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[Core/CD] fixed byte access to word-only registers (verified on real hardware, cf. Krikzz's mcd-verificator)

This commit is contained in:
ekeeke 2024-02-22 14:14:27 +01:00
parent f09c97336e
commit 49a289df89
5 changed files with 19 additions and 5 deletions
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1
HISTORY.txt
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@ -53,6 +53,7 @@ Genesis Plus GX 1.7.5 (xx/xx/xxxx) (Eke-Eke)
* fixed BOOT ROM level 4 interrupt vector upper word value (verified on real hardware, cf. Krikzz's mcd-verificator)
* fixed access to "write-only" communication flags (verified on real hardware by Notaz)
* fixed access to Sub-CPU "read-only" communication registers (fixes Round 5 Boss freeze in Streets of Rage / Sega Classics Arcade Collection)
* fixed byte access to word-only registers (verified on real hardware, cf. Krikzz's mcd-verificator)
* fixed byte access to memory mode, timer and font color registers at even address (verified on real hardware, cf. Krikzz's mcd-verificator)
* fixed byte access to font data registers
* fixed memory mode register bits masking when read from MAIN-CPU and SUB-CPU (verified on real hardware, cf. Krikzz's mcd-verificator)

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builds/genesis_plus_gx_libretro.dll
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23
core/cd_hw/scd.c
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@ -802,6 +802,8 @@ INLINE void word_ram_switch(uint8 mode)
}
}
static void scd_write_word(unsigned int address, unsigned int data);
static void scd_write_byte(unsigned int address, unsigned int data)
{
/* PCM area (8K) mirrored into $xF0000-$xF7FFF */
@ -1123,29 +1125,40 @@ static void scd_write_byte(unsigned int address, unsigned int data)
default:
{
uint16 reg_16 = address & 0x1fe;
/* SUB-CPU communication words */
if ((address & 0x1f0) == 0x20)
if ((reg_16 >= 0x20) && (reg_16 <= 0x2f))
{
s68k_poll_sync(1 << ((address - 0x10) & 0x1f));
}
/* MAIN-CPU communication words */
else if ((address & 0x1f0) == 0x10)
else if ((reg_16 >= 0x10) && (reg_16 <= 0x1f))
{
/* read-only (Sega Classic Arcade Collection) */
return;
}
/* word-only registers */
else if (((reg_16 >= 0x08) && (reg_16 <= 0x0d)) ||
((reg_16 >= 0x34) && (reg_16 <= 0x35)) ||
((reg_16 >= 0x5a) && (reg_16 <= 0x67)))
{
scd_write_word(address, (data << 8) | (data & 0xff));
return;
}
/* default registers */
if (address & 1)
{
/* register LSB */
scd.regs[(address >> 1) & 0xff].byte.l = data;
scd.regs[reg_16 >> 1].byte.l = data;
return;
}
/* register MSB */
scd.regs[(address >> 1) & 0xff].byte.h = data;
scd.regs[reg_16 >> 1].byte.h = data;
return;
}
}
@ -1412,7 +1425,7 @@ static void scd_write_word(unsigned int address, unsigned int data)
return;
}
case 0x0c: /* Stopwatch (word access only) */
case 0x0c: /* Stopwatch */
{
/* synchronize the counter with SUB-CPU */
int ticks = (s68k.cycles - scd.stopwatch) / TIMERS_SCYCLES_RATIO;