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Half assed, prefetch based open bus value emulation. Gets BlastEm up to 119/122 in VDP FIFO Testing
author Michael Pavone <pavone@retrodev.com>
date Sun, 24 Apr 2016 02:19:48 -0700
parents 34b811ea1e7c
children 2bc27415565b
comparison
equal deleted inserted replaced
980:928442068afe 981:902c53d9c16f
140 return *ptr; 140 return *ptr;
141 } 141 }
142 } 142 }
143 //TODO: Figure out what happens when you try to DMA from weird adresses like IO or banked Z80 area 143 //TODO: Figure out what happens when you try to DMA from weird adresses like IO or banked Z80 area
144 return 0; 144 return 0;
145 }
146
147 uint16_t get_open_bus_value()
148 {
149 return read_dma_value(genesis->m68k->last_prefetch_address/2);
145 } 150 }
146 151
147 void adjust_int_cycle(m68k_context * context, vdp_context * v_context) 152 void adjust_int_cycle(m68k_context * context, vdp_context * v_context)
148 { 153 {
149 //static int old_int_cycle = CYCLE_NEVER; 154 //static int old_int_cycle = CYCLE_NEVER;
703 value = 0xFF; 708 value = 0xFF;
704 } 709 }
705 } else { 710 } else {
706 if (location == 0x1100) { 711 if (location == 0x1100) {
707 value = z80_enabled ? !z80_get_busack(gen->z80, context->current_cycle) : !gen->z80->busack; 712 value = z80_enabled ? !z80_get_busack(gen->z80, context->current_cycle) : !gen->z80->busack;
708 //TODO: actual pre-fetch emulation 713 value |= (get_open_bus_value() >> 8) & 0xFE;
709 value |= 0x4E;
710 dprintf("Byte read of BUSREQ returned %d @ %d (reset: %d)\n", value, context->current_cycle, gen->z80->reset); 714 dprintf("Byte read of BUSREQ returned %d @ %d (reset: %d)\n", value, context->current_cycle, gen->z80->reset);
711 } else if (location == 0x1200) { 715 } else if (location == 0x1200) {
712 value = !gen->z80->reset; 716 value = !gen->z80->reset;
713 } else { 717 } else {
714 value = 0xFF; 718 value = 0xFF;
724 uint16_t value = io_read(location, context); 728 uint16_t value = io_read(location, context);
725 if (location < 0x10000 || (location & 0x1FFF) < 0x100) { 729 if (location < 0x10000 || (location & 0x1FFF) < 0x100) {
726 value = value | (value << 8); 730 value = value | (value << 8);
727 } else { 731 } else {
728 value <<= 8; 732 value <<= 8;
729 //TODO: actual pre-fetch emulation 733 value |= get_open_bus_value() & 0xFF;
730 value |= 0x73;
731 } 734 }
732 return value; 735 return value;
733 } 736 }
734 737
735 void * z80_write_ym(uint32_t location, void * vcontext, uint8_t value) 738 void * z80_write_ym(uint32_t location, void * vcontext, uint8_t value)