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Hardware multiplication and division on the SNES takes 8 machine cycles to complete.

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This commit is contained in:
Wilbert Pol 2009-12-30 18:47:21 +00:00
parent e277de3812
commit 2d26bc8efb
1 changed files with 41 additions and 25 deletions
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66
src/mame/machine/snes.c
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@ -36,6 +36,8 @@ static emu_timer *snes_scanline_timer;
static emu_timer *snes_hblank_timer;
static emu_timer *snes_nmi_timer;
static emu_timer *snes_hirq_timer;
static emu_timer *snes_div_timer;
static emu_timer *snes_mult_timer;
static UINT16 hblank_offset;
UINT16 snes_htmult; /* in 512 wide, we run HTOTAL double and halve it on latching */
UINT8 snes_has_addon_chip;
@ -176,7 +178,7 @@ static TIMER_CALLBACK( snes_scanline_tick )
timer_adjust_oneshot(snes_hirq_timer, video_screen_get_time_until_pos(machine->primary_screen, snes_ppu.beam.current_vert, pixel*snes_htmult), 0);
}
}
}
}
/* Start of VBlank */
if( snes_ppu.beam.current_vert == snes_ppu.beam.last_visible_line )
@ -294,6 +296,36 @@ static TIMER_CALLBACK( snes_hblank_tick )
}
static TIMER_CALLBACK(snes_div_callback)
{
UINT16 value, dividend, remainder;
dividend = remainder = 0;
value = (snes_ram[WRDIVH] << 8) + snes_ram[WRDIVL];
if( snes_ram[WRDVDD] > 0 )
{
dividend = value / snes_ram[WRDVDD];
remainder = value % snes_ram[WRDVDD];
}
else
{
dividend = 0xffff;
remainder = value;
}
snes_ram[RDDIVL] = dividend & 0xff;
snes_ram[RDDIVH] = (dividend >> 8) & 0xff;
snes_ram[RDMPYL] = remainder & 0xff;
snes_ram[RDMPYH] = (remainder >> 8) & 0xff;
}
static TIMER_CALLBACK(snes_mult_callback)
{
UINT32 c = snes_ram[WRMPYA] * snes_ram[WRMPYB];
snes_ram[RDMPYL] = c & 0xff;
snes_ram[RDMPYH] = (c >> 8) & 0xff;
}
/*************************************
Input Handlers
@ -1291,34 +1323,14 @@ WRITE8_HANDLER( snes_w_io )
case WRMPYA: /* Multiplier A */
break;
case WRMPYB: /* Multiplier B */
{
UINT32 c = snes_ram[WRMPYA] * data;
snes_ram[RDMPYL] = c & 0xff;
snes_ram[RDMPYH] = (c >> 8) & 0xff;
} break;
timer_adjust_oneshot(snes_mult_timer, cputag_clocks_to_attotime(space->machine, "maincpu", 8), 0);
break;
case WRDIVL: /* Dividend (low) */
case WRDIVH: /* Dividend (high) */
break;
case WRDVDD: /* Divisor */
{
UINT16 value, dividend, remainder;
dividend = remainder = 0;
value = (snes_ram[WRDIVH] << 8) + snes_ram[WRDIVL];
if( data > 0 )
{
dividend = value / data;
remainder = value % data;
}
else
{
dividend = 0xffff;
remainder = value;
}
snes_ram[RDDIVL] = dividend & 0xff;
snes_ram[RDDIVH] = (dividend >> 8) & 0xff;
snes_ram[RDMPYL] = remainder & 0xff;
snes_ram[RDMPYH] = (remainder >> 8) & 0xff;
} break;
timer_adjust_oneshot(snes_div_timer, cputag_clocks_to_attotime(space->machine, "maincpu", 8), 0);
break;
case HTIMEL: /* H-Count timer settings (low) */
case HTIMEH: /* H-Count timer settings (high) */
case VTIMEL: /* V-Count timer settings (low) */
@ -1983,6 +1995,10 @@ static void snes_init_timers(running_machine *machine)
timer_adjust_oneshot(snes_nmi_timer, attotime_never, 0);
snes_hirq_timer = timer_alloc(machine, snes_hirq_tick_callback, NULL);
timer_adjust_oneshot(snes_hirq_timer, attotime_never, 0);
snes_div_timer = timer_alloc(machine, snes_div_callback, NULL);
timer_adjust_oneshot(snes_div_timer, attotime_never, 0);
snes_mult_timer = timer_alloc(machine, snes_mult_callback, NULL);
timer_adjust_oneshot(snes_mult_timer, attotime_never, 0);
// SNES hcounter has a 0-339 range. hblank starts at counter 260.
// clayfighter sets an HIRQ at 260, apparently it wants it to be before hdma kicks off, so we'll delay 2 pixels.