path: root/blastem.c

#include "68kinst.h"
#include "m68k_to_x86.h"
#include "z80_to_x86.h"
#include "mem.h"
#include "vdp.h"
#include "render.h"
#include "blastem.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define CARTRIDGE_WORDS 0x200000
#define RAM_WORDS 32 * 1024
#define Z80_RAM_BYTES 8 * 1024
#define MCLKS_PER_68K 7
#define MCLKS_PER_Z80 15
//TODO: Figure out the exact value for this
#define MCLKS_PER_FRAME (MCLKS_LINE*262)
#define CYCLE_NEVER 0xFFFFFFFF

uint16_t cart[CARTRIDGE_WORDS];
uint16_t ram[RAM_WORDS];
uint8_t z80_ram[Z80_RAM_BYTES];

io_port gamepad_1;
io_port gamepad_2;

int headless = 0;
int z80_enabled = 1;

#ifndef MIN
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#endif

#define SMD_HEADER_SIZE 512
#define SMD_MAGIC1 0x03
#define SMD_MAGIC2 0xAA
#define SMD_MAGIC3 0xBB
#define SMD_BLOCK_SIZE 0x4000

int load_smd_rom(long filesize, FILE * f)
{
	uint8_t block[SMD_BLOCK_SIZE];
	filesize -= SMD_HEADER_SIZE;
	fseek(f, SMD_HEADER_SIZE, SEEK_SET);
	
	uint16_t * dst = cart;
	while (filesize > 0) {
		fread(block, 1, SMD_BLOCK_SIZE, f);
		for (uint8_t *low = block, *high = (block+SMD_BLOCK_SIZE/2), *end = block+SMD_BLOCK_SIZE; high < end; high++, low++) {
			*(dst++) = *high << 8 | *low;
		}
		filesize -= SMD_BLOCK_SIZE;
	}
	return 1;
}

int load_rom(char * filename)
{
	uint8_t header[10];
	FILE * f = fopen(filename, "rb");
	if (!f) {
		return 0;
	}
	fread(header, 1, sizeof(header), f);
	fseek(f, 0, SEEK_END);
	long filesize = ftell(f);
	if (filesize/2 > CARTRIDGE_WORDS) {
		//carts bigger than 4MB not currently supported
		filesize = CARTRIDGE_WORDS*2;
	}
	fseek(f, 0, SEEK_SET);
	if (header[1] == SMD_MAGIC1 && header[8] == SMD_MAGIC2 && header[9] == SMD_MAGIC3) {
		int i;
		for (i = 3; i < 8; i++) {
			if (header[i] != 0) {
				break;
			}
		}
		if (i == 8) {
			if (header[2]) {
				fprintf(stderr, "%s is a split SMD ROM which is not currently supported", filename);
				exit(1);
			}
			return load_smd_rom(filesize, f);
		}
	}
	fread(cart, 2, filesize/2, f);
	fclose(f);
	for(unsigned short * cur = cart; cur - cart < (filesize/2); ++cur)
	{
		*cur = (*cur >> 8) | (*cur << 8);
	}
	//TODO: Mirror ROM
	return 1;
}

uint16_t read_dma_value(uint32_t address)
{
	//addresses here are word addresses (i.e. bit 0 corresponds to A1), so no need to do div by 2
	if (address < 0x200000) {
		return cart[address];
	} else if(address >= 0x700000) {
		return ram[address & 0x7FFF];
	}
	//TODO: Figure out what happens when you try to DMA from weird adresses like IO or banked Z80 area
	return 0;
}

#define VINT_CYCLE ((MCLKS_LINE * 226)/MCLKS_PER_68K)
#define ZVINT_CYCLE ((MCLKS_LINE * 226)/MCLKS_PER_Z80)

void adjust_int_cycle(m68k_context * context, vdp_context * v_context)
{
	if (!(v_context->regs[REG_MODE_2] & 0x20 && ((context->status & 0x7) < 6)) || context->current_cycle >= VINT_CYCLE) {
		context->int_cycle = CYCLE_NEVER;
		context->target_cycle = context->sync_cycle;
	} else if (context->int_cycle > VINT_CYCLE) {
		context->int_cycle = VINT_CYCLE;
		context->int_num = 6;
		if (context->int_cycle < context->sync_cycle) {
			context->target_cycle = context->int_cycle;
		}
	}
}

int break_on_sync = 0;

uint8_t reset = 1;
uint8_t need_reset = 0;
uint8_t busreq = 0;
uint8_t busack = 0;
uint32_t busack_cycle = CYCLE_NEVER;
uint8_t new_busack = 0;
//#define DO_DEBUG_PRINT
#ifdef DO_DEBUG_PRINT
#define dprintf printf
#define dputs puts
#else
#define dprintf
#define dputs
#endif

void sync_z80(z80_context * z_context, uint32_t mclks)
{
	if (z80_enabled && !reset && !busreq) {
		if (need_reset) {
			z80_reset(z_context);
			need_reset = 0;
		}
		z_context->sync_cycle = mclks / MCLKS_PER_Z80;
		while (z_context->current_cycle < z_context->sync_cycle) {
			if (z_context->iff1 && z_context->current_cycle < ZVINT_CYCLE) {
				z_context->int_cycle = ZVINT_CYCLE;
			}
			z_context->target_cycle = z_context->sync_cycle < z_context->int_cycle ? z_context->sync_cycle : z_context->int_cycle;
			dprintf("Running Z80 from cycle %d to cycle %d. Native PC: %p\n", z_context->current_cycle, z_context->sync_cycle, z_context->native_pc);
			z80_run(z_context);
			dprintf("Z80 ran to cycle %d\n", z_context->current_cycle);
		}
	} else {
		z_context->current_cycle = mclks / MCLKS_PER_Z80;
	}
}

m68k_context * sync_components(m68k_context * context, uint32_t address)
{
	//TODO: Handle sync targets smaller than a single frame
	genesis_context * gen = context->system;
	vdp_context * v_context = gen->vdp;
	z80_context * z_context = gen->z80;
	uint32_t mclks = context->current_cycle * MCLKS_PER_68K;
	sync_z80(z_context, mclks);
	if (mclks >= MCLKS_PER_FRAME) {
		ym_run(gen->ym, context->current_cycle);
		gen->ym->current_cycle -= MCLKS_PER_FRAME/MCLKS_PER_68K;
		//printf("reached frame end | 68K Cycles: %d, MCLK Cycles: %d\n", context->current_cycle, mclks);
		vdp_run_context(v_context, MCLKS_PER_FRAME);
		if (!headless) {
			break_on_sync |= wait_render_frame(v_context);
		}
		mclks -= MCLKS_PER_FRAME;
		vdp_adjust_cycles(v_context, MCLKS_PER_FRAME);
		io_adjust_cycles(&gamepad_1, context->current_cycle, MCLKS_PER_FRAME/MCLKS_PER_68K);
		io_adjust_cycles(&gamepad_2, context->current_cycle, MCLKS_PER_FRAME/MCLKS_PER_68K);
		context->current_cycle -= MCLKS_PER_FRAME/MCLKS_PER_68K;
		if (z_context->current_cycle >= MCLKS_PER_FRAME/MCLKS_PER_Z80) {
			z_context->current_cycle -= MCLKS_PER_FRAME/MCLKS_PER_Z80;
		} else {
			z_context->current_cycle = 0;
		}
		if (mclks) {
			vdp_run_context(v_context, mclks);
		}
	} else {
		//printf("running VDP for %d cycles\n", mclks - v_context->cycles);
		vdp_run_context(v_context, mclks);
	}
	adjust_int_cycle(context, v_context);
	if (break_on_sync && address) {
		break_on_sync = 0;
		debugger(context, address);
	}
	return context;
}

m68k_context * vdp_port_write(uint32_t vdp_port, m68k_context * context, uint16_t value)
{
	//printf("vdp_port write: %X, value: %X, cycle: %d\n", vdp_port, value, context->current_cycle);
	sync_components(context, 0);
	vdp_context * v_context = context->video_context;
	if (vdp_port < 0x10) {
		int blocked;
		if (vdp_port < 4) {
			while (vdp_data_port_write(v_context, value) < 0) {
				while(v_context->flags & FLAG_DMA_RUN) {
					vdp_run_dma_done(v_context, MCLKS_PER_FRAME);
					if (v_context->cycles >= MCLKS_PER_FRAME) {
						if (!headless) {
							wait_render_frame(v_context);
						}
						vdp_adjust_cycles(v_context, MCLKS_PER_FRAME);
						io_adjust_cycles(&gamepad_1, v_context->cycles/MCLKS_PER_68K, MCLKS_PER_FRAME/MCLKS_PER_68K);
						io_adjust_cycles(&gamepad_2, v_context->cycles/MCLKS_PER_68K, MCLKS_PER_FRAME/MCLKS_PER_68K);
					}
				}
				context->current_cycle = v_context->cycles / MCLKS_PER_68K;
			}
		} else if(vdp_port < 8) {
			blocked = vdp_control_port_write(v_context, value);
			if (blocked) {
				while (blocked) {
					while(v_context->flags & FLAG_DMA_RUN) {
						vdp_run_dma_done(v_context, MCLKS_PER_FRAME);
						if (v_context->cycles >= MCLKS_PER_FRAME) {
							if (!headless) {
								wait_render_frame(v_context);
							}
							vdp_adjust_cycles(v_context, MCLKS_PER_FRAME);
							io_adjust_cycles(&gamepad_1, v_context->cycles/MCLKS_PER_68K, MCLKS_PER_FRAME/MCLKS_PER_68K);
							io_adjust_cycles(&gamepad_2, v_context->cycles/MCLKS_PER_68K, MCLKS_PER_FRAME/MCLKS_PER_68K);
						}
					}
					if (blocked < 0) {
						blocked = vdp_control_port_write(v_context, value);
					} else {
						blocked = 0;
					}
				}
				context->current_cycle = v_context->cycles / MCLKS_PER_68K;
			} else {
				adjust_int_cycle(context, v_context);
			}
		} else {
			printf("Illegal write to HV Counter port %X\n", vdp_port);
			exit(1);
		}
		context->current_cycle = v_context->cycles/MCLKS_PER_68K;
	} else if (vdp_port < 0x18) {
		//TODO: Implement PSG
	} else {
		//TODO: Implement undocumented test register(s)
	}
	return context;
}

m68k_context * vdp_port_read(uint32_t vdp_port, m68k_context * context)
{
	sync_components(context, 0);
	vdp_context * v_context = context->video_context;
	if (vdp_port < 0x10) {
		if (vdp_port < 4) {
			context->value = vdp_data_port_read(v_context);
		} else if(vdp_port < 8) {
			context->value = vdp_control_port_read(v_context);
		} else {
			context->value = vdp_hv_counter_read(v_context);
			//printf("HV Counter: %X at cycle %d\n", context->value, v_context->cycles);
		}
		context->current_cycle = v_context->cycles/MCLKS_PER_68K;
	} else {
		printf("Illegal read from PSG or test register port %X\n", vdp_port);
		exit(1);
	}
	return context;
}

#define TH 0x40
#define TH_TIMEOUT 8000

void io_adjust_cycles(io_port * pad, uint32_t current_cycle, uint32_t deduction)
{
	/*uint8_t control = pad->control | 0x80;
	uint8_t th = control & pad->output;
	if (pad->input[GAMEPAD_TH0] || pad->input[GAMEPAD_TH1]) {
		printf("adjust_cycles | control: %X, TH: %X, GAMEPAD_TH0: %X, GAMEPAD_TH1: %X, TH Counter: %d, Timeout: %d, Cycle: %d\n", control, th, pad->input[GAMEPAD_TH0], pad->input[GAMEPAD_TH1], pad->th_counter,pad->timeout_cycle, current_cycle);
	}*/
	if (current_cycle >= pad->timeout_cycle) {
		pad->th_counter = 0;
	} else {
		pad->timeout_cycle -= deduction;
	}
	if (busack_cycle < CYCLE_NEVER && current_cycle < busack_cycle) {
		busack_cycle -= deduction;
	}
}

void io_data_write(io_port * pad, m68k_context * context, uint8_t value)
{
	if (pad->control & TH) {
		//check if TH has changed
		if ((pad->output & TH) ^ (value & TH)) {
			if (context->current_cycle >= pad->timeout_cycle) {
				pad->th_counter = 0;
			}
			if (!(value & TH)) {
				pad->th_counter++;
			}
			pad->timeout_cycle = context->current_cycle + TH_TIMEOUT;
		}
	}
	pad->output = value;
}

void io_data_read(io_port * pad, m68k_context * context)
{
	uint8_t control = pad->control | 0x80;
	uint8_t th = control & pad->output;
	uint8_t input;
	if (context->current_cycle >= pad->timeout_cycle) {
		pad->th_counter = 0;
	}
	/*if (pad->input[GAMEPAD_TH0] || pad->input[GAMEPAD_TH1]) {
		printf("io_data_read | control: %X, TH: %X, GAMEPAD_TH0: %X, GAMEPAD_TH1: %X, TH Counter: %d, Timeout: %d, Cycle: %d\n", control, th, pad->input[GAMEPAD_TH0], pad->input[GAMEPAD_TH1], pad->th_counter,pad->timeout_cycle, context->current_cycle);
	}*/
	if (th) {
		if (pad->th_counter == 3) {
			input = pad->input[GAMEPAD_EXTRA];
		} else {
			input = pad->input[GAMEPAD_TH1];
		}
	} else {
		if (pad->th_counter == 3) {
			input = pad->input[GAMEPAD_TH0] | 0xF;
		} else if(pad->th_counter == 4) {
			input = pad->input[GAMEPAD_TH0]  & 0x30;
		} else {
			input = pad->input[GAMEPAD_TH0] | 0xC;
		}
	}
	context->value = ((~input) & (~control)) | (pad->output & control);
	/*if (pad->input[GAMEPAD_TH0] || pad->input[GAMEPAD_TH1]) {
		printf ("value: %X\n", context->value);
	}*/
}

uint32_t zram_counter = 0;
#define Z80_ACK_DELAY 3
#define Z80_BUSY_DELAY 2//TODO: Find the actual value for this
#define Z80_REQ_BUSY 1
#define Z80_REQ_ACK 0
#define Z80_RES_BUSACK reset

m68k_context * io_write(uint32_t location, m68k_context * context, uint8_t value)
{
	genesis_context * gen = context->system;
	if (location < 0x10000) {
		if (busack_cycle > context->current_cycle) {
			busack = new_busack;
			busack_cycle = CYCLE_NEVER;
		}
		if (!(busack || reset)) {
			location &= 0x7FFF;
			if (location < 0x4000) {
				z80_ram[location & 0x1FFF] = value;
				z80_handle_code_write(location & 0x1FFF, gen->z80);
			} else if (location < 0x6000) {
				ym_run(gen->ym, context->current_cycle);
				if (location & 1) {
					ym_data_write(gen->ym, value);
				} else if(location & 2) {
					ym_address_write_part2(gen->ym, value);
				} else {
					ym_address_write_part1(gen->ym, value);
				}
			}
		}
	} else {
		location &= 0x1FFF;
		if (location < 0x100) {
			switch(location/2)
			{
			case 0x1:
				io_data_write(&gamepad_1, context, value);
				break;
			case 0x2:
				io_data_write(&gamepad_2, context, value);
				break;
			case 0x3://PORT C Data
				break;
			case 0x4:
				gamepad_1.control = value;
				break;
			case 0x5:
				gamepad_2.control = value;
				break;
			}
		} else {
			if (location == 0x1100) {
				sync_z80(gen->z80, context->current_cycle * MCLKS_PER_68K);
				if (busack_cycle > context->current_cycle) {
					busack = new_busack;
					busack_cycle = CYCLE_NEVER;
				}
				if (value & 1) {
					dputs("bus requesting Z80");
					busreq = 1;
					if(!reset) {
						busack_cycle = ((gen->z80->current_cycle + Z80_ACK_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;//context->current_cycle + Z80_ACK_DELAY;
						new_busack = Z80_REQ_ACK;
					}
				} else {
					if (busreq) {
						dputs("releasing z80 bus");
						#ifdef DO_DEBUG_PRINT
						char fname[20];
						sprintf(fname, "zram-%d", zram_counter++);
						FILE * f = fopen(fname, "wb");
						fwrite(z80_ram, 1, sizeof(z80_ram), f);
						fclose(f);
						#endif
						//TODO: Add necessary delay between release of busreq and resumption of execution
					}
					busreq = 0;
					//busack_cycle = CYCLE_NEVER;
					//busack = Z80_REQ_BUSY;
					busack_cycle = ((gen->z80->current_cycle + Z80_BUSY_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;
					new_busack = Z80_REQ_BUSY;
				}
			} else if (location == 0x1200) {
				sync_z80(gen->z80, context->current_cycle * MCLKS_PER_68K);
				if (value & 1) {
					if (reset && busreq) {
						new_busack = 0;
						busack_cycle = ((gen->z80->current_cycle + Z80_ACK_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;//context->current_cycle + Z80_ACK_DELAY;
					}
					//TODO: Deal with the scenario in which reset is not asserted long enough
					if (reset) {
						need_reset = 1;
						//TODO: Add necessary delay between release of reset and start of execution
						gen->z80->current_cycle = (context->current_cycle * MCLKS_PER_68K) / MCLKS_PER_Z80;
					}
					reset = 0;
				} else {
					reset = 1;
				}
			}
		}
	}
	return context;
}

m68k_context * io_write_w(uint32_t location, m68k_context * context, uint16_t value)
{
	genesis_context * gen = context->system;
	if (location < 0x10000) {
		if (busack_cycle > context->current_cycle) {
			busack = new_busack;
			busack_cycle = CYCLE_NEVER;
		}
		if (!(busack || reset)) {
			location &= 0x7FFF;
			if (location < 0x4000) {
				z80_ram[location & 0x1FFE] = value >> 8;
				z80_handle_code_write(location & 0x1FFE, gen->z80);
			} else if (location < 0x6000) {
				ym_run(gen->ym, context->current_cycle);
				if (location & 1) {
					ym_data_write(gen->ym, value >> 8);
				} else if(location & 2) {
					ym_address_write_part2(gen->ym, value >> 8);
				} else {
					ym_address_write_part1(gen->ym, value >> 8);
				}
			}
		}
	} else {
		location &= 0x1FFF;
		if (location < 0x100) {
			switch(location/2)
			{
			case 0x1:
				io_data_write(&gamepad_1, context, value);
				break;
			case 0x2:
				io_data_write(&gamepad_2, context, value);
				break;
			case 0x3://PORT C Data
				break;
			case 0x4:
				gamepad_1.control = value;
				break;
			case 0x5:
				gamepad_2.control = value;
				break;
			}
		} else {
			//printf("IO Write of %X to %X @ %d\n", value, location, context->current_cycle);
			if (location == 0x1100) {
				sync_z80(gen->z80, context->current_cycle * MCLKS_PER_68K);
				if (busack_cycle > context->current_cycle) {
					busack = new_busack;
					busack_cycle = CYCLE_NEVER;
				}
				if (value & 0x100) {
					dprintf("bus requesting Z80 @ %d\n", (context->current_cycle * MCLKS_PER_68K) / MCLKS_PER_Z80);
					busreq = 1;
					if(!reset) {
						busack_cycle = ((gen->z80->current_cycle + Z80_ACK_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;//context->current_cycle + Z80_ACK_DELAY;
						new_busack = Z80_REQ_ACK;
					}
				} else {
					if (busreq) {
						dprintf("releasing Z80 bus @ %d\n", (context->current_cycle * MCLKS_PER_68K) / MCLKS_PER_Z80);
						#ifdef DO_DEBUG_PRINT
						char fname[20];
						sprintf(fname, "zram-%d", zram_counter++);
						FILE * f = fopen(fname, "wb");
						fwrite(z80_ram, 1, sizeof(z80_ram), f);
						fclose(f);
						#endif
						//TODO: Add necessary delay between release of busreq and resumption of execution
					}
					busreq = 0;
					//busack_cycle = CYCLE_NEVER;
					//busack = Z80_REQ_BUSY;
					busack_cycle = ((gen->z80->current_cycle + Z80_BUSY_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;
					new_busack = Z80_REQ_BUSY;
				}
			} else if (location == 0x1200) {
				sync_z80(gen->z80, context->current_cycle * MCLKS_PER_68K);
				if (value & 0x100) {
					if (reset && busreq) {
						new_busack = 0;
						busack_cycle = ((gen->z80->current_cycle + Z80_ACK_DELAY) * MCLKS_PER_Z80) / MCLKS_PER_68K;//context->current_cycle + Z80_ACK_DELAY;
					}
					//TODO: Deal with the scenario in which reset is not asserted long enough
					if (reset) {
						need_reset = 1;
						//TODO: Add necessary delay between release of reset and start of execution
					}
					reset = 0;
				} else {
					reset = 1;
				}
			}
		}
	}
	return context;
}

#define USA 0x80
#define JAP 0x00
#define EUR 0xC0
#define NO_DISK 0x20
uint8_t version_reg = NO_DISK | USA;

m68k_context * io_read(uint32_t location, m68k_context * context)
{
	genesis_context *gen = context->system;
	if (location < 0x10000) {
		if (busack_cycle > context->current_cycle) {
			busack = new_busack;
			busack_cycle = CYCLE_NEVER;
		}
		if (!(busack==Z80_REQ_BUSY || reset)) {
			location &= 0x7FFF;
			if (location < 0x4000) {
				context->value = z80_ram[location & 0x1FFF];
			} else if (location < 0x6000) {
				ym_run(gen->ym, context->current_cycle);
				context->value = ym_read_status(gen->ym);
			} else {
				context->value = 0xFF;
			}
		} else {
			context->value = 0xFF;
		}
	} else {
		location &= 0x1FFF;
		if (location < 0x100) {
			switch(location/2)
			{
			case 0x0:
				//version bits should be 0 for now since we're not emulating TMSS
				//Not sure about the other bits
				context->value = version_reg;
				break;
			case 0x1:
				io_data_read(&gamepad_1, context);
				break;
			case 0x2:
				io_data_read(&gamepad_2, context);
				break;
			case 0x3://PORT C Data
				break;
			case 0x4:
				context->value = gamepad_1.control;
				break;
			case 0x5:
				context->value = gamepad_2.control;
				break;
			}
		} else {
			if (location == 0x1100) {
				if (busack_cycle > context->current_cycle) {
					busack = new_busack;
					busack_cycle = CYCLE_NEVER;
				}
				context->value = Z80_RES_BUSACK || busack;
				//printf("Byte read of BUSREQ returned %d @ %d (reset: %d, busack: %d)\n", context->value, context->current_cycle, reset, busack);
			} else if (location == 0x1200) {
				context->value = !reset;
			} else {
				printf("Byte read of unknown IO location: %X\n", location);
			}
		}
	}
	return context;
}

m68k_context * io_read_w(uint32_t location, m68k_context * context)
{
	genesis_context * gen = context->system;
	if (location < 0x10000) {
		if (busack_cycle > context->current_cycle) {
			busack = new_busack;
			busack_cycle = CYCLE_NEVER;
		}
		if (!(busack==Z80_REQ_BUSY || reset)) {
			location &= 0x7FFF;
			uint16_t value;
			if (location < 0x4000) {
				value = z80_ram[location & 0x1FFE];
			} else if (location < 0x6000) {
				ym_run(gen->ym, context->current_cycle);
				value = ym_read_status(gen->ym);	
			} else {
				value = 0xFF;
			}
			context->value = value | (value << 8);
		} else {
			context->value = 0xFFFF;
		}
	} else {
		location &= 0x1FFF;
		if (location < 0x100) {
			switch(location/2)
			{
			case 0x0:
				//version bits should be 0 for now since we're not emulating TMSS
				//Not sure about the other bits
				context->value = 0;
				break;
			case 0x1:
				io_data_read(&gamepad_1, context);
				break;
			case 0x2:
				io_data_read(&gamepad_2, context);
				break;
			case 0x3://PORT C Data
				break;
			case 0x4:
				context->value = gamepad_1.control;
				break;
			case 0x5:
				context->value = gamepad_2.control;
				break;
			case 0x6:
				//PORT C Control
				context->value = 0;
				break;
			}
			context->value = context->value | (context->value << 8);
			//printf("Word read to %X returned %d\n", location, context->value);
		} else {
			if (location == 0x1100) {
				if (busack_cycle > context->current_cycle) {
					busack = new_busack;
					busack_cycle = CYCLE_NEVER;
				}
				context->value = (Z80_RES_BUSACK || busack) << 8;
				//printf("Word read of BUSREQ returned %d\n", context->value);
			} else if (location == 0x1200) {
				context->value = (!reset) << 8;
			} else {
				printf("Word read of unknown IO location: %X\n", location);
			}
		}
	}
	return context;
}

z80_context * z80_write_ym(uint16_t location, z80_context * context, uint8_t value)
{
	genesis_context * gen = context->system;
	ym_run(gen->ym, (context->current_cycle * MCLKS_PER_Z80) / MCLKS_PER_68K);
	if (location & 1) {
		ym_data_write(gen->ym, value);
	} else if (location & 2) {
		ym_address_write_part2(gen->ym, value);
	} else {
		ym_address_write_part1(gen->ym, value);
	}
	return context;
}

uint8_t z80_read_ym(uint16_t location, z80_context * context)
{
	genesis_context * gen = context->system;
	ym_run(gen->ym, (context->current_cycle * MCLKS_PER_Z80) / MCLKS_PER_68K);
	return ym_read_status(gen->ym);
}

typedef struct bp_def {
	struct bp_def * next;
	uint32_t address;
	uint32_t index;
} bp_def;

bp_def * breakpoints = NULL;
uint32_t bp_index = 0;

bp_def ** find_breakpoint(bp_def ** cur, uint32_t address)
{
	while (*cur) {
		if ((*cur)->address == address) {
			break;
		}
		cur = &((*cur)->next);
	}
	return cur;
}

bp_def ** find_breakpoint_idx(bp_def ** cur, uint32_t index)
{
	while (*cur) {
		if ((*cur)->index == index) {
			break;
		}
		cur = &((*cur)->next);
	}
	return cur;
}

char * find_param(char * buf)
{
	for (; *buf; buf++) {
		if (*buf == ' ') {
			if (*(buf+1)) {
				return buf+1;
			}
		}
	}
	return NULL;
}

void strip_nl(char * buf)
{
	for(; *buf; buf++) {
		if (*buf == '\n') {
			*buf = 0;
			return;
		}
	}
}

m68k_context * debugger(m68k_context * context, uint32_t address)
{
	static char last_cmd[1024];
	char input_buf[1024];
	static uint32_t branch_t;
	static uint32_t branch_f;
	m68kinst inst;
	//probably not necessary, but let's play it safe
	address &= 0xFFFFFF;
	if (address == branch_t) {
		bp_def ** f_bp = find_breakpoint(&breakpoints, branch_f);
		if (!*f_bp) {
			remove_breakpoint(context, branch_f);
		}
		branch_t = branch_f = 0;
	} else if(address == branch_f) {
		bp_def ** t_bp = find_breakpoint(&breakpoints, branch_t);
		if (!*t_bp) {
			remove_breakpoint(context, branch_t);
		}
		branch_t = branch_f = 0;
	}
	//Check if this is a user set breakpoint, or just a temporary one
	bp_def ** this_bp = find_breakpoint(&breakpoints, address);
	if (*this_bp) {
		printf("Breakpoint %d hit\n", (*this_bp)->index);
	} else {
		remove_breakpoint(context, address);
	}
	uint16_t * pc;
	if (address < 0x400000) {
		pc = cart + address/2;
	} else if(address > 0xE00000) {
		pc = ram + (address & 0xFFFF)/2;
	} else {
		fprintf(stderr, "Entered debugger at address %X\n", address);
		exit(1);
	}
	uint16_t * after_pc = m68k_decode(pc, &inst, address);
	m68k_disasm(&inst, input_buf);
	printf("%X: %s\n", address, input_buf);
	uint32_t after = address + (after_pc-pc)*2;
	int debugging = 1;
	while (debugging) {
		fputs(">", stdout);
		if (!fgets(input_buf, sizeof(input_buf), stdin)) {
			fputs("fgets failed", stderr);
			break;
		}
		strip_nl(input_buf);
		//hitting enter repeats last command
		if (input_buf[0]) {
			strcpy(last_cmd, input_buf);
		} else {
			strcpy(input_buf, last_cmd);
		}
		char * param;
		char format[8];
		uint32_t value;
		bp_def * new_bp;
		switch(input_buf[0])
		{
			case 'c':
				puts("Continuing");
				debugging = 0;
				break;
			case 'b':
				param = find_param(input_buf);
				if (!param) {
					fputs("b command requires a parameter\n", stderr);
					break;
				}
				value = strtol(param, NULL, 16);
				insert_breakpoint(context, value, (uint8_t *)debugger);
				new_bp = malloc(sizeof(bp_def));
				new_bp->next = breakpoints;
				new_bp->address = value;
				new_bp->index = bp_index++;
				breakpoints = new_bp;
				printf("Breakpoint %d set at %X\n", new_bp->index, value);
				break;
			case 'a':
				param = find_param(input_buf);
				if (!param) {
					fputs("a command requires a parameter\n", stderr);
					break;
				}
				value = strtol(param, NULL, 16);
				insert_breakpoint(context, value, (uint8_t *)debugger);
				debugging = 0;
				break;
			case 'd':
				param = find_param(input_buf);
				if (!param) {
					fputs("b command requires a parameter\n", stderr);
					break;
				}
				value = atoi(param);
				this_bp = find_breakpoint_idx(&breakpoints, value);
				if (!*this_bp) {
					fprintf(stderr, "Breakpoint %d does not exist\n", value);
					break;
				}
				new_bp = *this_bp;
				*this_bp = (*this_bp)->next;
				free(new_bp);
				break;
			case 'p':
				strcpy(format, "%s: %d\n");
				if (input_buf[1] == '/') {
					switch (input_buf[2])
					{
					case 'x':
					case 'X':
					case 'd':
					case 'c':
						format[5] = input_buf[2];
						break;
					default:
						fprintf(stderr, "Unrecognized format character: %c\n", input_buf[2]);
					}
				}
				param = find_param(input_buf);
				if (!param) {
					fputs("p command requires a parameter\n", stderr);
					break;
				}
				if (param[0] == 'd' && param[1] >= '0' && param[1] <= '7') {
					value = context->dregs[param[1]-'0'];
				} else if (param[0] == 'a' && param[1] >= '0' && param[1] <= '7') {
					value = context->aregs[param[1]-'0'];
				} else if (param[0] == 'S' && param[1] == 'R') {
					value = (context->status << 8);
					for (int flag = 0; flag < 5; flag++) {
						value |= context->flags[flag] << (4-flag);
					}
				} else if(param[0] == 'c') {
					value = context->current_cycle;
				} else if (param[0] == '0' && param[1] == 'x') {
					uint32_t p_addr = strtol(param+2, NULL, 16);
					value = read_dma_value(p_addr/2);
				} else {
					fprintf(stderr, "Unrecognized parameter to p: %s\n", param);
					break;
				}
				printf(format, param, value);
				break;
			case 'n':
				//TODO: Deal with jmp, dbcc, rtr and rte
				if (inst.op == M68K_RTS) {
					after = (read_dma_value(context->aregs[7]/2) << 16) | read_dma_value(context->aregs[7]/2 + 1);
				} else if(inst.op == M68K_BCC && inst.extra.cond != COND_FALSE) {
					if (inst.extra.cond = COND_TRUE) {
						after = inst.address + 2 + inst.src.params.immed;
					} else {
						branch_f = after;
						branch_t = inst.address + 2 + inst.src.params.immed;
						insert_breakpoint(context, branch_t, (uint8_t *)debugger);
					}
				}
				insert_breakpoint(context, after, (uint8_t *)debugger);
				debugging = 0;
				break;
			case 'q':
				puts("Quitting");
				exit(0);
				break;
			default:
				fprintf(stderr, "Unrecognized debugger command %s\n", input_buf);
				break;
		}
	}
	return context;
}

void init_run_cpu(genesis_context * gen, int debug, FILE * address_log)
{
	m68k_context context;
	x86_68k_options opts;
	gen->m68k = &context;
	init_x86_68k_opts(&opts);
	opts.address_log = address_log;
	init_68k_context(&context, opts.native_code_map, &opts);
	
	context.video_context = gen->vdp;
	context.system = gen;
	//cartridge ROM
	context.mem_pointers[0] = cart;
	context.target_cycle = context.sync_cycle = MCLKS_PER_FRAME/MCLKS_PER_68K;
	//work RAM
	context.mem_pointers[1] = ram;
	uint32_t address;
	/*address = cart[0x68/2] << 16 | cart[0x6A/2];
	translate_m68k_stream(address, &context);
	address = cart[0x70/2] << 16 | cart[0x72/2];
	translate_m68k_stream(address, &context);
	address = cart[0x78/2] << 16 | cart[0x7A/2];
	translate_m68k_stream(address, &context);*/
	address = cart[2] << 16 | cart[3];
	translate_m68k_stream(address, &context);
	if (debug) {
		insert_breakpoint(&context, address, (uint8_t *)debugger);
	}
	m68k_reset(&context);
}

int main(int argc, char ** argv)
{
	if (argc < 2) {
		fputs("Usage: blastem FILENAME\n", stderr);
		return 1;
	}
	if(!load_rom(argv[1])) {
		fprintf(stderr, "Failed to open %s for reading\n", argv[1]);
		return 1;
	}
	int width = -1;
	int height = -1;
	int debug = 0;
	FILE *address_log = NULL;
	for (int i = 2; i < argc; i++) {
		if (argv[i][0] == '-') {
			switch(argv[i][1]) {
			case 'd':
				debug = 1;
				break;
			case 'l':
				address_log = fopen("address.log", "w");
				break;
			case 'v':
				headless = 1;
				break;
			case 'n':
				z80_enabled = 0;
				break;
			default:
				fprintf(stderr, "Unrecognized switch %s\n", argv[i]);
				return 1;
			}
		} else if (width < 0) {
			width = atoi(argv[i]);
		} else if (height < 0) {
			height = atoi(argv[i]);
		}
	}
	width = width < 320 ? 320 : width;
	height = height < 240 ? (width/320) * 240 : height;
	if (!headless) {
		render_init(width, height);
	}
	vdp_context v_context;
	
	init_vdp_context(&v_context);
	
	ym2612_context y_context;
	ym_init(&y_context);
	
	z80_context z_context;
	x86_z80_options z_opts;
	init_x86_z80_opts(&z_opts);
	init_z80_context(&z_context, &z_opts);

	genesis_context gen;	

	z_context.system = &gen;
	z_context.mem_pointers[0] = z80_ram;
	z_context.sync_cycle = z_context.target_cycle = MCLKS_PER_FRAME/MCLKS_PER_Z80;
	z_context.int_cycle = CYCLE_NEVER;
	z_context.mem_pointers[1] = z_context.mem_pointers[2] = (uint8_t *)cart;
	
	gen.z80 = &z_context;
	gen.vdp = &v_context;
	gen.ym = &y_context;
	
	init_run_cpu(&gen, debug, address_log);
	return 0;
}