/*************************************************************************** machine.c Functions to emulate general aspects of the machine (RAM, ROM, interrupts, I/O ports) ***************************************************************************/ #include "driver.h" #include "M6809.h" int defender_bank; int bank_address; extern void williams_sh_w(int offset,int data); extern void Williams_Palette_w(int offset,int data); int video_counter; int Index; int Stargate_IntTable[] = {0,0xFF,0x00,0xff}; /* * int IntTable[] = {0,0x40,0xC0,0xff}; * int IntTable[] = {0,0x24,0x48,0x6c,0x90,0xB4,0xD8,0xff}; * int IntTable[] = {0,0x55,0xAA,0xff}; * * MUST be in this order to have the Back Zone not in the playfield * in Joust. */ int IntTable[] = {0xAA,0xff,0,0x55}; /* * int IntTable[] = {0x00,0x00,0x00,0x00}; * int IntTable[] = {0x00,0x10,0x20,0x30,0x40,0x50,0x60,0x70,0x80,0x90,0xa0,0xb0,0xc0,0xd0,0xe0,0xff}; * * Here is some test that I have done, This is for the value of 0xCB00 * It affect the color cycling and/or the speed of the game * 0xCB00 is the value of the video counter (6 hi bits) * IRQ is supposed to be at 4 ms interval. * I put IRQ 4 times by frame so we are supposed to have near 4 ms * * So, the value of CB00 normally pass all the values from 0 to 0xFC each * frame. * After trying many combination, I found that Stargate have to have * more time than the others games between IRQs, but will work if he see * only 00 and FF at $CB00. So I call IRQ just 2 times by frame. * If I do like the others, IRQ 4 time by frames, I need to boost the * CPU speed, but even pass 2 mhz, the game will freeze if he dont have * time to execute all he is supposed to before the next IRQ. * Same thing with Defender. This thing was observed even on the arcade * board. In defender, on the first wave try to catch more than 7 man, * stop your ship, press DOWN to drop the mens. You will see the * game slowdown. If you had the 10 men, it will freeze for a long * period of time. On the emulator, it crash if there is not enough * instructions executed before the video counter reached a certain * value. * But Robotron will not work if only 0 and FF pass at CB00, he want * more value.With only 0 and FF the color cycling do not work. * Joust is like Robotron, but, the values has to match the real * thing. What I mean is that normally the first IRQ is supposed * to be after the first Quarter of a screen refresh, the second * is supposed to appen at the middle of the screen... * So, the value at CB00 has to follow that rule. * In Joust, when a shape is erased, it is displayed at the new position * just at the next IRQ. So we have a blackout area in the screen. * If the value of CB00 are not synchronized with our computer, this * blackout zone can be in the middle of the screen. * Thats why the values in the table are 0xAA,0xff,0,0x55 and not * 0,0x55,0xAA,0xff. It seem to work fine. */ int Williams_Interrupt(void) { video_counter = IntTable[Index&0x03]; Index++; return INT_IRQ; } int Stargate_Interrupt(void) { video_counter = Stargate_IntTable[Index&0x03]; Index++; return INT_IRQ; } int Defender_Interrupt(void) { video_counter = Stargate_IntTable[Index&0x03]; Index++; /* * IRQ only if enabled (0x3C will it work all the time? or should * I check for a bit?) * I think I should check for 111 in bits 5-3 but it work anyway */ if (RAM[0x10000+0xc07] == 0x3C) return INT_IRQ; return INT_NONE; } int video_counter_r(int offset) { /* if (errorlog) fprintf(errorlog,"### Get Video counter %02X at %04X\n",video_counter,m6809_GetPC()); */ return video_counter; } /************** * */ int williams_init_machine(const char *gamename) { if(strcmp(gamename,"blaster") == 0){ /*So we do not have to copy the roms in RAM[] when bank switching On my system its much faster.*/ m6809_Flags = M6809_FAST_NONE; return 0; } if(strcmp(gamename,"defender") == 0){ /*So we do not have to copy the roms in RAM[] when bank switching*/ m6809_Flags = M6809_FAST_NONE; return 0; } /*The cpu will fetch its instructions directly in RAM[]*/ m6809_Flags = M6809_FAST_OP; return 0; } /* * For Joust */ int input_port_0_1(int offset) { if((RAM[0xc807] & 0x1C) == 0x1C) return input_port_1_r(0); else return input_port_0_r(0); } /* * For Blaster */ int blaster_input_port_0(int offset) { int i; int keys; keys = input_port_0_r(0); if(keys & 0x04) i = 0x00; else if(keys & 0x08) i = 0x80; else i = 0x40; if(keys&0x02) i += 0x00; else if(keys&0x01) i += 0x08; else i += 0x04; return i; } /* * Defender Read at C000-CFFF */ int defender_bank_r(int offset) { if(defender_bank == 0){ /* If bank = 0 then we are in the I/O */ if(offset == 0xc00) /* Buttons IN 0 */ return input_port_0_r(0); if(offset == 0xc04) /* Buttons IN 1 */ return input_port_1_r(0); if(offset == 0xc06) /* Buttons IN 2 */ return input_port_2_r(0); if(offset == 0x800) /* video counter */ return video_counter; /* Log * if (errorlog) * fprintf(errorlog,"-- Read %04X at %04X\n",0xC000+offset,m6809_GetPC()); * else = RAM */ return RAM[0x10000+offset]; } /* If not bank 0 then read RAM[] */ return RAM[bank_address+offset]; } /* * Defender Write at C000-CFFF */ void defender_bank_w(int offset,int data) { if (defender_bank == 0) { RAM[0x10000+offset] = data; /* WatchDog */ if (offset == 0x03FC) return; /* Palette */ if (offset < 0x10) Williams_Palette_w(offset,data); /* Sound */ if (offset == 0x0c02) williams_sh_w(offset,data); } } /* * Defender Select a bank * There is just data in bank 0 */ void defender_bank_select_w(int offset,int data) { if (data == 7) data = 4; /* more convenient for us */ if (defender_bank == data) return; defender_bank = data; bank_address = data*0x1000 + 0x10000; /*Address of the ROM */ } /* * Blaster bank select */ void blaster_bank_select_w(int offset,int data) { if (defender_bank == data) return; bank_address = data*0x4000 + 0x10000; /*Address of the ROM */ defender_bank = data; /* Banks are 0x4000 byte long from 0x10000 in RAM */ }