFF;
}
static void machine_cpu_write(Machine *self, zuint16 address, zuint8 value)
{
if (address >= ROM_SIZE && address < MEMORY_SIZE)
self->memory[address] = value;
}
static zuint8 machine_cpu_in(Machine *self, zuint16 port)
{
Device *device = machine_find_device(self, port);
return device != Z_NULL ? device->read(device->context) : 0xFF;
}
static void machine_cpu_out(Machine *self, zuint16 port, zuint8 value)
{
Device *device = machine_find_device(self, port);
if (device != Z_NULL) device->write(device->context, value);
}
void machine_initialize(Machine *self)
{
self->cpu.context = self;
self->cpu.fetch_opcode =
self->cpu.fetch =
self->cpu.nop =
self->cpu.read = (Z80Read )machine_cpu_read;
self->cpu.write = (Z80Write)machine_cpu_write;
self->cpu.in = (Z80Read )machine_cpu_in;
self->cpu.out = (Z80Write)machine_cpu_out;
self->cpu.halt = Z_NULL;
self->cpu.nmia = Z_NULL;
self->cpu.inta = Z_NULL;
self->cpu.int_fetch = Z_NULL;
self->cpu.ld_i_a = Z_NULL;
self->cpu.ld_r_a = Z_NULL;
self->cpu.reti = Z_NULL;
self->cpu.retn = Z_NULL;
self->cpu.hook = Z_NULL;
self->cpu.illegal = Z_NULL;
self->cpu.options = Z80_MODEL_ZILOG_NMOS;
/* Create and initialize devices... */
}
void machine_power(Machine *self, zboolean state)
{
if (state)
{
self->cycles = 0;
memset(self->memory, 0, 65536);
}
z80_power(&self->cpu, state);
}
void machine_reset(Machine *self)
{
z80_instant_reset(&self->cpu);
}
void machine_run_frame(Machine *self)
{
/* CPU cycles before the INT signal */
self->cycles += z80_execute(&self->cpu, CYCLES_AT_INT - self->cycles);
/* CPU cycles during the INT signal */
z80_int(&self->cpu, Z_TRUE);
self->cycles += z80_run(&self->cpu, (CYCLES_AT_INT + CYCLES_PER_INT) - self->cycles);
z80_int(&self->cpu, Z_FALSE);
/* CPU cycles after the INT signal */
self->cycles += z80_execute(&self->cpu, CYCLES_PER_FRAME - self->cycles);
self->cycles -= CYCLES_PER_FRAME;
}