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6502.c
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/*
** Oricutron
** Copyright (C) 2009-2014 Peter Gordon
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the GNU General Public License
** as published by the Free Software Foundation, version 2
** of the License.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
**
** 6502 emulation
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "system.h"
#include "6502.h"
#define ILLEGALS
void dbg_printf( char *fmt, ... );
#if defined(DEBUG_CPU_TRACE) && DEBUG_CPU_TRACE > 0
void mon_traceinst(struct m6502 *cpu);
#endif
// These are the default read/write routines.
// You need to overwrite these with your own ones if you want
// the CPU to do anything other than constantly execute brk
// instructions :-)
static void nullwrite( struct m6502 *cpu, unsigned short addr, unsigned char data )
{
}
static unsigned char nullread( struct m6502 *cpu, unsigned short addr )
{
return 0;
}
/*
** Initialise an already allocated 6502 instance.
** The userdata param is just used to fill in the
** cpu->userdata field.
*/
void m6502_init( struct m6502 *cpu, void *userdata, SDL_bool nukebreakpoints )
{
int i;
cpu->rastercycles = 0;
cpu->icycles = 0;
cpu->cycles = 0;
cpu->write = nullwrite;
cpu->read = nullread;
if( nukebreakpoints )
{
for( i=0; i<16; i++ )
{
cpu->breakpoints[i] = -1;
cpu->membreakpoints[i].flags = 0;
}
cpu->anybp = SDL_FALSE;
cpu->anymbp = SDL_FALSE;
}
cpu->userdata = userdata;
}
/*
** Resets the 6502 cpu to powerup state */
void m6502_reset( struct m6502 *cpu )
{
cpu->a = cpu->x = cpu->y = 0;
cpu->sp = 0xff;
cpu->f_c = 0;
cpu->f_z = 1;
cpu->f_i = 0;
cpu->f_d = 0;
cpu->f_b = 0;
cpu->f_v = 0;
cpu->f_n = 0;
cpu->pc = (cpu->read( cpu, 0xfffd )<<8) | cpu->read( cpu, 0xfffc );
cpu->lastpc = 0;
cpu->nmi = SDL_FALSE;
cpu->irq = 0;
cpu->nmicount = 0;
}
// Macros to set flags for various instructions
#define FLAG_ZCN(n) cpu->f_z = ((n)&0xff) == 0;\
cpu->f_c = ((n)&0xff00) != 0;\
cpu->f_n = ((n)&0x80) != 0
#define FLAG_SZCN(n) cpu->f_z = ((n)&0xff) == 0;\
cpu->f_c = ((n)&0xff00) == 0;\
cpu->f_n = ((n)&0x80) != 0
#define FLAG_ZN(n) cpu->f_z = (n) == 0;\
cpu->f_n = ((n)&0x80) != 0
// Macro to perform ADC logic
#define DO_ADC if( cpu->f_d )\
{\
r = (cpu->a&0xf)+(v&0xf)+cpu->f_c;\
if( r > 9 ) r += 6;\
t = (cpu->a>>4)+(v>>4)+(r>15?1:0);\
if( t > 9 ) t += 6;\
cpu->a = (r&0xf)|(t<<4);\
cpu->f_c = t>15 ? 1 : 0;\
cpu->f_z = cpu->a!=0;\
cpu->f_n = cpu->a&0x80;\
} else {\
r = cpu->a + v + cpu->f_c;\
cpu->f_v = (~(cpu->a^v)&(cpu->a^r)) & FF_N ? 1 : 0;\
FLAG_ZCN(r);\
cpu->a = r;\
}
// Macro to perform AND logic
#define DO_AND cpu->a &= v;\
FLAG_ZN(cpu->a)
// Macro to perform ASL logic
#define DO_ASL(s) cpu->f_c = ((s)&0x80) != 0;\
s <<= 1;\
FLAG_ZN(s);
// Macro to perform ORA logic
#define DO_ORA cpu->a |= v;\
FLAG_ZN(cpu->a)
// Macro to perform ROL logic
#define DO_ROL(s) r = (s<<1)|cpu->f_c;\
cpu->f_c = r&0x100 ? 1 : 0;\
s = r;\
FLAG_ZN(s)
// Macro to perform ROR logic
#define DO_ROR(s) r = (s)&1;\
s = (s>>1)|(cpu->f_c<<7);\
cpu->f_c = r;\
FLAG_ZN(s)
// Macro to perform EOR logic
#define DO_EOR cpu->a ^= v;\
FLAG_ZN(cpu->a)
// Macro to perform LSR logic
#define DO_LSR(s) cpu->f_c = (s)&0x01;\
s >>= 1;\
FLAG_ZN(s)
// Macro to perform SBC logic
#define DO_SBC if( cpu->f_d )\
{\
r = (cpu->a&0xf) - (v&0xf) - (cpu->f_c^1);\
if( r&0x10 ) r -= 6;\
t = (cpu->a>>4) - (v>>4) - ((r&0x10)>>4);\
if( t&0x10 ) t -= 6;\
cpu->a = (r&0xf)|(t<<4);\
cpu->f_c = (t>15) ? 0 : 1;\
cpu->f_z = cpu->a!=0;\
cpu->f_n = cpu->a&0x80;\
} else {\
r = (cpu->a - v) - (cpu->f_c^1);\
cpu->f_v = ((cpu->a^v)&(cpu->a^r)) & FF_N ? 1 : 0;\
FLAG_SZCN(r);\
cpu->a = r;\
}
#define BADDR_ZP baddr = cpu->read( cpu, cpu->pc )
#define BADDR_ZPX baddr = (cpu->read( cpu, cpu->pc ) + cpu->x)&0xff
#define BADDR_ZPY baddr = (cpu->read( cpu, cpu->pc ) + cpu->y)&0xff
#define BADDR_ABS baddr = (cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc )
#define BADDR_ABX baddr = ((cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc ))+cpu->x
#define BADDR_ABY baddr = ((cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc ))+cpu->y
#define BADDR_ZIX baddr = (unsigned char)(cpu->read( cpu, cpu->pc )+cpu->x); baddr = (cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr )
#define BADDR_ZIY baddr = cpu->read( cpu, cpu->pc ); baddr = ((cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ))+cpu->y
#define NBADDR_ZP baddr = cpu->read( cpu, cpu->calcpc+1 )
#define NBADDR_ZPX baddr = (cpu->read( cpu, cpu->calcpc+1 ) + cpu->x)&0xff
#define NBADDR_ZPY baddr = (cpu->read( cpu, cpu->calcpc+1 ) + cpu->y)&0xff
#define NBADDR_ABS baddr = (cpu->read( cpu, cpu->calcpc+2 )<<8) | cpu->read( cpu, cpu->calcpc+1 )
#define NBADDR_ABX baddr = ((cpu->read( cpu, cpu->calcpc+2 )<<8) | cpu->read( cpu, cpu->calcpc+1 ))+cpu->x
#define NBADDR_ABY baddr = ((cpu->read( cpu, cpu->calcpc+2 )<<8) | cpu->read( cpu, cpu->calcpc+1 ))+cpu->y
#define NBADDR_ZIX baddr = (unsigned char)(cpu->read( cpu, cpu->calcpc+1 )+cpu->x); baddr = (cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr )
#define NBADDR_ZIY baddr = cpu->read( cpu, cpu->calcpc+1 ); baddr = ((cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ))+cpu->y
#define R_BADDR_ZP NBADDR_ZP; raddr = baddr; rlen = 1
#define W_BADDR_ZP NBADDR_ZP; waddr = baddr; wlen = 1
#define RW_BADDR_ZP NBADDR_ZP; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ZPX NBADDR_ZPX; raddr = baddr; rlen = 1
#define W_BADDR_ZPX NBADDR_ZPX; waddr = baddr; wlen = 1
#define RW_BADDR_ZPX NBADDR_ZPX; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ZPY NBADDR_ZPY; raddr = baddr; rlen = 1
#define W_BADDR_ZPY NBADDR_ZPY; waddr = baddr; wlen = 1
#define RW_BADDR_ZPY NBADDR_ZPY; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ABS NBADDR_ABS; raddr = baddr; rlen = 1
#define W_BADDR_ABS NBADDR_ABS; waddr = baddr; wlen = 1
#define RW_BADDR_ABS NBADDR_ABS; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ABX NBADDR_ABX; raddr = baddr; rlen = 1
#define W_BADDR_ABX NBADDR_ABX; waddr = baddr; wlen = 1
#define RW_BADDR_ABX NBADDR_ABX; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ABY NBADDR_ABY; raddr = baddr; rlen = 1
#define W_BADDR_ABY NBADDR_ABY; waddr = baddr; wlen = 1
#define RW_BADDR_ABY NBADDR_ABY; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ZIX NBADDR_ZIX; raddr = baddr; rlen = 1
#define W_BADDR_ZIX NBADDR_ZIX; waddr = baddr; wlen = 1
#define RW_BADDR_ZIX NBADDR_ZIX; waddr = raddr = baddr; wlen = rlen = 1
#define R_BADDR_ZIY NBADDR_ZIY; raddr = baddr; rlen = 1
#define W_BADDR_ZIY NBADDR_ZIY; waddr = baddr; wlen = 1
#define RW_BADDR_ZIY NBADDR_ZIY; waddr = raddr = baddr; wlen = rlen = 1
// Macros for each addressing mode of the 6502
#define READ_IMM v=cpu->read( cpu, cpu->pc++ )
#define READ_ZP v=cpu->read( cpu, cpu->read( cpu, cpu->pc++ ) )
#define READ_ZPX v=cpu->read( cpu, (cpu->read( cpu, cpu->pc++ ) + cpu->x)&0xff )
#define READ_ZPY v=cpu->read( cpu, (cpu->read( cpu, cpu->pc++ ) + cpu->y)&0xff )
#define READ_ABS v=cpu->read( cpu, (cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc ) ); cpu->pc+=2
#define READ_ABX BADDR_ABX; v = cpu->read( cpu, baddr ); cpu->pc+=2
#define READ_ABY BADDR_ABY; v = cpu->read( cpu, baddr ); cpu->pc+=2
#define READ_ZIX BADDR_ZIX; v = cpu->read( cpu, baddr ); cpu->pc++
#define READ_ZIY BADDR_ZIY; v = cpu->read( cpu, baddr ); cpu->pc++
#define KREAD_ZP baddr = cpu->read( cpu, cpu->pc++ ); v = cpu->read( cpu, baddr )
#define KREAD_ZPX baddr = (unsigned char)(cpu->read( cpu, cpu->pc++ )+cpu->x); v = cpu->read( cpu, baddr )
#define KREAD_ABS baddr = (cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc ); v=cpu->read( cpu, baddr ); cpu->pc+=2
// .. and for writing
#define WRITE_ZP(n) cpu->write( cpu, cpu->read( cpu, cpu->pc++ ), n )
#define WRITE_ZPX(n) cpu->write( cpu, (cpu->read( cpu, cpu->pc++ ) + cpu->x)&0xff, n )
#define WRITE_ZPY(n) cpu->write( cpu, (cpu->read( cpu, cpu->pc++ ) + cpu->y)&0xff, n )
#define WRITE_ABS(n) cpu->write( cpu, (cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc ), n ); cpu->pc+=2
#define WRITE_ABX(n) baddr = ((cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc )); cpu->write( cpu, baddr + cpu->x, n ); cpu->pc+=2
#define WRITE_ABY(n) baddr = ((cpu->read( cpu, cpu->pc+1 )<<8) | cpu->read( cpu, cpu->pc )); cpu->write( cpu, baddr + cpu->y, n ); cpu->pc+=2
#define WRITE_ZIX(n) baddr = (unsigned char)(cpu->read( cpu, cpu->pc++ )+cpu->x); cpu->write( cpu, (cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ), n )
#define WRITE_ZIY(n) baddr = cpu->read( cpu, cpu->pc++ ); baddr = (cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ); cpu->write( cpu, baddr + cpu->y, n )
// Page check to see if an offset takes you out of the base page (baddr)
#define PAGECHECK(n) ( ((baddr+n)&0xff00) != (baddr&0xff00) )
// Same as above, but when (baddr+n) is already calculated (in cpu->baddr)
#define CPAGECHECK ((cpu->baddr&0xff00) != (baddr&0xff00))
// Page check to see if a branch takes you out of the current page
#define BPAGECHECK ( (cpu->baddr&0xff00) != (cpu->calcpc&0xff00) )
// Macro to perform branch logic
#define BRANCH(condition) if( condition ) cpu->pc = cpu->baddr; else cpu->pc++;
// Macro to calculate cycles of a branch instruction
#define IBRANCH(condition) cpu->icycles = 2;\
if( condition )\
{\
cpu->baddr = cpu->calcpc+2+((signed char)cpu->read( cpu, cpu->calcpc+1 ));\
cpu->icycles++;\
if( BPAGECHECK ) cpu->icycles++;\
}\
// Macros to simplify pushing and popping
#define PUSHB(n) cpu->write( cpu, (cpu->sp--)+0x100, n )
#define POPB cpu->read( cpu, (++cpu->sp)+0x100 )
#define PUSHW(n) PUSHB( n>>8 ); PUSHB( n )
#define POPW(n) n = (cpu->read(cpu,((cpu->sp+2)&0xff)+0x100)<<8)|cpu->read(cpu,((cpu->sp+1)&0xff)+0x100); cpu->sp+=2
// Get the number of cycles the NEXT cpu instruction will take
// Returns TRUE if we've hit some kind of breakpoint
SDL_bool m6502_set_icycles( struct m6502 *cpu, SDL_bool dobp, char *bpmsg )
{
unsigned short baddr;
unsigned int extra = 0;
int i;
if( cpu->nmicount > 0 )
{
cpu->nmicount--;
if( !cpu->nmicount )
cpu->nmi = SDL_FALSE;
}
if( cpu->nmi )
{
extra = 7;
cpu->calcpc = (cpu->read( cpu, 0xfffb )<<8)|cpu->read( cpu, 0xfffa );
cpu->calcint = 2;
} else if( ( cpu->irq ) && ( cpu->f_i == 0 ) ) {
extra = 7;
cpu->calcpc = (cpu->read( cpu, 0xffff )<<8)|cpu->read( cpu, 0xfffe );
cpu->calcint = 1;
}
else
{
cpu->calcpc = cpu->pc;
cpu->calcint = 0;
}
cpu->calcop = cpu->read( cpu, cpu->calcpc );
if( dobp )
{
if( cpu->anybp )
{
for( i=0; i<16; i++ )
{
if( ( cpu->breakpoints[i] != -1 ) && ( cpu->calcpc == cpu->breakpoints[i] ) )
{
if( (cpu->breakpoint_flags[i] & MBPF_RESETCYCLES) == MBPF_RESETCYCLES ) cpu->cycles = 0;
if( (cpu->breakpoint_flags[i] & MBPF_RESETCYCLESCONTINUE) != MBPF_RESETCYCLESCONTINUE ) return SDL_TRUE;
}
}
}
if( cpu->anymbp )
{
unsigned short waddr, raddr, wlen, rlen;
waddr = raddr = 0;
wlen = rlen = 0;
// Going to read or write?
switch( cpu->calcop )
{
case 0x00: // { "BRK", AM_IMP }, // 00
waddr = (cpu->sp+0x100)-3;
wlen = 3;
break;
case 0x40: // { "RTI", AM_IMP }, // 40
waddr = (cpu->sp+0x100);
wlen = 3;
break;
case 0x08: // { "PHP", AM_IMP }, // 08
case 0x48: // { "PHA", AM_IMP }, // 48
waddr = (cpu->sp+0x100)-1;
wlen = 1;
break;
case 0x28: // { "PLP", AM_IMP }, // 28
case 0x68: // { "PLA", AM_IMP }, // 68
raddr = cpu->sp+0x100;
rlen = 1;
break;
case 0x60: // { "RTS", AM_IMP }, // 60
raddr = cpu->sp+0x100;
rlen = 2;
break;
case 0x20: // { "JSR", AM_ABS }, // 20
waddr = (cpu->sp+0x100)-2;
wlen = 2;
break;
case 0x06: // { "ASL", AM_ZP }, // 06
case 0x26: // { "ROL", AM_ZP }, // 26
case 0x46: // { "LSR", AM_ZP }, // 46
case 0x66: // { "ROR", AM_ZP }, // 66
case 0xC6: // { "DEC", AM_ZP }, // C6
case 0xE6: // { "INC", AM_ZP }, // E6
#ifdef ILLEGALS
case 0xC7: // { "DCP", AM_ZP }, // C7 (illegal)
case 0xE7: // { "ISC", AM_ZP }, // E7 (illegal)
case 0x27: // { "RLA", AM_ZP }, // 27 (illegal)
case 0x67: // { "RRA", AM_ZP }, // 67 (illegal)
case 0x07: // { "SLO", AM_ZP }, // 07 (illegal)
case 0x47: // { "SRE", AM_ZP }, // 47 (illegal)
#endif
RW_BADDR_ZP;
break;
case 0x0E: // { "ASL", AM_ABS }, // 0E
case 0x2E: // { "ROL", AM_ABS }, // 2E
case 0x4E: // { "LSR", AM_ABS }, // 4E
case 0x6E: // { "ROR", AM_ABS }, // 6E
case 0xCE: // { "DEC", AM_ABS }, // CE
case 0xEE: // { "INC", AM_ABS }, // EE
#ifdef ILLEGALS
case 0xCF: // { "DCP", AM_ABS }, // CF (illegal)
case 0xEF: // { "ISC", AM_ABS }, // EF (illegal)
case 0x2F: // { "RLA", AM_ABS }, // 2F (illegal)
case 0x6F: // { "RRA", AM_ABS }, // 6F (illegal)
case 0x0F: // { "SLO", AM_ABS }, // 0F (illegal)
case 0x4F: // { "SRE", AM_ABS }, // 4F (illegal)
#endif
RW_BADDR_ABS;
break;
case 0x1E: // { "ASL", AM_ABX }, // 1E
case 0x3E: // { "ROL", AM_ABX }, // 3E
case 0x5E: // { "LSR", AM_ABX }, // 5E
case 0x7E: // { "ROR", AM_ABX }, // 7E
case 0xDE: // { "DEC", AM_ABX }, // DE
case 0xFE: // { "INC", AM_ABX }, // FE
#ifdef ILLEGALS
case 0xDF: // { "DCP", AM_ABX }, // DF (illegal)
case 0xFF: // { "ISC", AM_ABX }, // FF (illegal)
case 0x3F: // { "RLA", AM_ABX }, // 3F (illegal)
case 0x7F: // { "RRA", AM_ABX }, // 7F (illegal)
case 0x1F: // { "SLO", AM_ABX }, // 1F (illegal)
case 0x5F: // { "SRE", AM_ABX }, // 5F (illegal)
#endif
RW_BADDR_ABX;
break;
case 0x16: // { "ASL", AM_ZPX }, // 16
case 0x36: // { "ROL", AM_ZPX }, // 36
case 0x56: // { "LSR", AM_ZPX }, // 56
case 0x76: // { "ROR", AM_ZPX }, // 76
case 0xD6: // { "DEC", AM_ZPX }, // D6
case 0xF6: // { "INC", AM_ZPX }, // F6
#ifdef ILLEGALS
case 0xD7: // { "DCP", AM_ZPX }, // D7 (illegal)
case 0xF7: // { "ISC", AM_ZPX }, // F7 (illegal)
case 0x37: // { "RLA", AM_ZPX }, // 37 (illegal)
case 0x77: // { "RRA", AM_ZPX }, // 77 (illegal)
case 0x17: // { "SLO", AM_ZPX }, // 17 (illegal)
case 0x57: // { "SRE", AM_ZPX }, // 57 (illegal)
#endif
RW_BADDR_ZPX;
break;
#ifdef ILLEGALS
case 0xDB: // { "DCP", AM_ABY }, // DB (illegal)
case 0xFB: // { "ISC", AM_ABY }, // FB (illegal)
case 0x3B: // { "RLA", AM_ABY }, // 3B (illegal)
case 0x7B: // { "RRA", AM_ABY }, // 7B (illegal)
case 0x1B: // { "SLO", AM_ABY }, // 1B (illegal)
case 0x5B: // { "SRE", AM_ABY }, // 5B (illegal)
RW_BADDR_ABY;
break;
case 0xC3: // { "DCP", AM_ZIX }, // C3 (illegal)
case 0xE3: // { "ISC", AM_ZIX }, // E3 (illegal)
case 0x23: // { "RLA", AM_ZIX }, // 23 (illegal)
case 0x63: // { "RRA", AM_ZIX }, // 63 (illegal)
case 0x03: // { "SLO", AM_ZIX }, // 03 (illegal)
case 0x43: // { "SRE", AM_ZIX }, // 43 (illegal)
RW_BADDR_ZIX;
break;
case 0xD3: // { "DCP", AM_ZIY }, // D3 (illegal)
case 0xF3: // { "ISC", AM_ZIY }, // F3 (illegal)
case 0x33: // { "RLA", AM_ZIY }, // 33 (illegal)
case 0x73: // { "RRA", AM_ZIY }, // 73 (illegal)
case 0x13: // { "SLO", AM_ZIY }, // 13 (illegal)
case 0x53: // { "SRE", AM_ZIY }, // 53 (illegal)
RW_BADDR_ZIY;
break;
#endif
case 0x01: // { "ORA", AM_ZIX }, // 01
case 0x21: // { "AND", AM_ZIX }, // 21
case 0x41: // { "EOR", AM_ZIX }, // 41
case 0x61: // { "ADC", AM_ZIX }, // 61
case 0xA1: // { "LDA", AM_ZIX }, // A1
case 0xC1: // { "CMP", AM_ZIX }, // C1
case 0xE1: // { "SBC", AM_ZIX }, // E1
#ifdef ILLEGALS
case 0xA3: // { "LAX", AM_ZIX }, // A3 (illegal)
#endif
R_BADDR_ZIX;
break;
case 0x11: // { "ORA", AM_ZIY }, // 11
case 0x31: // { "AND", AM_ZIY }, // 31
case 0x51: // { "EOR", AM_ZIY }, // 51
case 0x71: // { "ADC", AM_ZIY }, // 71
case 0xB1: // { "LDA", AM_ZIY }, // B1
case 0xD1: // { "CMP", AM_ZIY }, // D1
case 0xF1: // { "SBC", AM_ZIY }, // F1
case 0xBB: // { "LAS", AM_ZIY }, // BB
#ifdef ILLEGALS
case 0xB3: // { "LAX", AM_ZIY }, // B3 (illegal)
#endif
R_BADDR_ZIY;
break;
case 0x05: // { "ORA", AM_ZP }, // 05
case 0x24: // { "BIT", AM_ZP }, // 24
case 0x25: // { "AND", AM_ZP }, // 25
case 0x45: // { "EOR", AM_ZP }, // 45
case 0x65: // { "ADC", AM_ZP }, // 65
case 0xA4: // { "LDY", AM_ZP }, // A4
case 0xA5: // { "LDA", AM_ZP }, // A5
case 0xA6: // { "LDX", AM_ZP }, // A6
case 0xC4: // { "CPY", AM_ZP }, // C4
case 0xC5: // { "CMP", AM_ZP }, // C5
case 0xE4: // { "CPX", AM_ZP }, // E4
case 0xE5: // { "SBC", AM_ZP }, // E5
#ifdef ILLEGALS
case 0xA7: // { "LAX", AM_ZP }, // A7 (illegal)
#endif
R_BADDR_ZP;
break;
case 0x0D: // { "ORA", AM_ABS }, // 0D
case 0x2C: // { "BIT", AM_ABS }, // 2C
case 0x2D: // { "AND", AM_ABS }, // 2D
case 0x4D: // { "EOR", AM_ABS }, // 4D
case 0x6D: // { "ADC", AM_ABS }, // 6D
case 0xAC: // { "LDY", AM_ABS }, // AC
case 0xAD: // { "LDA", AM_ABS }, // AD
case 0xAE: // { "LDX", AM_ABS }, // AE
case 0xCC: // { "CPY", AM_ABS }, // CC
case 0xCD: // { "CMP", AM_ABS }, // CD
case 0xEC: // { "CPX", AM_ABS }, // EC
case 0xED: // { "SBC", AM_ABS }, // ED
#ifdef ILLEGALS
case 0xAF: // { "LAX", AM_ABS }, // AF (illegal)
#endif
R_BADDR_ABS;
break;
case 0x15: // { "ORA", AM_ZPX }, // 15
case 0x35: // { "AND", AM_ZPX }, // 35
case 0x55: // { "EOR", AM_ZPX }, // 55
case 0x75: // { "ADC", AM_ZPX }, // 75
case 0xB4: // { "LDY", AM_ZPX }, // B4
case 0xB5: // { "LDA", AM_ZPX }, // B5
case 0xD5: // { "CMP", AM_ZPX }, // D5
case 0xF5: // { "SBC", AM_ZPX }, // F5
R_BADDR_ZPX;
break;
case 0x19: // { "ORA", AM_ABY }, // 19
case 0x39: // { "AND", AM_ABY }, // 39
case 0x59: // { "EOR", AM_ABY }, // 59
case 0x79: // { "ADC", AM_ABY }, // 79
case 0xB9: // { "LDA", AM_ABY }, // B9
case 0xBE: // { "LDX", AM_ABY }, // BE
case 0xD9: // { "CMP", AM_ABY }, // D9
case 0xF9: // { "SBC", AM_ABY }, // F9
#ifdef ILLEGALS
case 0xBF: // { "LAX", AM_ABY }, // BF (illegal)
#endif
R_BADDR_ABY;
break;
case 0x1D: // { "ORA", AM_ABX }, // 1D
case 0x3D: // { "AND", AM_ABX }, // 3D
case 0x5D: // { "EOR", AM_ABX }, // 5D
case 0x7D: // { "ADC", AM_ABX }, // 7D
case 0xBC: // { "LDY", AM_ABX }, // BC
case 0xBD: // { "LDA", AM_ABX }, // BD
case 0xDD: // { "CMP", AM_ABX }, // DD
case 0xFD: // { "SBC", AM_ABX }, // FD
R_BADDR_ABX;
break;
case 0xB6: // { "LDX", AM_ZPY }, // B6
#ifdef ILLEGALS
case 0xB7: // { "LAX", AM_ZPY }, // B7 (illegal)
#endif
R_BADDR_ZPY;
break;
case 0x6C: // { "JMP", AM_IND }, // 6C
raddr = (cpu->read( cpu, cpu->calcpc+2 )<<8)|cpu->read( cpu, cpu->calcpc+1 );
rlen = 2;
break;
case 0x81: // { "STA", AM_ZIX }, // 81
#ifdef ILLEGALS
case 0x83: // { "SAX", AM_ZIX }, // 83 (illegal)
#endif
W_BADDR_ZIX;
break;
case 0x84: // { "STY", AM_ZP }, // 84
case 0x85: // { "STA", AM_ZP }, // 85
case 0x86: // { "STX", AM_ZP }, // 86
#ifdef ILLEGALS
case 0x87: // { "SAX", AM_ZP }, // 87 (illegal)
#endif
W_BADDR_ZP;
break;
case 0x8C: // { "STY", AM_ABS }, // 8C
case 0x8D: // { "STA", AM_ABS }, // 8D
case 0x8E: // { "STX", AM_ABS }, // 8E
#ifdef ILLEGALS
case 0x8F: // { "SAX", AM_ABS }, // 8F (illegal)
#endif
W_BADDR_ABS;
break;
case 0x91: // { "STA", AM_ZIY }, // 91
W_BADDR_ZIY;
break;
case 0x94: // { "STY", AM_ZPX }, // 94
case 0x95: // { "STA", AM_ZPX }, // 95
W_BADDR_ZPX;
break;
case 0x96: // { "STX", AM_ZPY }, // 96
#ifdef ILLEGALS
case 0x97: // { "SAX", AM_ZPY }, // 97 (illegal)
#endif
W_BADDR_ZPY;
break;
case 0x99: // { "STA", AM_ABY }, // 99
#ifdef ILLEGALS
case 0x9F: // { "AHX", AM_ABY }, // 9F (illegal, unstable)
case 0x9B: // { "TAS", AM_ABY }, // 9B (illegal, unstable)
#endif
W_BADDR_ABY;
break;
case 0x9D: // { "STA", AM_ABX }, // 9D
W_BADDR_ABX;
break;
}
for( i=0; i<16; i++ )
{
if( ( wlen != 0 ) && ( cpu->membreakpoints[i].flags & MBPF_WRITE ) )
{
if( ( cpu->membreakpoints[i].addr >= waddr ) &&
( cpu->membreakpoints[i].addr < (waddr+wlen) ) )
{
sprintf( bpmsg, "Break on WRITE to $%04X", cpu->membreakpoints[i].addr );
return SDL_TRUE;
}
}
if( ( rlen != 0 ) && ( cpu->membreakpoints[i].flags & MBPF_READ ) )
{
if( ( cpu->membreakpoints[i].addr >= raddr ) &&
( cpu->membreakpoints[i].addr < (raddr+rlen) ) )
{
sprintf( bpmsg, "Break on READ from $%04X", cpu->membreakpoints[i].addr );
return SDL_TRUE;
}
}
if( cpu->membreakpoints[i].flags & MBPF_CHANGE )
{
if( cpu->membreakpoints[i].lastval != cpu->read( cpu, cpu->membreakpoints[i].addr ) )
{
cpu->membreakpoints[i].lastval = cpu->read( cpu, cpu->membreakpoints[i].addr );
sprintf( bpmsg, "Break after $%04X changed", cpu->membreakpoints[i].addr );
return SDL_TRUE;
}
}
}
}
}
switch( cpu->calcop )
{
case 0x00: // { "BRK", AM_IMP }, // 00
case 0x1E: // { "ASL", AM_ABX }, // 1E
case 0x3E: // { "ROL", AM_ABX }, // 3E
case 0x5E: // { "LSR", AM_ABX }, // 5E
case 0x7E: // { "ROR", AM_ABX }, // 7E
case 0xDE: // { "DEC", AM_ABX }, // DE
case 0xFE: // { "INC", AM_ABX }, // FE
case 0xDF: // { "DCP", AM_ABX }, // DF (illegal)
case 0xDB: // { "DCP", AM_ZPY }, // DB (illegal)
case 0xFF: // { "ISC", AM_ABX }, // FF (illegal)
case 0xFB: // { "ISC", AM_ABY }, // FB (illegal)
case 0x3F: // { "RLA", AM_ABX }, // 3F (illegal)
case 0x3B: // { "RLA", AM_ABY }, // 3B (illegal)
case 0x7F: // { "RRA", AM_ABX }, // 7F (illegal)
case 0x7B: // { "RRA", AM_ABY }, // 7B (illegal)
case 0x1F: // { "SLO", AM_ABX }, // 1F (illegal)
case 0x1B: // { "SLO", AM_ABY }, // 1B (illegal)
cpu->icycles = 7;
break;
case 0x01: // { "ORA", AM_ZIX }, // 01
case 0x0E: // { "ASL", AM_ABS }, // 0E
case 0x16: // { "ASL", AM_ZPX }, // 16
case 0x20: // { "JSR", AM_ABS }, // 20
case 0x21: // { "AND", AM_ZIX }, // 21
case 0x2E: // { "ROL", AM_ABS }, // 2E
case 0x36: // { "ROL", AM_ZPX }, // 36
case 0x40: // { "RTI", AM_IMP }, // 40
case 0x41: // { "EOR", AM_ZIX }, // 41
case 0x4E: // { "LSR", AM_ABS }, // 4E
case 0x56: // { "LSR", AM_ZPX }, // 56
case 0x60: // { "RTS", AM_IMP }, // 60
case 0x61: // { "ADC", AM_ZIX }, // 61
case 0x6E: // { "ROR", AM_ABS }, // 6E
case 0x76: // { "ROR", AM_ZPX }, // 76
case 0x81: // { "STA", AM_ZIX }, // 81
case 0x91: // { "STA", AM_ZIY }, // 91
case 0xA1: // { "LDA", AM_ZIX }, // A1
case 0xC1: // { "CMP", AM_ZIX }, // C1
case 0xD6: // { "DEC", AM_ZPX }, // D6
case 0xE1: // { "SBC", AM_ZIX }, // E1
case 0xEE: // { "INC", AM_ABS }, // EE
case 0xF6: // { "INC", AM_ZPX }, // F6
case 0xCE: // { "DEC", AM_ABS }, // CE
case 0x83: // { "SAX", AM_ZIX }, // 83 (illegal)
case 0x93: // { "AHX", AM_ZIY }, // 93 (illegal, unstable)
case 0xD7: // { "DCP", AM_ZPX }, // D7 (illegal)
case 0xCF: // { "DCP", AM_ABS }, // CF (illegal)
case 0xF7: // { "ISC", AM_ZPX }, // F7 (illegal)
case 0xEF: // { "ISC", AM_ABS }, // EF (illegal)
case 0xA3: // { "LAX", AM_ABY }, // A3 (illegal)
case 0x37: // { "RLA", AM_ZPX }, // 37 (illegal)
case 0x2F: // { "RLA", AM_ABS }, // 2F (illegal)
case 0x77: // { "RRA", AM_ZPX }, // 77 (illegal)
case 0x6F: // { "RRA", AM_ABS }, // 6F (illegal)
case 0x17: // { "SLO", AM_ZPX }, // 17 (illegal)
case 0x0F: // { "SLO", AM_ABS }, // 0F (illegal)
cpu->icycles = 6;
break;
case 0x05: // { "ORA", AM_ZP }, // 05
case 0x08: // { "PHP", AM_IMP }, // 08
case 0x24: // { "BIT", AM_ZP }, // 24
case 0x25: // { "AND", AM_ZP }, // 25
case 0x45: // { "EOR", AM_ZP }, // 45
case 0x48: // { "PHA", AM_IMP }, // 48
case 0x4C: // { "JMP", AM_ABS }, // 4C
case 0x65: // { "ADC", AM_ZP }, // 65
case 0x84: // { "STY", AM_ZP }, // 84
case 0x85: // { "STA", AM_ZP }, // 85
case 0x86: // { "STX", AM_ZP }, // 86
case 0xA4: // { "LDY", AM_ZP }, // A4
case 0xA5: // { "LDA", AM_ZP }, // A5
case 0xA6: // { "LDX", AM_ZP }, // A6
case 0xC4: // { "CPY", AM_ZP }, // C4
case 0xC5: // { "CMP", AM_ZP }, // C5
case 0xE4: // { "CPX", AM_ZP }, // E4
case 0xE5: // { "SBC", AM_ZP }, // E5
case 0x87: // { "SAX", AM_ZP }, // 87 (illegal)
case 0x04: // { "DOP", AM_ZP }, // 04 (illegal)
case 0x44: // { "DOP", AM_ZP }, // 44 (illegal)
case 0x64: // { "DOP", AM_ZP }, // 64 (illegal)
case 0xA7: // { "LAX", AM_ZP }, // A7 (illegal)
cpu->icycles = 3;
break;
case 0x06: // { "ASL", AM_ZP }, // 06
case 0x26: // { "ROL", AM_ZP }, // 26
case 0x46: // { "LSR", AM_ZP }, // 46
case 0x66: // { "ROR", AM_ZP }, // 66
case 0x6C: // { "JMP", AM_IND }, // 6C
case 0x99: // { "STA", AM_ABY }, // 99
case 0x9D: // { "STA", AM_ABX }, // 9D
case 0xC6: // { "DEC", AM_ZP }, // C6
case 0xE6: // { "INC", AM_ZP }, // E6
case 0x9F: // { "AHX", AM_ABY }, // 9F (illegal, unstable)
case 0xC7: // { "DCP", AM_ZP }, // C7 (illegal)
case 0xE7: // { "ISC", AM_ZP }, // E7 (illegal)
case 0x27: // { "RLA", AM_ZP }, // 27 (illegal)
case 0x67: // { "RRA", AM_ZP }, // 67 (illegal)
case 0x07: // { "SLO", AM_ZP }, // 07 (illegal)
case 0x9E: // { "SHX", AM_ABY }, // 9E (illegal, unstable)
case 0x9C: // { "SHY", AM_ABX }, // 9C (illegal, unstable)
case 0x9B: // { "TAS", AM_ABY }, // 9B (illegal, unstable)
cpu->icycles = 5;
break;
case 0x09: // { "ORA", AM_IMM }, // 09
case 0x0A: // { "ASL", AM_IMP }, // 0A
case 0x18: // { "CLC", AM_IMP }, // 18
case 0x29: // { "AND", AM_IMM }, // 29
case 0x2A: // { "ROL", AM_IMP }, // 2A
case 0x38: // { "SEC", AM_IMP }, // 38
case 0x49: // { "EOR", AM_IMM }, // 49
case 0x4A: // { "LSR", AM_IMP }, // 4A
case 0x58: // { "CLI", AM_IMP }, // 58
case 0x69: // { "ADC", AM_IMM }, // 69
case 0x6A: // { "ROR", AM_IMP }, // 6A
case 0x78: // { "SEI", AM_IMP }, // 78
case 0x88: // { "DEY", AM_IMP }, // 88
case 0x8A: // { "TXA", AM_IMP }, // 8A
case 0x98: // { "TYA", AM_IMP }, // 98
case 0x9A: // { "TXS", AM_IMP }, // 9A
case 0xA0: // { "LDY", AM_IMM }, // A0
case 0xA2: // { "LDX", AM_IMM }, // A2
case 0xA8: // { "TAY", AM_IMP }, // A8
case 0xA9: // { "LDA", AM_IMM }, // A9
case 0xAA: // { "TAX", AM_IMP }, // AA
case 0xB8: // { "CLV", AM_IMP }, // B8
case 0xBA: // { "TSX", AM_IMP }, // BA
case 0xC0: // { "CPY", AM_IMM }, // C0
case 0xC8: // { "INY", AM_IMP }, // C8
case 0xC9: // { "CMP", AM_IMM }, // C9
case 0xCA: // { "DEX", AM_IMP }, // CA
case 0xD8: // { "CLD", AM_IMP }, // D8
case 0xE0: // { "CPX", AM_IMM }, // E0
case 0xE8: // { "INX", AM_IMP }, // E8
case 0xE9: // { "SBC", AM_IMM }, // E9
case 0xEB: // { "SBC", AM_IMM }, // EB (illegal)
case 0xEA: // { "NOP", AM_IMP }, // EA
case 0xF8: // { "SED", AM_IMP }, // F8
case 0x0B: // { "ANC", AM_IMM }, // 0B (illegal)
case 0x2B: // { "ANC", AM_IMM }, // 2B (illegal)
case 0x6B: // { "ARR", AM_IMM }, // 6B (illegal)
case 0x4B: // { "ALR", AM_IMM }, // 4B (illegal)
case 0xAB: // { "LAX", AM_IMM }, // AB (illegal, unstable)
case 0xCB: // { "AXS", AM_IMM }, // CB (illegal)
case 0x80: // { "DOP", AM_IMM }, // 80 (illegal)
case 0x82: // { "DOP", AM_IMM }, // 82 (illegal)
case 0x89: // { "DOP", AM_IMM }, // 89 (illegal)
case 0xC2: // { "DOP", AM_IMM }, // C2 (illegal)
case 0xE2: // { "DOP", AM_IMM }, // E2 (illegal)
case 0x1A: // { "NOP", AM_IMP }, // 1A (illegal)
case 0x3A: // { "NOP", AM_IMP }, // 3A (illegal)
case 0x5A: // { "NOP", AM_IMP }, // 5A (illegal)
case 0x7A: // { "NOP", AM_IMP }, // 7A (illegal)
case 0xDA: // { "NOP", AM_IMP }, // DA (illegal)
case 0xFA: // { "NOP", AM_IMP }, // FA (illegal)
case 0x8B: // { "XAA", AM_IMM }, // 8B (illegal, unstable)
cpu->icycles = 2;
break;
case 0x0D: // { "ORA", AM_ABS }, // 0D
case 0x15: // { "ORA", AM_ZPX }, // 15
case 0x28: // { "PLP", AM_IMP }, // 28
case 0x2C: // { "BIT", AM_ABS }, // 2C
case 0x2D: // { "AND", AM_ABS }, // 2D
case 0x35: // { "AND", AM_ZPX }, // 35
case 0x4D: // { "EOR", AM_ABS }, // 4D
case 0x55: // { "EOR", AM_ZPX }, // 55
case 0x6D: // { "ADC", AM_ABS }, // 6D
case 0x75: // { "ADC", AM_ZPX }, // 75
case 0x68: // { "PLA", AM_IMP }, // 68
case 0x8C: // { "STY", AM_ABS }, // 8C
case 0x8D: // { "STA", AM_ABS }, // 8D
case 0x8E: // { "STX", AM_ABS }, // 8E
case 0x94: // { "STY", AM_ZPX }, // 94
case 0x95: // { "STA", AM_ZPX }, // 95
case 0x96: // { "STX", AM_ZPY }, // 96
case 0xAC: // { "LDY", AM_ABS }, // AC
case 0xAD: // { "LDA", AM_ABS }, // AD
case 0xAE: // { "LDX", AM_ABS }, // AE
case 0xB4: // { "LDY", AM_ZPX }, // B4
case 0xB5: // { "LDA", AM_ZPX }, // B5
case 0xB6: // { "LDX", AM_ZPY }, // B6
case 0xCC: // { "CPY", AM_ABS }, // CC
case 0xCD: // { "CMP", AM_ABS }, // CD
case 0xD5: // { "CMP", AM_ZPX }, // D5
case 0xEC: // { "CPX", AM_ABS }, // EC
case 0xED: // { "SBC", AM_ABS }, // ED
case 0xF5: // { "SBC", AM_ZPX }, // F5
case 0x97: // { "SAX", AM_ZPY }, // 97 (illegal)
case 0x8F: // { "SAX", AM_ABS }, // 8F (illegal)
case 0x14: // { "DOP", AM_ZPX }, // 14 (illegal)
case 0x34: // { "DOP", AM_ZPX }, // 34 (illegal)
case 0x54: // { "DOP", AM_ZPX }, // 54 (illegal)
case 0x74: // { "DOP", AM_ZPX }, // 74 (illegal)
case 0xD4: // { "DOP", AM_ZPX }, // D4 (illegal)
case 0xF4: // { "DOP", AM_ZPX }, // F4 (illegal)
case 0xB7: // { "LAX", AM_ZPY }, // B7 (illegal)
case 0xAF: // { "LAX", AM_ABS }, // AF (illegal)
case 0x0C: // { "TOP", AM_ABS }, // 0C (illegal)
cpu->icycles = 4;
break;
case 0xC3: // { "DCP", AM_ZIX }, // C3 (illegal)
case 0xD3: // { "DCP", AM_ZIY }, // D3 (illegal)
case 0xE3: // { "ISC", AM_ZIY }, // E3 (illegal)
case 0xF3: // { "ISC", AM_ZIY }, // F3 (illegal)
case 0x23: // { "RLA", AM_ZIX }, // 23 (illegal)
case 0x33: // { "RLA", AM_ZIY }, // 33 (illegal)
case 0x63: // { "RRA", AM_ZIX }, // 63 (illegal)
case 0x73: // { "RRA", AM_ZIY }, // 73 (illegal)
case 0x03: // { "SLO", AM_ZIX }, // 03 (illegal)
case 0x13: // { "SLO", AM_ZIY }, // 13 (illegal)
cpu->icycles = 8;
break;
case 0x10: // { "BPL", AM_REL }, // 10
IBRANCH( !cpu->f_n );
break;
case 0x11: // { "ORA", AM_ZIY }, // 11
case 0x31: // { "AND", AM_ZIY }, // 31
case 0x51: // { "EOR", AM_ZIY }, // 51
case 0x71: // { "ADC", AM_ZIY }, // 71
case 0xB1: // { "LDA", AM_ZIY }, // B1
case 0xD1: // { "CMP", AM_ZIY }, // D1
case 0xF1: // { "SBC", AM_ZIY }, // F1
case 0xB3: // { "LAX", AM_ZIY }, // B3 (illegal)
baddr = cpu->read( cpu, cpu->calcpc+1 );
baddr = ((cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ));
cpu->icycles = 5;
cpu->baddr = baddr+cpu->y;
if( CPAGECHECK ) cpu->icycles++;
break;
case 0xBB: // { "LAS", AM_ZIY }, // BB
baddr = cpu->read( cpu, cpu->calcpc+1 );
baddr = ((cpu->read( cpu, baddr+1 )<<8) | cpu->read( cpu, baddr ));
cpu->icycles = 4;
cpu->baddr = baddr+cpu->y;
if( CPAGECHECK ) cpu->icycles++;
break;
case 0x19: // { "ORA", AM_ABY }, // 19
case 0x39: // { "AND", AM_ABY }, // 39
case 0x59: // { "EOR", AM_ABY }, // 59
case 0x79: // { "ADC", AM_ABY }, // 79
case 0xB9: // { "LDA", AM_ABY }, // B9
case 0xBE: // { "LDX", AM_ABY }, // BE
case 0xD9: // { "CMP", AM_ABY }, // D9
case 0xF9: // { "SBC", AM_ABY }, // F9
case 0xBF: // { "LAX", AM_ABY }, // BF (illegal)
NBADDR_ABS;
cpu->icycles = 4;
cpu->baddr = baddr+cpu->y;
if( CPAGECHECK ) cpu->icycles++;
break;
case 0x1D: // { "ORA", AM_ABX }, // 1D
case 0x3D: // { "AND", AM_ABX }, // 3D
case 0x5D: // { "EOR", AM_ABX }, // 5D
case 0x7D: // { "ADC", AM_ABX }, // 7D
case 0xBC: // { "LDY", AM_ABX }, // BC
case 0xBD: // { "LDA", AM_ABX }, // BD
case 0xDD: // { "CMP", AM_ABX }, // DD
case 0xFD: // { "SBC", AM_ABX }, // FD
case 0x1C: // { "TOP", AM_ABX }, // 1C (illegal)
case 0x3C: // { "TOP", AM_ABX }, // 3C (illegal)
case 0x5C: // { "TOP", AM_ABX }, // 5C (illegal)
case 0x7C: // { "TOP", AM_ABX }, // 7C (illegal)
case 0xDC: // { "TOP", AM_ABX }, // DC (illegal)
case 0xFC: // { "TOP", AM_ABX }, // FC (illegal)
NBADDR_ABS;
cpu->icycles = 4;
cpu->baddr = baddr+cpu->x;
if( CPAGECHECK ) cpu->icycles++;
break;
case 0x30: // { "BMI", AM_REL }, // 30
IBRANCH( cpu->f_n );
break;
case 0x50: // { "BVC", AM_REL }, // 50
IBRANCH( !cpu->f_v );
break;
case 0x70: // { "BVS", AM_REL }, // 70
IBRANCH( cpu->f_v );
break;
case 0x90: // { "BCC", AM_REL }, // 90
IBRANCH( !cpu->f_c );
break;
case 0xB0: // { "BCS", AM_REL }, // B0
IBRANCH( cpu->f_c );
break;
case 0xD0: // { "BNE", AM_REL }, // D0
IBRANCH( !cpu->f_z );
break;
case 0xF0: // { "BEQ", AM_REL }, // F0
IBRANCH( cpu->f_z );
break;
default:
cpu->icycles = 6;
break;
}
cpu->icycles += extra;
return SDL_FALSE;
}
// Execute one 6502 instruction
SDL_bool m6502_inst( struct m6502 *cpu )
{
unsigned char v;
unsigned short r, t, baddr;
// Make sure you call set_icycles before this routine!
cpu->cycles += cpu->icycles;
if( cpu->calcint > 0 )
{
PUSHW( cpu->pc );
PUSHB( MAKEFLAGSBC );
cpu->f_d = 0;
if( cpu->calcint == 2 )
{
cpu->nmi = SDL_FALSE;
} else {
cpu->f_i = 1;