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More accurate emulation of the DMG-emulation-mode registers.

This commit is contained in:
Lior Halphon 2016-04-05 23:21:51 +03:00
parent cda6621dc2
commit 3e135a7c00
2 changed files with 14 additions and 6 deletions
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10
Core/gb.h
View File

@ -88,8 +88,11 @@ enum {
GB_IO_OBP1 = 0x49, // Object Palette 1 Data (R/W) - Non CGB Mode Only
GB_IO_WY = 0x4a, // Window Y Position (R/W)
GB_IO_WX = 0x4b, // Window X Position minus 7 (R/W)
/* Missing */
// Has some undocumented compatibility flags written at boot.
// Unfortunately it is not readable or writable after boot has finished, so research of this
// register is quite limited. The value written to this register, however, can be controlled
// in some cases.
GB_IO_DMG_EMULATION = 0x4c,
/* General CGB features */
GB_IO_KEY1 = 0x4d, // CGB Mode Only - Prepare Speed Switch
@ -117,7 +120,8 @@ enum {
GB_IO_OBPI = 0x6a, // CGB Mode Only - Sprite Palette Index
GB_IO_OBPD = 0x6b, // CGB Mode Only - Sprite Palette Data
GB_IO_DMG_EMULATION = 0x6c, // (FEh) Bit 0 (Read/Write) - CGB Mode Only
// 1 is written for DMG ROMs on a CGB. Does not appear to have an effect.
GB_IO_DMG_EMULATION_INDICATION = 0x6c, // (FEh) Bit 0 (Read/Write)
/* Missing */

10
Core/memory.c
View File

@ -100,6 +100,8 @@ static unsigned char read_high_memory(GB_gameboy_t *gb, unsigned short addr)
return gb->io_registers[GB_IO_TAC] | 0xF8;
case GB_IO_STAT:
return gb->io_registers[GB_IO_STAT] | 0x80;
case GB_IO_DMG_EMULATION_INDICATION:
return gb->io_registers[GB_IO_DMG_EMULATION_INDICATION] | 0xFE;
case GB_IO_JOYP:
case GB_IO_DIV:
case GB_IO_TIMA:
@ -155,7 +157,7 @@ static unsigned char read_high_memory(GB_gameboy_t *gb, unsigned short addr)
}
case GB_IO_KEY1:
if (!gb->is_cgb) {
if (!gb->cgb_mode) {
return 0xFF;
}
return (gb->io_registers[GB_IO_KEY1] & 0x7F) | (gb->cgb_double_speed? 0xFE : 0x7E);
@ -349,6 +351,7 @@ static void write_high_memory(GB_gameboy_t *gb, unsigned short addr, unsigned ch
case GB_IO_HDMA3:
case GB_IO_HDMA4:
case GB_IO_SB:
case GB_IO_DMG_EMULATION_INDICATION:
gb->io_registers[addr & 0xFF] = value;
return;
@ -382,8 +385,9 @@ static void write_high_memory(GB_gameboy_t *gb, unsigned short addr, unsigned ch
return;
case GB_IO_DMG_EMULATION:
// Todo: Can it be disabled? What about values other than 1?
gb->cgb_mode = false;
if (gb->is_cgb && !gb->bios_finished) {
gb->cgb_mode = value != 4; /* The real "contents" of this register aren't quite known yet. */
}
return;
case GB_IO_DMA: