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[Core/CD] improved accuracy of CDC transfer to Main-CPU & Sub-CPU (verified on real hardware, cf. Krikzz's mcd-verificator)

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ekeeke 2023-11-26 16:27:15 +01:00
parent fcb6620202
commit 52b4f78b82
5 changed files with 100 additions and 48 deletions
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1
HISTORY.txt
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@ -24,6 +24,7 @@ Genesis Plus GX 1.7.5 (xx/xx/xxxx) (Eke-Eke)
* improved Timer interrupt timings and CDD interrupt accuracy (fixes audio stutters during Popful Mail FMV)
* improved CDC emulation (fixes random freezes during Jeopardy & ESPN Sunday Night NFL intro)
* improved accuracy of Main-CPU & Sub-CPU access to CDC registers (verified on real hardware, cf. Krikzz's mcd-verificator)
* improved accuracy of CDC transfer to Main-CPU & Sub-CPU (verified on real hardware, cf. Krikzz's mcd-verificator)
* improved emulation of mirrored memory areas
* improved savestate format
* improved Sub-CPU synchronization with Main-CPU (fixes "Soul Star")

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87
core/cd_hw/cdc.c
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@ -433,7 +433,7 @@ void cdc_reg_w(unsigned char data)
/* set !DTBSY and !DTEN */
cdc.ifstat &= ~(BIT_DTBSY | BIT_DTEN);
/* clear EDT & DSR bits (SCD register $04) */
/* clear EDT & DSR bits (gate-array register $04) */
scd.regs[0x04>>1].byte.h &= 0x07;
/* setup data transfer destination */
@ -442,8 +442,52 @@ void cdc_reg_w(unsigned char data)
case 2: /* MAIN-CPU host read */
case 3: /* SUB-CPU host read */
{
/* set DSR bit (SCD register $04) */
/* read 16-bit word from CDC RAM buffer (big-endian format) into gate-array register $08 */
/* Note: on real-hardware, 16-bit word is not immediately available, cf. https://github.com/MiSTer-devel/MegaCD_MiSTer/blob/master/docs/mcd%20logs/dma_sub_read.jpg for transfer timings */
scd.regs[0x08>>1].w = READ_WORD(cdc.ram, cdc.dac.w & 0x3ffe);
#ifdef LOG_CDC
error("CDC host read 0x%04x -> 0x%04x (dbc=0x%x) (%X)\n", cdc.dac.w, scd.regs[0x08>>1].w, cdc.dbc.w, s68k.pc);
#endif
/* set DSR bit (gate-array register $04) */
scd.regs[0x04>>1].byte.h |= 0x40;
/* increment data address counter */
cdc.dac.w += 2;
/* decrement data byte counter */
cdc.dbc.w -= 2;
/* end of transfer ? */
if ((int16)cdc.dbc.w < 0)
{
/* reset data byte counter (DBCH bits 4-7 should also be set to 1) */
cdc.dbc.w = 0xffff;
/* clear !DTEN and !DTBSY */
cdc.ifstat |= (BIT_DTBSY | BIT_DTEN);
/* pending Data Transfer End interrupt */
cdc.ifstat &= ~BIT_DTEI;
/* Data Transfer End interrupt enabled ? */
if (cdc.ifctrl & BIT_DTEIEN)
{
/* pending level 5 interrupt */
scd.pending |= (1 << 5);
/* level 5 interrupt enabled ? */
if (scd.regs[0x32>>1].byte.l & 0x20)
{
/* update IRQ level */
s68k_update_irq((scd.pending & scd.regs[0x32>>1].byte.l) >> 1);
}
}
/* set EDT bit (gate-array register $04) */
scd.regs[0x04>>1].byte.h |= 0x80;
}
break;
}
@ -727,14 +771,25 @@ unsigned char cdc_reg_r(void)
unsigned short cdc_host_r(void)
{
/* check if data is available */
/* read CDC buffered data (gate-array register $08) */
uint16 data = scd.regs[0x08>>1].w;
/* check if host data transfer is enabled */
if (scd.regs[0x04>>1].byte.h & 0x40)
{
/* read 16-bit word from CDC RAM buffer (big-endian format) */
uint16 data = READ_WORD(cdc.ram, cdc.dac.w & 0x3ffe);
/* check if EDT bit (gate-array register $04) is set (host data transfer is finished) */
if (scd.regs[0x04>>1].byte.h & 0x80)
{
/* clear DSR bit (gate-array register $04) */
scd.regs[0x04>>1].byte.h &= ~0x40;
}
else
{
/* read next 16-bit word from CDC RAM buffer (big-endian format) into gate-array register $08 */
/* Note: on real-hardware, 16-bit word is not immediately available, cf. https://github.com/MiSTer-devel/MegaCD_MiSTer/blob/master/docs/mcd%20logs/dma_sub_read.jpg for transfer timings */
scd.regs[0x08>>1].w = READ_WORD(cdc.ram, cdc.dac.w & 0x3ffe);
#ifdef LOG_CDC
error("CDC host read 0x%04x -> 0x%04x (dbc=0x%x) (%X)\n", cdc.dac.w, data, cdc.dbc.w, s68k.pc);
error("CDC host read 0x%04x -> 0x%04x (dbc=0x%x) (%X)\n", cdc.dac.w, scd.regs[0x08>>1].w, cdc.dbc.w, s68k.pc);
#endif
/* increment data address counter */
@ -744,10 +799,10 @@ unsigned short cdc_host_r(void)
cdc.dbc.w -= 2;
/* end of transfer ? */
if ((int16)cdc.dbc.w <= 0)
if ((int16)cdc.dbc.w < 0)
{
/* reset data byte counter (DBCH bits 4-7 should be set to 1) */
cdc.dbc.w = 0xf000;
/* reset data byte counter (DBCH bits 4-7 should also be set to 1) */
cdc.dbc.w = 0xffff;
/* clear !DTEN and !DTBSY */
cdc.ifstat |= (BIT_DTBSY | BIT_DTEN);
@ -769,15 +824,11 @@ unsigned short cdc_host_r(void)
}
}
/* clear DSR bit & set EDT bit (SCD register $04) */
scd.regs[0x04>>1].byte.h = (scd.regs[0x04>>1].byte.h & 0x07) | 0x80;
/* set EDT bit (gate-array register $04) */
scd.regs[0x04>>1].byte.h |= 0x80;
}
}
}
return data;
}
#ifdef LOG_CDC
error("error reading CDC host (data transfer disabled)\n");
#endif
return 0xffff;
}