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core z80, improve timing for bus request/grant timing from 68k

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kub 2024-03-14 23:15:16 +01:00
parent 8b0e2b4f9a
commit 71f9c68f5b
2 changed files with 14 additions and 6 deletions
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16
pico/memory.c
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@ -521,13 +521,19 @@ void NOINLINE ctl_write_z80busreq(u32 d)
{ {
if (d) if (d)
{ {
Pico.t.z80c_cnt = z80_cycles_from_68k() + 1; Pico.t.z80c_cnt = z80_cycles_from_68k() + (Pico.t.z80_busdelay >> 8);
Pico.t.z80_busdelay &= 0xff;
} }
else else
{ {
if ((PicoIn.opt & POPT_EN_Z80) && !Pico.m.z80_reset) { if ((PicoIn.opt & POPT_EN_Z80) && !Pico.m.z80_reset) {
// Z80 grants bus 2 cycles after the next M cycle, even within an insn
// simulate this by accumulating the last insn overhang in busdelay
unsigned granted = z80_cycles_from_68k() + 6;
pprof_start(m68k); pprof_start(m68k);
PicoSyncZ80(SekCyclesDone()); PicoSyncZ80(SekCyclesDone());
Pico.t.z80_busdelay += (Pico.t.z80c_cnt - granted) << 8;
Pico.t.z80c_cnt = granted;
pprof_end_sub(m68k); pprof_end_sub(m68k);
} }
} }
@ -553,7 +559,7 @@ void NOINLINE ctl_write_z80reset(u32 d)
} }
else else
{ {
Pico.t.z80c_cnt = z80_cycles_from_68k() + 1; Pico.t.z80c_cnt = z80_cycles_from_68k() + 2;
z80_reset(); z80_reset();
} }
Pico.m.z80_reset = d; Pico.m.z80_reset = d;
@ -675,7 +681,8 @@ static void PicoWrite16_sram(u32 a, u32 d)
static u32 PicoRead8_z80(u32 a) static u32 PicoRead8_z80(u32 a)
{ {
u32 d = 0xff; u32 d = 0xff;
if ((Pico.m.z80Run | Pico.m.z80_reset) && !(PicoIn.quirks & PQUIRK_NO_Z80_BUS_LOCK)) { if ((Pico.m.z80Run | Pico.m.z80_reset | (z80_cycles_from_68k() < Pico.t.z80c_cnt)) &&
!(PicoIn.quirks & PQUIRK_NO_Z80_BUS_LOCK)) {
elprintf(EL_ANOMALY, "68k z80 read with no bus! [%06x] @ %06x", a, SekPc); elprintf(EL_ANOMALY, "68k z80 read with no bus! [%06x] @ %06x", a, SekPc);
// open bus. Pulled down if MegaCD2 is attached. // open bus. Pulled down if MegaCD2 is attached.
return (PicoIn.AHW & PAHW_MCD ? 0 : d); return (PicoIn.AHW & PAHW_MCD ? 0 : d);
@ -1356,8 +1363,9 @@ static void access_68k_bus(int delay) // bus delay as Q8
// 68k bus access delay for z80. The fractional part needs to be accumulated // 68k bus access delay for z80. The fractional part needs to be accumulated
// until an additional cycle is full. That is then added to the integer part. // until an additional cycle is full. That is then added to the integer part.
Pico.t.z80_busdelay = (delay&0xff) + (Pico.t.z80_busdelay&0xff); // accumulate Pico.t.z80_busdelay += (delay&0xff); // accumulate
z80_subCLeft((delay>>8) + (Pico.t.z80_busdelay>>8)); z80_subCLeft((delay>>8) + (Pico.t.z80_busdelay>>8));
Pico.t.z80_busdelay &= 0xff; // leftover cycle fraction
// don't use SekCyclesBurn() here since the Z80 doesn't run in cycle lock to // don't use SekCyclesBurn() here since the Z80 doesn't run in cycle lock to
// the 68K. Count the stolen cycles to be accounted later in the 68k CPU runs // the 68K. Count the stolen cycles to be accounted later in the 68k CPU runs
Pico.t.z80_buscycles += 8; Pico.t.z80_buscycles += 8;

2
pico/pico_cmn.c
View file

@ -80,7 +80,7 @@ static __inline void SekAimM68k(int cyc, int mult)
static __inline void SekRunM68k(int cyc) static __inline void SekRunM68k(int cyc)
{ {
// TODO 0x100 would by 2 cycles/128, moreover far too sensitive // TODO 0x100 would be 2 cycles/128, moreover far too sensitive
SekAimM68k(cyc, 0x10c); // OutRunners, testpico, VDPFIFOTesting SekAimM68k(cyc, 0x10c); // OutRunners, testpico, VDPFIFOTesting
SekSyncM68k(0); SekSyncM68k(0);
} }