Initial support for Genesis/Megadrive PBC mode. VDP still needs Mode 4 to be useful.

1 files changed, 221 insertions, 0 deletions

diff --git a/sms.c b/sms.c
new file mode 100644
index 0000000..f94806d
--- /dev/null
+++ b/sms.c
@@ -0,0 +1,221 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include "sms.h"
+#include "blastem.h"
+#include "render.h"
+#include "util.h"
+
+static void *memory_io_write(uint32_t location, void *vcontext, uint8_t value)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	if (location & 1) {
+		sms->io.ports[0].control = ~(value << 5 & 0x60);
+		sms->io.ports[1].control = ~(value << 3 & 0x60);
+		io_data_write(sms->io.ports, value << 1, z80->current_cycle);
+		io_data_write(sms->io.ports + 1, value >> 1, z80->current_cycle);
+	} else {
+		//TODO: memory control write
+	}
+	return vcontext;
+}
+
+static uint8_t hv_read(uint32_t location, void *vcontext)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	vdp_run_context(sms->vdp, z80->current_cycle);
+	uint16_t hv = vdp_hv_counter_read(sms->vdp);
+	if (location & 1) {
+		return hv;
+	} else {
+		return hv >> 8;
+	}
+}
+
+static void *sms_psg_write(uint32_t location, void *vcontext, uint8_t value)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	psg_run(sms->psg, z80->current_cycle);
+	psg_write(sms->psg, value);
+	return vcontext;
+}
+
+static void update_interrupts(sms_context *sms)
+{
+	uint32_t vint = vdp_next_vint(sms->vdp);
+	uint32_t hint = vdp_next_hint(sms->vdp);
+	sms->z80->int_pulse_start = vint < hint ? vint : hint;
+}
+
+static uint8_t vdp_read(uint32_t location, void *vcontext)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	vdp_run_context(sms->vdp, z80->current_cycle);
+	if (location & 1) {
+		sms->vdp->flags &= ~(FLAG2_VINT_PENDING|FLAG2_HINT_PENDING);
+		update_interrupts(sms);
+		return vdp_control_port_read(sms->vdp);
+	} else {
+		return vdp_data_port_read(sms->vdp);
+	}
+}
+
+static void *vdp_write(uint32_t location, void *vcontext, uint8_t value)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	vdp_run_context(sms->vdp, z80->current_cycle);
+	if (location & 1) {
+		vdp_control_port_write_pbc(sms->vdp, value);
+		update_interrupts(sms);
+	} else {
+		vdp_data_port_write_pbc(sms->vdp, value);
+	}
+	return vcontext;
+}
+
+static uint8_t io_read(uint32_t location, void *vcontext)
+{
+	z80_context *z80 = vcontext;
+	sms_context *sms = z80->system;
+	if (location == 0xC0 || location == 0xDC) {
+		uint8_t port_a = io_data_read(sms->io.ports, z80->current_cycle);
+		uint8_t port_b = io_data_read(sms->io.ports, z80->current_cycle);
+		return (port_a & 0x3F) | (port_b << 6);
+	}
+	if (location == 0xC1 || location == 0xDD) {
+		uint8_t port_a = io_data_read(sms->io.ports, z80->current_cycle);
+		uint8_t port_b = io_data_read(sms->io.ports, z80->current_cycle);
+		return (port_a & 0x40) | (port_b >> 2 & 0xF) | (port_b << 1 & 0x80) | 0x10;
+	}
+	return 0xFF;
+}
+
+static memmap_chunk io_map[] = {
+	{0x00, 0x40, 0xFF, 0, 0, 0, NULL, NULL, NULL, NULL,     memory_io_write},
+	{0x40, 0x80, 0xFF, 0, 0, 0, NULL, NULL, NULL, hv_read,  sms_psg_write},
+	{0x80, 0xC0, 0xFF, 0, 0, 0, NULL, NULL, NULL, vdp_read, vdp_write},
+	{0xC0, 0x100,0xFF, 0, 0, 0, NULL, NULL, NULL, io_read,  NULL}
+};
+
+static void set_speed_percent(system_header * system, uint32_t percent)
+{
+	sms_context *context = (sms_context *)system;
+	uint32_t old_clock = context->master_clock;
+	context->master_clock = ((uint64_t)context->normal_clock * (uint64_t)percent) / 100;
+
+	psg_adjust_master_clock(context->psg, context->master_clock);
+}
+
+static void run_sms(system_header *system)
+{
+	render_disable_ym();
+	sms_context *sms = (sms_context *)system;
+	uint32_t target_cycle = sms->z80->current_cycle + 3420*262;
+	while (!sms->should_return)
+	{
+		z80_run(sms->z80, target_cycle);
+		target_cycle = sms->z80->current_cycle;
+		vdp_run_context(sms->vdp, target_cycle);
+		psg_run(sms->psg, target_cycle);
+		target_cycle += 3420*262;
+		if (target_cycle > 0x10000000) {
+			uint32_t adjust = sms->z80->current_cycle - 3420*262*2;
+			io_adjust_cycles(sms->io.ports, sms->z80->current_cycle, adjust);
+			io_adjust_cycles(sms->io.ports+1, sms->z80->current_cycle, adjust);
+			z80_adjust_cycles(sms->z80, adjust);
+			vdp_adjust_cycles(sms->vdp, adjust);
+			sms->psg->cycles -= adjust;
+			target_cycle -= adjust;
+		}
+	}
+	sms->should_return = 0;
+	render_enable_ym();
+}
+
+static void start_sms(system_header *system, char *statefile)
+{
+	sms_context *sms = (sms_context *)system;
+	set_keybindings(&sms->io);
+	
+	z80_assert_reset(sms->z80, 0);
+	z80_clear_reset(sms->z80, 128*15);
+	
+	run_sms(system);
+}
+
+static void free_sms(system_header *system)
+{
+	sms_context *sms = (sms_context *)system;
+	vdp_free(sms->vdp);
+	z80_options_free(sms->z80->options);
+	free(sms->z80);
+	psg_free(sms->psg);
+	free(sms);
+}
+
+static uint16_t get_open_bus_value(system_header *system)
+{
+	return 0xFFFF;
+}
+
+static void request_exit(system_header *system)
+{
+	sms_context *sms = (sms_context *)system;
+	sms->should_return = 1;
+}
+
+sms_context *alloc_configure_sms(void *rom, uint32_t rom_size, void *extra_rom, uint32_t extra_rom_size, uint32_t opts, uint8_t force_region, rom_info *info_out)
+{
+	memset(info_out, 0, sizeof(*info_out));
+	sms_context *sms = calloc(1, sizeof(sms_context));
+	rom_size = nearest_pow2(rom_size);
+	uint32_t mask = rom_size >= 0xC000 ? 0xFFFF : rom_size-1;
+	memmap_chunk memory_map[] = {
+		{0x0000, 0xC000,  rom_size-1,         0, 0, MMAP_READ,                      rom,      NULL, NULL, NULL, NULL},
+		{0xC000, 0x10000, sizeof(sms->ram)-1, 0, 0, MMAP_READ|MMAP_WRITE|MMAP_CODE, sms->ram, NULL, NULL, NULL, NULL}
+	};
+	info_out->map = malloc(sizeof(memory_map));
+	memcpy(info_out->map, memory_map, sizeof(memory_map));
+	z80_options *zopts = malloc(sizeof(z80_options));
+	init_z80_opts(zopts, info_out->map, 2, io_map, 4, 15, 0xFF);
+	sms->z80 = malloc(sizeof(z80_context));
+	init_z80_context(sms->z80, zopts);
+	sms->z80->system = sms;
+	
+	char * lowpass_cutoff_str = tern_find_path(config, "audio\0lowpass_cutoff\0").ptrval;
+	uint32_t lowpass_cutoff = lowpass_cutoff_str ? atoi(lowpass_cutoff_str) : 3390;
+	
+	//TODO: Detect region and pick master clock based off of that
+	sms->normal_clock = sms->master_clock = 53693175;
+	
+	sms->psg = malloc(sizeof(psg_context));
+	psg_init(sms->psg, render_sample_rate(), sms->master_clock, 15*16, render_audio_buffer(), lowpass_cutoff);
+	
+	sms->vdp = malloc(sizeof(vdp_context));
+	init_vdp_context(sms->vdp, 0);
+	sms->vdp->system = &sms->header;
+	
+	info_out->save_type = SAVE_NONE;
+	info_out->name = strdup("Master System Game");
+	
+	setup_io_devices(config, info_out, &sms->io);
+	
+	sms->header.set_speed_percent = set_speed_percent;
+	sms->header.start_context = start_sms;
+	sms->header.resume_context = run_sms;
+	//TODO: Fill in NULL values
+	sms->header.load_save = NULL;
+	sms->header.persist_save = NULL;
+	sms->header.free_context = free_sms;
+	sms->header.get_open_bus_value = get_open_bus_value;
+	sms->header.request_exit = request_exit;
+	sms->header.inc_debug_mode = NULL;
+	sms->header.inc_debug_pal = NULL;
+	
+	return sms;
+}
\ No newline at end of file