RaySollium99/picodrive
1
0
Fork 0
mirror of https://github.com/RaySollium99/picodrive.git synced 2025-09-05 15:27:46 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

sound, improve ym2612 timers implementation

Browse source
This commit is contained in:
kub 2023-06-30 19:12:53 +00:00
parent 914525c3d5
commit 0e2e188e1e
2 changed files with 47 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

71
pico/memory.c
View file

@ -1041,7 +1041,7 @@ static int get_scanline(int is_from_z80)
if (is_from_z80) {
// ugh... compute by dividing cycles since frame start by cycles per line
// need some fractional resolution here, else there may be an extra line
int cycles_line = cycles_68k_to_z80(488 << 8); // cycles per line, as Q8
int cycles_line = cycles_68k_to_z80(488 << 8)+1; // cycles per line, as Q8
int cycles_z80 = (z80_cyclesLeft<0 ? Pico.t.z80c_aim:z80_cyclesDone())<<8;
int cycles = cycles_line * Pico.t.z80_scanline;
// approximation by multiplying with inverse
@ -1063,45 +1063,65 @@ static int get_scanline(int is_from_z80)
return Pico.m.scanline;
}
#define ym2612_update_status(xcycles) \
if (xcycles >= Pico.t.timer_a_next_oflow) \
ym2612.OPN.ST.status |= (ym2612.OPN.ST.mode >> 2) & 1; \
if (xcycles >= Pico.t.timer_b_next_oflow) \
ym2612.OPN.ST.status |= (ym2612.OPN.ST.mode >> 2) & 2
/* probably should not be in this file, but it's near related code here */
void ym2612_sync_timers(int z80_cycles, int mode_old, int mode_new)
{
int xcycles = z80_cycles << 8;
/* check for overflows */
if ((mode_old & 4) && xcycles >= Pico.t.timer_a_next_oflow)
ym2612.OPN.ST.status |= 1;
// update timer status
ym2612_update_status(xcycles);
if ((mode_old & 8) && xcycles >= Pico.t.timer_b_next_oflow)
ym2612.OPN.ST.status |= 2;
/* update timer a */
// update timer a
if (mode_old & 1)
while (xcycles > Pico.t.timer_a_next_oflow)
while (xcycles >= Pico.t.timer_a_next_oflow)
Pico.t.timer_a_next_oflow += Pico.t.timer_a_step;
if ((mode_old ^ mode_new) & 1) // turning on/off
// turning on/off
if ((mode_old ^ mode_new) & 1)
{
if (mode_old & 1)
Pico.t.timer_a_next_oflow = TIMER_NO_OFLOW;
else
Pico.t.timer_a_next_oflow = xcycles + Pico.t.timer_a_step;
else {
/* The internal tick of the YM2612 takes 144 clock cycles (with clock
* being OSC/7), or 67.2 z80 cycles. Timers are run once each tick.
* Starting a timer takes place at the next tick, so xcycles needs to be
* rounded up to that: t = next tick# = (xcycles / TICK_ZCYCLES) + 1
*/
unsigned t = ((xcycles * (((1<<20)/TIMER_A_TICK_ZCYCLES)+1))>>20) + 1;
Pico.t.timer_a_next_oflow = t*TIMER_A_TICK_ZCYCLES + Pico.t.timer_a_step;
}
}
if (mode_new & 1)
elprintf(EL_YMTIMER, "timer a upd to %i @ %i", Pico.t.timer_a_next_oflow>>8, z80_cycles);
/* update timer b */
// update timer b
if (mode_old & 2)
while (xcycles > Pico.t.timer_b_next_oflow)
while (xcycles >= Pico.t.timer_b_next_oflow)
Pico.t.timer_b_next_oflow += Pico.t.timer_b_step;
// turning on/off
if ((mode_old ^ mode_new) & 2)
{
if (mode_old & 2)
Pico.t.timer_b_next_oflow = TIMER_NO_OFLOW;
else
Pico.t.timer_b_next_oflow = xcycles + Pico.t.timer_b_step;
else {
/* timer b has a divider of 16 which runs in its own counter. It is not
* reset by loading timer b. The first run of timer b after loading is
* therefore shorter by up to 15 ticks.
*/
unsigned t = ((xcycles * (((1<<20)/TIMER_A_TICK_ZCYCLES)+1))>>20) + 1;
int step = Pico.t.timer_b_step - TIMER_A_TICK_ZCYCLES*(t&15);
Pico.t.timer_b_next_oflow = t*TIMER_A_TICK_ZCYCLES + step;
}
}
if (mode_new & 2)
elprintf(EL_YMTIMER, "timer b upd to %i @ %i", Pico.t.timer_b_next_oflow>>8, z80_cycles);
}
@ -1130,6 +1150,7 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
switch (addr)
{
// NB, OD2 A/V sync HACK: lower timer step by 1/4 z80 cycle (=64 in Q8)
case 0x24: // timer A High 8
case 0x25: { // timer A Low 2
int TAnew = (addr == 0x24) ? ((ym2612.OPN.ST.TA & 0x03)|(((int)d)<<2))
@ -1142,7 +1163,7 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
ym2612.OPN.ST.TA = TAnew;
//ym2612.OPN.ST.TAC = (1024-TAnew)*18;
//ym2612.OPN.ST.TAT = 0;
Pico.t.timer_a_step = TIMER_A_TICK_ZCYCLES * (1024 - TAnew);
Pico.t.timer_a_step = TIMER_A_TICK_ZCYCLES * (1024 - TAnew) - 64;
elprintf(EL_YMTIMER, "timer a set to %i, %i", 1024 - TAnew, Pico.t.timer_a_next_oflow>>8);
}
return 0;
@ -1155,7 +1176,7 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
ym2612.OPN.ST.TB = d;
//ym2612.OPN.ST.TBC = (256-d) * 288;
//ym2612.OPN.ST.TBT = 0;
Pico.t.timer_b_step = TIMER_B_TICK_ZCYCLES * (256 - d); // 262800
Pico.t.timer_b_step = TIMER_B_TICK_ZCYCLES * (256 - d) - 64;
elprintf(EL_YMTIMER, "timer b set to %i, %i", 256 - d, Pico.t.timer_b_next_oflow>>8);
}
return 0;
@ -1163,11 +1184,11 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
int old_mode = ym2612.OPN.ST.mode;
int cycles = is_from_z80 ? z80_cyclesDone() : z80_cycles_from_68k();
ym2612.OPN.ST.mode = d;
elprintf(EL_YMTIMER, "st mode %02x", d);
ym2612_sync_timers(cycles, old_mode, d);
ym2612.OPN.ST.mode = d;
/* reset Timer a flag */
if (d & 0x10)
ym2612.OPN.ST.status &= ~1;
@ -1213,17 +1234,11 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
}
#define ym2612_read_local() \
if (xcycles >= Pico.t.timer_a_next_oflow) \
ym2612.OPN.ST.status |= (ym2612.OPN.ST.mode >> 2) & 1; \
if (xcycles >= Pico.t.timer_b_next_oflow) \
ym2612.OPN.ST.status |= (ym2612.OPN.ST.mode >> 2) & 2
static u32 ym2612_read_local_z80(void)
{
int xcycles = z80_cyclesDone() << 8;
ym2612_read_local();
ym2612_update_status(xcycles);
elprintf(EL_YMTIMER, "timer z80 read %i, sched %i, %i @ %i|%i",
ym2612.OPN.ST.status, Pico.t.timer_a_next_oflow >> 8,
@ -1235,7 +1250,7 @@ static u32 ym2612_read_local_68k(void)
{
int xcycles = z80_cycles_from_68k() << 8;
ym2612_read_local();
ym2612_update_status(xcycles);
elprintf(EL_YMTIMER, "timer 68k read %i, sched %i, %i @ %i|%i",
ym2612.OPN.ST.status, Pico.t.timer_a_next_oflow >> 8,