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[Core/CPU] fixed Z80 registers initial state, added proper initialization when using PBC (verified on real hardware by Charles McDonald)

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This commit is contained in:
EkeEke 2013-02-02 02:33:14 +01:00
parent a3519baa93
commit 7579d92c25
3 changed files with 29 additions and 20 deletions
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27
source/genesis.c
View File

@ -327,8 +327,33 @@ void gen_reset(int hard_reset)
/* reset Z80 */
z80_reset();
}
/* some Z80 registers need to be initialized on Power ON */
if (hard_reset)
{
/* Power Base Converter specific */
if (system_hw == SYSTEM_PBC)
{
/* startup code logic (verified on real hardware): */
/* 21 01 E1 : LD HL, $E101
25 -- -- : DEC H
F9 -- -- : LD SP,HL
C7 -- -- : RST $00
01 01 -- : LD BC, $xx01
*/
Z80.hl.w.l = 0xE001;
Z80.sp.w.l = 0xDFFF;
Z80.r = 4;
}
/* Master System specific (when BIOS is disabled) */
else if ((system_hw & SYSTEM_SMS) && (!(config.bios & 1) || !(system_bios & SYSTEM_SMS)))
{
/* usually done by BIOS & required by some SMS games that don't initialize SP */
Z80.sp.w.l = 0xDFFF;
}
}
}
/*-----------------------------------------------------------------------*/
/* OS ROM / TMSS register control functions (Genesis mode) */

21
source/z80/z80.c
View File

@ -31,6 +31,7 @@
* This Z80 emulator assumes a ZiLOG NMOS model.
*
* Additional changes [Eke-Eke]:
* - Removed z80_burn function (unused)
* - Discarded multi-chip support (unused)
* - Fixed cycle counting for FD and DD prefixed instructions
* - Fixed behavior of chained FD and DD prefixes (R register should be only incremented by one
@ -3358,11 +3359,9 @@ void z80_init(const void *config, int (*irqcallback)(int))
Z80.daisy = config;
Z80.irq_callback = irqcallback;
/* Reset registers to their initial values (NB: should be random on real hardware) */
AF = BC = DE = HL = 0;
/* Clear registers values (NB: should be random on real hardware ?) */
AF = BC = DE = HL = SP = IX = IY =0;
F = ZF; /* Zero flag is set */
IX = IY = 0xffff; /* IX and IY are FFFF after a reset! (from MAME) */
SP = 0xdfff; /* required by some SMS games that don't initialize SP */
/* setup cycle tables */
cc[Z80_TABLE_op] = cc_op;
@ -3411,20 +3410,6 @@ void z80_run(unsigned int cycles)
}
}
/****************************************************************************
* Burn 'cycles' T-states. Adjust R register for the lost time
****************************************************************************/
void z80_burn(unsigned int cycles)
{
if( cycles > 0 )
{
/* NOP takes 4 cycles per instruction */
int n = (cycles + 3) / 4;
R += n;
Z80.cycles += 4 * n * 15;
}
}
/****************************************************************************
* Get all registers in given buffer
****************************************************************************/

1
source/z80/z80.h
View File

@ -62,7 +62,6 @@ extern unsigned char (*z80_readport)(unsigned int port);
extern void z80_init(const void *config, int (*irqcallback)(int));
extern void z80_reset (void);
extern void z80_run(unsigned int cycles);
extern void z80_burn(unsigned int cycles);
extern void z80_get_context (void *dst);
extern void z80_set_context (void *src);
extern void z80_set_irq_line(unsigned int state);