diff --git a/Core/display.c b/Core/display.c index c664a56..2d4879b 100644 --- a/Core/display.c +++ b/Core/display.c @@ -250,6 +250,13 @@ void display_run(GB_gameboy_t *gb) */ unsigned char last_mode = gb->io_registers[GB_IO_STAT] & 3; + /* + STAT interrupt is implemented based on this finding: + http://board.byuu.org/phpbb3/viewtopic.php?p=25527#p25531 + */ + unsigned char previous_stat_interrupt_line = gb->stat_interrupt_line; + gb->stat_interrupt_line = false; + if (gb->display_cycles >= LCDC_PERIOD) { /* VBlank! */ gb->display_cycles -= LCDC_PERIOD; @@ -278,14 +285,10 @@ void display_run(GB_gameboy_t *gb) gb->io_registers[GB_IO_LY] = gb->display_cycles / 456; - bool previous_coincidence_flag = gb->io_registers[GB_IO_STAT] & 4; - gb->io_registers[GB_IO_STAT] &= ~4; if (gb->io_registers[GB_IO_LY] == gb->io_registers[GB_IO_LYC]) { gb->io_registers[GB_IO_STAT] |= 4; - if ((gb->io_registers[GB_IO_STAT] & 0x40) && !previous_coincidence_flag) { /* User requests an interrupt on coincidence*/ - gb->io_registers[GB_IO_IF] |= 2; - } + gb->stat_interrupt_line = true; } /* Todo: This behavior is seen in BGB and it fixes some ROMs with delicate timing, such as Hitman's 8bit. @@ -299,10 +302,10 @@ void display_run(GB_gameboy_t *gb) gb->effective_window_enabled = false; gb->effective_window_y = 0xFF; + if (gb->io_registers[GB_IO_STAT] & 16) { /* User requests an interrupt on VBlank*/ + gb->stat_interrupt_line = true; + } if (last_mode != 1) { - if (gb->io_registers[GB_IO_STAT] & 16) { /* User requests an interrupt on VBlank*/ - gb->io_registers[GB_IO_IF] |= 2; - } gb->io_registers[GB_IO_IF] |= 1; } @@ -328,7 +331,7 @@ void display_run(GB_gameboy_t *gb) } } - return; + goto updateSTAT; } // Todo: verify this window behavior. It is assumed from the expected behavior of 007 - The World Is Not Enough. @@ -338,16 +341,11 @@ void display_run(GB_gameboy_t *gb) if (gb->display_cycles % 456 < 80) { /* Mode 2 */ gb->io_registers[GB_IO_STAT] |= 2; /* Set mode to 2 */ - if (last_mode != 2) { - if (gb->io_registers[GB_IO_STAT] & 0x20) { /* User requests an interrupt on Mode 2 */ - gb->io_registers[GB_IO_IF] |= 2; - } - /* User requests an interrupt on LY=LYC*/ - if (gb->io_registers[GB_IO_STAT] & 64 && gb->io_registers[GB_IO_STAT] & 4) { - gb->io_registers[GB_IO_IF] |= 2; - } + if (gb->io_registers[GB_IO_STAT] & 0x20) { /* User requests an interrupt on Mode 2 */ + gb->stat_interrupt_line = true; } + /* See above comment about window behavior. */ if (gb->effective_window_enabled && gb->effective_window_y == 0xFF) { gb->effective_window_y = gb->io_registers[GB_IO_LY]; @@ -355,7 +353,7 @@ void display_run(GB_gameboy_t *gb) /* Todo: Figure out how the Gameboy handles in-line changes to SCX */ gb->line_x_bias = - (gb->io_registers[GB_IO_SCX] & 0x7); gb->previous_lcdc_x = gb->line_x_bias; - return; + goto updateSTAT; } signed short current_lcdc_x = ((gb->display_cycles % 456 - 80) & ~7) + gb->line_x_bias; @@ -372,19 +370,23 @@ void display_run(GB_gameboy_t *gb) if (gb->display_cycles % 456 < 80 + 172) { /* Mode 3 */ gb->io_registers[GB_IO_STAT] |= 3; /* Set mode to 3 */ - return; + goto updateSTAT; } /* if (gb->display_cycles % 456 < 80 + 172 + 204) */ { /* Mode 0*/ + if (gb->io_registers[GB_IO_STAT] & 8) { /* User requests an interrupt on Mode 0 */ + gb->stat_interrupt_line = true; + } if (last_mode != 0) { - if (gb->io_registers[GB_IO_STAT] & 8) { /* User requests an interrupt on Mode 0 */ - gb->io_registers[GB_IO_IF] |= 2; - } if (gb->hdma_on_hblank) { gb->hdma_on = true; gb->hdma_cycles = 0; } } - return; + } + +updateSTAT: + if (gb->stat_interrupt_line && !previous_stat_interrupt_line) { + gb->io_registers[GB_IO_IF] |= 2; } } diff --git a/Core/gb.h b/Core/gb.h index 1207e61..a1c9f15 100644 --- a/Core/gb.h +++ b/Core/gb.h @@ -6,7 +6,7 @@ #include #include "apu.h" -#define GB_STRUCT_VERSION 6 +#define GB_STRUCT_VERSION 7 enum { GB_REGISTER_AF, @@ -225,6 +225,7 @@ typedef struct GB_gameboy_s{ signed short line_x_bias; bool effective_window_enabled; unsigned char effective_window_y; + bool stat_interrupt_line; unsigned char bios[0x900]; bool bios_finished;