1122 lines
23 KiB
C
1122 lines
23 KiB
C
// NES 6502 CPU emulator run function
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#if 0
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/* Define these macros in the source file before #including this file.
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- Parameters might be expressions, so they are best evaluated only once,
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though they NEVER have side-effects, so multiple evaluation is OK.
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- Output parameters might be a multiple-assignment expression like "a=x",
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so they must NOT be parenthesized.
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- Except where noted, time() and related functions will NOT work
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correctly inside a macro. TIME() is always correct, and FLUSH_TIME() and
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CACHE_TIME() allow the time changing functions to work.
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- Macros "returning" void may use a {} statement block. */
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// 0 <= addr <= 0xFFFF + page_size
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// time functions can be used
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int READ_MEM( addr_t );
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void WRITE_MEM( addr_t, int data );
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// 0 <= READ_MEM() <= 0xFF
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// 0 <= addr <= 0x1FF
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int READ_LOW( addr_t );
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void WRITE_LOW( addr_t, int data );
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// 0 <= READ_LOW() <= 0xFF
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// Often-used instructions attempt these before using a normal memory access.
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// Optional; defaults to READ_MEM() and WRITE_MEM()
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bool CAN_READ_FAST( addr_t ); // if true, uses result of READ_FAST
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void READ_FAST( addr_t, int& out ); // ALWAYS called BEFORE CAN_READ_FAST
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bool CAN_WRITE_FAST( addr_t ); // if true, uses WRITE_FAST instead of WRITE_MEM
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void WRITE_FAST( addr_t, int data );
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// Used by instructions most often used to access the NES PPU (LDA abs and BIT abs).
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// Optional; defaults to READ_MEM.
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void READ_PPU( addr_t, int& out );
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// 0 <= out <= 0xFF
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// The following can be used within macros:
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// Current time
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time_t TIME();
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// Allows use of time functions
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void FLUSH_TIME();
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// Must be used before end of macro if FLUSH_TIME() was used earlier
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void CACHE_TIME();
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// Configuration (optional; commented behavior if defined)
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// Emulates dummy reads for indexed instructions
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#define NES_CPU_DUMMY_READS 1
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// Optimizes as if map_code( 0, 0x10000 + cpu_padding, FLAT_MEM ) is always in effect
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#define FLAT_MEM my_mem_array
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// Expanded just before beginning of code, to help debugger
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#define CPU_BEGIN void my_run_cpu() {
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#endif
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/* Copyright (C) 2003-2008 Shay Green. This module is free software; you
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can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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module is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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details. You should have received a copy of the GNU Lesser General Public
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License along with this module; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
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// Allows MWCW debugger to step through code properly
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#ifdef CPU_BEGIN
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CPU_BEGIN
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#endif
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// Time
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#define TIME() (s_time + s.base)
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#define FLUSH_TIME() {s.time = s_time - time_offset;}
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#define CACHE_TIME() {s_time = s.time + time_offset;}
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// Defaults
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#ifndef CAN_WRITE_FAST
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#define CAN_WRITE_FAST( addr ) 0
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#define WRITE_FAST( addr, data )
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#endif
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#ifndef CAN_READ_FAST
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#define CAN_READ_FAST( addr ) 0
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#define READ_FAST( addr, out )
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#endif
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#ifndef READ_PPU
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#define READ_PPU( addr, out )\
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{\
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FLUSH_TIME();\
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out = READ_MEM( addr );\
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CACHE_TIME();\
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}
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#endif
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#define READ_STACK READ_LOW
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#define WRITE_STACK WRITE_LOW
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// Dummy reads
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#if NES_CPU_DUMMY_READS
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// TODO: optimize time handling
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#define DUMMY_READ( addr, idx ) \
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if ( (addr & 0xFF) < idx )\
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{\
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int const time_offset = 1;\
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FLUSH_TIME();\
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READ_MEM( (addr - 0x100) );\
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CACHE_TIME();\
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}
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#else
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#define DUMMY_READ( addr, idx )
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#endif
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// Code
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#ifdef FLAT_MEM
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#define CODE_PAGE( addr ) (FLAT_MEM)
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#define CODE_OFFSET( addr ) (addr)
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#else
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#define CODE_PAGE( addr ) (s.code_map [NES_CPU_PAGE( addr )])
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#define CODE_OFFSET( addr ) NES_CPU_OFFSET( addr )
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#endif
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#define READ_CODE( addr ) (CODE_PAGE( addr ) [CODE_OFFSET( addr )])
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// Stack
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#define SET_SP( v ) (sp = ((v) + 1) | 0x100)
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#define GET_SP() ((sp - 1) & 0xFF)
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#define SP( o ) ((sp + (o - (o>0)*0x100)) | 0x100)
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// Truncation
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#define BYTE( n ) ((BOOST::uint8_t ) (n)) /* (unsigned) n & 0xFF */
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#define SBYTE( n ) ((BOOST::int8_t ) (n)) /* (BYTE( n ) ^ 0x80) - 0x80 */
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#define WORD( n ) ((BOOST::uint16_t) (n)) /* (unsigned) n & 0xFFFF */
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// Flags with hex value for clarity when used as mask.
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// Stored in indicated variable during emulation.
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int const n80 = 0x80; // nz
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int const v40 = 0x40; // flags
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int const r20 = 0x20;
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int const b10 = 0x10;
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int const d08 = 0x08; // flags
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int const i04 = 0x04; // flags
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int const z02 = 0x02; // nz
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int const c01 = 0x01; // c
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#define IS_NEG (nz & 0x8080)
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#define GET_FLAGS( out ) \
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{\
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out = flags & (v40 | d08 | i04);\
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out += ((nz >> 8) | nz) & n80;\
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out += c >> 8 & c01;\
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if ( !BYTE( nz ) )\
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out += z02;\
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}
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#define SET_FLAGS( in ) \
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{\
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flags = in & (v40 | d08 | i04);\
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c = nz = in << 8;\
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nz += ~in & z02;\
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}
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{
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int const time_offset = 0;
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// Local state
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Nes_Cpu::cpu_state_t s;
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#ifdef FLAT_MEM
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s.base = CPU.cpu_state_.base;
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#else
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s = CPU.cpu_state_;
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#endif
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CPU.cpu_state = &s;
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int s_time = CPU.cpu_state_.time; // helps even on x86
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// Registers
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int pc = CPU.r.pc;
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int a = CPU.r.a;
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int x = CPU.r.x;
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int y = CPU.r.y;
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int sp;
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SET_SP( CPU.r.sp );
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// Flags
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int flags;
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int c; // carry set if (c & 0x100) != 0
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int nz; // Z set if (nz & 0xFF) == 0, N set if (nz & 0x8080) != 0
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{
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int temp = CPU.r.flags;
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SET_FLAGS( temp );
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}
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loop:
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// Check all values
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check( (unsigned) sp - 0x100 < 0x100 );
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check( (unsigned) pc < 0x10000 );
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check( (unsigned) a < 0x100 );
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check( (unsigned) x < 0x100 );
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check( (unsigned) y < 0x100 );
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// Read instruction
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byte const* instr = CODE_PAGE( pc );
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int opcode;
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if ( CODE_OFFSET(~0) == ~0 )
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{
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opcode = instr [pc];
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pc++;
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instr += pc;
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}
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else
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{
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instr += CODE_OFFSET( pc );
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opcode = *instr++;
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pc++;
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}
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// local to function in case it helps optimizer
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static byte const clock_table [256] =
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{// 0 1 2 3 4 5 6 7 8 9 A B C D E F
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0,6,2,8,3,3,5,5,3,2,2,2,4,4,6,6,// 0
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 1
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6,6,0,8,3,3,5,5,4,2,2,2,4,4,6,6,// 2
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 3
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6,6,2,8,3,3,5,5,3,2,2,2,3,4,6,6,// 4
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 5
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6,6,2,8,3,3,5,5,4,2,2,2,5,4,6,6,// 6
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 7
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2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,// 8
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2,6,2,6,4,4,4,4,2,5,2,5,5,5,5,5,// 9
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2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,// A
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2,5,2,5,4,4,4,4,2,4,2,4,4,4,4,4,// B
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2,6,2,8,3,3,5,5,2,2,2,2,4,4,6,6,// C
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// D
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2,6,2,8,3,3,5,5,2,2,2,2,4,4,6,6,// E
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2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7 // F
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}; // 0x00 was 7 and 0x22 was 2
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// Update time
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if ( s_time >= 0 )
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goto out_of_time;
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#ifdef CPU_INSTR_HOOK
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{ CPU_INSTR_HOOK( (pc-1), (&instr [-1]), a, x, y, GET_SP(), TIME() ); }
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#endif
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s_time += clock_table [opcode];
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int data;
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data = *instr;
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switch ( opcode )
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{
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// Macros
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#define GET_MSB() (instr [1])
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#define ADD_PAGE( out ) (pc++, out = data + 0x100 * GET_MSB())
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#define GET_ADDR() GET_LE16( instr )
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#define PAGE_PENALTY( lsb ) s_time += (lsb) >> 8;
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#define INC_DEC( reg, n ) reg = BYTE( nz = reg + n ); goto loop;
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#define IND_Y( cross, out ) {\
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int temp = READ_LOW( data ) + y;\
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out = temp + 0x100 * READ_LOW( BYTE( data + 1 ) );\
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cross( temp );\
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}
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#define IND_X( out ) {\
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int temp = data + x;\
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out = 0x100 * READ_LOW( BYTE( temp + 1 ) ) + READ_LOW( BYTE( temp ) );\
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}
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#define ARITH_ADDR_MODES( op )\
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case op - 0x04: /* (ind,x) */\
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IND_X( data )\
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goto ptr##op;\
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case op + 0x0C: /* (ind),y */\
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IND_Y( PAGE_PENALTY, data )\
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goto ptr##op;\
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case op + 0x10: /* zp,X */\
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data = BYTE( data + x );\
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case op + 0x00: /* zp */\
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data = READ_LOW( data );\
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goto imm##op;\
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case op + 0x14: /* abs,Y */\
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data += y;\
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goto ind##op;\
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case op + 0x18: /* abs,X */\
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data += x;\
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ind##op:\
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PAGE_PENALTY( data );\
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case op + 0x08: /* abs */\
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ADD_PAGE( data );\
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ptr##op:\
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FLUSH_TIME();\
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data = READ_MEM( data );\
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CACHE_TIME();\
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case op + 0x04: /* imm */\
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imm##op:
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// TODO: more efficient way to handle negative branch that wraps PC around
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#define BRANCH( cond )\
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{\
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++pc;\
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if ( !(cond) ) goto loop;\
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s_time++;\
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int offset = SBYTE( data );\
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s_time += (BYTE(pc) + offset) >> 8 & 1;\
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pc = WORD( pc + offset );\
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goto loop;\
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}
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// Often-Used
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case 0xB5: // LDA zp,x
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a = nz = READ_LOW( BYTE( data + x ) );
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pc++;
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goto loop;
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case 0xA5: // LDA zp
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a = nz = READ_LOW( data );
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pc++;
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goto loop;
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case 0xD0: // BNE
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BRANCH( BYTE( nz ) );
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case 0x20: { // JSR
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int temp = pc + 1;
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pc = GET_ADDR();
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WRITE_STACK( SP( -1 ), temp >> 8 );
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sp = SP( -2 );
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WRITE_STACK( sp, temp );
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goto loop;
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}
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case 0x4C: // JMP abs
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pc = GET_ADDR();
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goto loop;
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case 0xE8: // INX
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INC_DEC( x, 1 )
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case 0x10: // BPL
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BRANCH( !IS_NEG )
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ARITH_ADDR_MODES( 0xC5 ) // CMP
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nz = a - data;
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pc++;
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c = ~nz;
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nz &= 0xFF;
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goto loop;
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case 0x30: // BMI
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BRANCH( IS_NEG )
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case 0xF0: // BEQ
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BRANCH( !BYTE( nz ) );
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case 0x95: // STA zp,x
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data = BYTE( data + x );
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case 0x85: // STA zp
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pc++;
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WRITE_LOW( data, a );
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goto loop;
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case 0xC8: // INY
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INC_DEC( y, 1 )
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case 0xA8: // TAY
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y = a;
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nz = a;
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goto loop;
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case 0x98: // TYA
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a = y;
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nz = y;
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goto loop;
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case 0xAD:{// LDA abs
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int addr = GET_ADDR();
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pc += 2;
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READ_PPU( addr, a = nz );
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goto loop;
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}
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case 0x60: // RTS
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pc = 1 + READ_STACK( sp );
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pc += 0x100 * READ_STACK( SP( 1 ) );
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sp = SP( 2 );
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goto loop;
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{
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int addr;
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case 0x8D: // STA abs
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addr = GET_ADDR();
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pc += 2;
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if ( CAN_WRITE_FAST( addr ) )
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{
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WRITE_FAST( addr, a );
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goto loop;
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}
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sta_ptr:
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FLUSH_TIME();
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WRITE_MEM( addr, a );
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CACHE_TIME();
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goto loop;
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case 0x99: // STA abs,Y
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addr = y + GET_ADDR();
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pc += 2;
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if ( CAN_WRITE_FAST( addr ) )
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{
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WRITE_FAST( addr, a );
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goto loop;
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}
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goto sta_abs_x;
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case 0x9D: // STA abs,X (slightly more common than STA abs)
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addr = x + GET_ADDR();
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pc += 2;
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if ( CAN_WRITE_FAST( addr ) )
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{
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WRITE_FAST( addr, a );
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goto loop;
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}
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DUMMY_READ( addr, x );
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sta_abs_x:
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FLUSH_TIME();
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WRITE_MEM( addr, a );
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CACHE_TIME();
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goto loop;
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case 0x91: // STA (ind),Y
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#define NO_PAGE_PENALTY( lsb )
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IND_Y( NO_PAGE_PENALTY, addr )
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pc++;
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DUMMY_READ( addr, y );
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goto sta_ptr;
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case 0x81: // STA (ind,X)
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IND_X( addr )
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pc++;
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goto sta_ptr;
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}
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case 0xA9: // LDA #imm
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pc++;
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a = data;
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nz = data;
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goto loop;
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|
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// common read instructions
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{
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int addr;
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case 0xA1: // LDA (ind,X)
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IND_X( addr )
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pc++;
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goto a_nz_read_addr;
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case 0xB1:// LDA (ind),Y
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addr = READ_LOW( data ) + y;
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PAGE_PENALTY( addr );
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addr += 0x100 * READ_LOW( BYTE( data + 1 ) );
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pc++;
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READ_FAST( addr, a = nz );
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if ( CAN_READ_FAST( addr ) )
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goto loop;
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DUMMY_READ( addr, y );
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goto a_nz_read_addr;
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case 0xB9: // LDA abs,Y
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PAGE_PENALTY( data + y );
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addr = GET_ADDR() + y;
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pc += 2;
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READ_FAST( addr, a = nz );
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if ( CAN_READ_FAST( addr ) )
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goto loop;
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goto a_nz_read_addr;
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case 0xBD: // LDA abs,X
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PAGE_PENALTY( data + x );
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addr = GET_ADDR() + x;
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pc += 2;
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READ_FAST( addr, a = nz );
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if ( CAN_READ_FAST( addr ) )
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goto loop;
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DUMMY_READ( addr, x );
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a_nz_read_addr:
|
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FLUSH_TIME();
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a = nz = READ_MEM( addr );
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CACHE_TIME();
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goto loop;
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}
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|
|
// Branch
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case 0x50: // BVC
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BRANCH( !(flags & v40) )
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|
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case 0x70: // BVS
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BRANCH( flags & v40 )
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|
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case 0xB0: // BCS
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BRANCH( c & 0x100 )
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|
|
case 0x90: // BCC
|
|
BRANCH( !(c & 0x100) )
|
|
|
|
// Load/store
|
|
|
|
case 0x94: // STY zp,x
|
|
data = BYTE( data + x );
|
|
case 0x84: // STY zp
|
|
pc++;
|
|
WRITE_LOW( data, y );
|
|
goto loop;
|
|
|
|
case 0x96: // STX zp,y
|
|
data = BYTE( data + y );
|
|
case 0x86: // STX zp
|
|
pc++;
|
|
WRITE_LOW( data, x );
|
|
goto loop;
|
|
|
|
case 0xB6: // LDX zp,y
|
|
data = BYTE( data + y );
|
|
case 0xA6: // LDX zp
|
|
data = READ_LOW( data );
|
|
case 0xA2: // LDX #imm
|
|
pc++;
|
|
x = data;
|
|
nz = data;
|
|
goto loop;
|
|
|
|
case 0xB4: // LDY zp,x
|
|
data = BYTE( data + x );
|
|
case 0xA4: // LDY zp
|
|
data = READ_LOW( data );
|
|
case 0xA0: // LDY #imm
|
|
pc++;
|
|
y = data;
|
|
nz = data;
|
|
goto loop;
|
|
|
|
case 0xBC: // LDY abs,X
|
|
data += x;
|
|
PAGE_PENALTY( data );
|
|
case 0xAC:{// LDY abs
|
|
int addr = data + 0x100 * GET_MSB();
|
|
pc += 2;
|
|
FLUSH_TIME();
|
|
y = nz = READ_MEM( addr );
|
|
CACHE_TIME();
|
|
goto loop;
|
|
}
|
|
|
|
case 0xBE: // LDX abs,y
|
|
data += y;
|
|
PAGE_PENALTY( data );
|
|
case 0xAE:{// LDX abs
|
|
int addr = data + 0x100 * GET_MSB();
|
|
pc += 2;
|
|
FLUSH_TIME();
|
|
x = nz = READ_MEM( addr );
|
|
CACHE_TIME();
|
|
goto loop;
|
|
}
|
|
|
|
{
|
|
int temp;
|
|
case 0x8C: // STY abs
|
|
temp = y;
|
|
goto store_abs;
|
|
|
|
case 0x8E: // STX abs
|
|
temp = x;
|
|
store_abs:
|
|
int addr = GET_ADDR();
|
|
pc += 2;
|
|
if ( CAN_WRITE_FAST( addr ) )
|
|
{
|
|
WRITE_FAST( addr, temp );
|
|
goto loop;
|
|
}
|
|
FLUSH_TIME();
|
|
WRITE_MEM( addr, temp );
|
|
CACHE_TIME();
|
|
goto loop;
|
|
}
|
|
|
|
// Compare
|
|
|
|
case 0xEC:{// CPX abs
|
|
int addr = GET_ADDR();
|
|
pc++;
|
|
FLUSH_TIME();
|
|
data = READ_MEM( addr );
|
|
CACHE_TIME();
|
|
goto cpx_data;
|
|
}
|
|
|
|
case 0xE4: // CPX zp
|
|
data = READ_LOW( data );
|
|
case 0xE0: // CPX #imm
|
|
cpx_data:
|
|
nz = x - data;
|
|
pc++;
|
|
c = ~nz;
|
|
nz &= 0xFF;
|
|
goto loop;
|
|
|
|
case 0xCC:{// CPY abs
|
|
int addr = GET_ADDR();
|
|
pc++;
|
|
FLUSH_TIME();
|
|
data = READ_MEM( addr );
|
|
CACHE_TIME();
|
|
goto cpy_data;
|
|
}
|
|
|
|
case 0xC4: // CPY zp
|
|
data = READ_LOW( data );
|
|
case 0xC0: // CPY #imm
|
|
cpy_data:
|
|
nz = y - data;
|
|
pc++;
|
|
c = ~nz;
|
|
nz &= 0xFF;
|
|
goto loop;
|
|
|
|
// Logical
|
|
|
|
ARITH_ADDR_MODES( 0x25 ) // AND
|
|
nz = (a &= data);
|
|
pc++;
|
|
goto loop;
|
|
|
|
ARITH_ADDR_MODES( 0x45 ) // EOR
|
|
nz = (a ^= data);
|
|
pc++;
|
|
goto loop;
|
|
|
|
ARITH_ADDR_MODES( 0x05 ) // ORA
|
|
nz = (a |= data);
|
|
pc++;
|
|
goto loop;
|
|
|
|
case 0x2C:{// BIT abs
|
|
int addr = GET_ADDR();
|
|
pc += 2;
|
|
READ_PPU( addr, nz );
|
|
flags = (flags & ~v40) + (nz & v40);
|
|
if ( a & nz )
|
|
goto loop;
|
|
nz <<= 8; // result must be zero, even if N bit is set
|
|
goto loop;
|
|
}
|
|
|
|
case 0x24: // BIT zp
|
|
nz = READ_LOW( data );
|
|
pc++;
|
|
flags = (flags & ~v40) + (nz & v40);
|
|
if ( a & nz )
|
|
goto loop; // Z should be clear, and nz must be non-zero if nz & a is
|
|
nz <<= 8; // set Z flag without affecting N flag
|
|
goto loop;
|
|
|
|
// Add/subtract
|
|
|
|
ARITH_ADDR_MODES( 0xE5 ) // SBC
|
|
case 0xEB: // unofficial equivalent
|
|
data ^= 0xFF;
|
|
goto adc_imm;
|
|
|
|
ARITH_ADDR_MODES( 0x65 ) // ADC
|
|
adc_imm: {
|
|
int carry = c >> 8 & 1;
|
|
int ov = (a ^ 0x80) + carry + SBYTE( data );
|
|
flags = (flags & ~v40) + (ov >> 2 & v40);
|
|
c = nz = a + data + carry;
|
|
pc++;
|
|
a = BYTE( nz );
|
|
goto loop;
|
|
}
|
|
|
|
// Shift/rotate
|
|
|
|
case 0x4A: // LSR A
|
|
c = 0;
|
|
case 0x6A: // ROR A
|
|
nz = c >> 1 & 0x80;
|
|
c = a << 8;
|
|
nz += a >> 1;
|
|
a = nz;
|
|
goto loop;
|
|
|
|
case 0x0A: // ASL A
|
|
nz = a << 1;
|
|
c = nz;
|
|
a = BYTE( nz );
|
|
goto loop;
|
|
|
|
case 0x2A: { // ROL A
|
|
nz = a << 1;
|
|
int temp = c >> 8 & 1;
|
|
c = nz;
|
|
nz += temp;
|
|
a = BYTE( nz );
|
|
goto loop;
|
|
}
|
|
|
|
case 0x5E: // LSR abs,X
|
|
data += x;
|
|
case 0x4E: // LSR abs
|
|
c = 0;
|
|
case 0x6E: // ROR abs
|
|
ror_abs: {
|
|
ADD_PAGE( data );
|
|
FLUSH_TIME();
|
|
int temp = READ_MEM( data );
|
|
nz = (c >> 1 & 0x80) + (temp >> 1);
|
|
c = temp << 8;
|
|
goto rotate_common;
|
|
}
|
|
|
|
case 0x3E: // ROL abs,X
|
|
data += x;
|
|
goto rol_abs;
|
|
|
|
case 0x1E: // ASL abs,X
|
|
data += x;
|
|
case 0x0E: // ASL abs
|
|
c = 0;
|
|
case 0x2E: // ROL abs
|
|
rol_abs:
|
|
ADD_PAGE( data );
|
|
nz = c >> 8 & 1;
|
|
FLUSH_TIME();
|
|
nz += (c = READ_MEM( data ) << 1);
|
|
rotate_common:
|
|
pc++;
|
|
WRITE_MEM( data, BYTE( nz ) );
|
|
CACHE_TIME();
|
|
goto loop;
|
|
|
|
case 0x7E: // ROR abs,X
|
|
data += x;
|
|
goto ror_abs;
|
|
|
|
case 0x76: // ROR zp,x
|
|
data = BYTE( data + x );
|
|
goto ror_zp;
|
|
|
|
case 0x56: // LSR zp,x
|
|
data = BYTE( data + x );
|
|
case 0x46: // LSR zp
|
|
c = 0;
|
|
case 0x66: // ROR zp
|
|
ror_zp: {
|
|
int temp = READ_LOW( data );
|
|
nz = (c >> 1 & 0x80) + (temp >> 1);
|
|
c = temp << 8;
|
|
goto write_nz_zp;
|
|
}
|
|
|
|
case 0x36: // ROL zp,x
|
|
data = BYTE( data + x );
|
|
goto rol_zp;
|
|
|
|
case 0x16: // ASL zp,x
|
|
data = BYTE( data + x );
|
|
case 0x06: // ASL zp
|
|
c = 0;
|
|
case 0x26: // ROL zp
|
|
rol_zp:
|
|
nz = c >> 8 & 1;
|
|
nz += (c = READ_LOW( data ) << 1);
|
|
goto write_nz_zp;
|
|
|
|
// Increment/decrement
|
|
|
|
case 0xCA: // DEX
|
|
INC_DEC( x, -1 )
|
|
|
|
case 0x88: // DEY
|
|
INC_DEC( y, -1 )
|
|
|
|
case 0xF6: // INC zp,x
|
|
data = BYTE( data + x );
|
|
case 0xE6: // INC zp
|
|
nz = 1;
|
|
goto add_nz_zp;
|
|
|
|
case 0xD6: // DEC zp,x
|
|
data = BYTE( data + x );
|
|
case 0xC6: // DEC zp
|
|
nz = -1;
|
|
add_nz_zp:
|
|
nz += READ_LOW( data );
|
|
write_nz_zp:
|
|
pc++;
|
|
WRITE_LOW( data, nz );
|
|
goto loop;
|
|
|
|
case 0xFE: // INC abs,x
|
|
data = x + GET_ADDR();
|
|
goto inc_ptr;
|
|
|
|
case 0xEE: // INC abs
|
|
data = GET_ADDR();
|
|
inc_ptr:
|
|
nz = 1;
|
|
goto inc_common;
|
|
|
|
case 0xDE: // DEC abs,x
|
|
data = x + GET_ADDR();
|
|
goto dec_ptr;
|
|
|
|
case 0xCE: // DEC abs
|
|
data = GET_ADDR();
|
|
dec_ptr:
|
|
nz = -1;
|
|
inc_common:
|
|
FLUSH_TIME();
|
|
pc += 2;
|
|
nz += READ_MEM( data );
|
|
WRITE_MEM( data, BYTE( nz ) );
|
|
CACHE_TIME();
|
|
goto loop;
|
|
|
|
// Transfer
|
|
|
|
case 0xAA: // TAX
|
|
x = nz = a;
|
|
goto loop;
|
|
|
|
case 0x8A: // TXA
|
|
a = nz = x;
|
|
goto loop;
|
|
|
|
case 0x9A: // TXS
|
|
SET_SP( x ); // verified (no flag change)
|
|
goto loop;
|
|
|
|
case 0xBA: // TSX
|
|
x = nz = GET_SP();
|
|
goto loop;
|
|
|
|
// Stack
|
|
|
|
case 0x48: // PHA
|
|
sp = SP( -1 );
|
|
WRITE_STACK( sp, a );
|
|
goto loop;
|
|
|
|
case 0x68: // PLA
|
|
a = nz = READ_STACK( sp );
|
|
sp = SP( 1 );
|
|
goto loop;
|
|
|
|
case 0x40:{// RTI
|
|
pc = READ_STACK( SP( 1 ) );
|
|
pc += READ_STACK( SP( 2 ) ) * 0x100;
|
|
int temp = READ_STACK( sp );
|
|
sp = SP( 3 );
|
|
data = flags;
|
|
SET_FLAGS( temp );
|
|
CPU.r.flags = flags; // update externally-visible I flag
|
|
int delta = s.base - CPU.irq_time_;
|
|
if ( delta <= 0 ) goto loop; // end_time < irq_time
|
|
if ( flags & i04 ) goto loop;
|
|
s_time += delta;
|
|
s.base = CPU.irq_time_;
|
|
goto loop;
|
|
}
|
|
|
|
case 0x28:{// PLP
|
|
int temp = READ_STACK( sp );
|
|
sp = SP( 1 );
|
|
int changed = flags ^ temp;
|
|
SET_FLAGS( temp );
|
|
if ( !(changed & i04) )
|
|
goto loop; // I flag didn't change
|
|
if ( flags & i04 )
|
|
goto handle_sei;
|
|
goto handle_cli;
|
|
}
|
|
|
|
case 0x08:{// PHP
|
|
int temp;
|
|
GET_FLAGS( temp );
|
|
sp = SP( -1 );
|
|
WRITE_STACK( sp, temp | (b10 | r20) );
|
|
goto loop;
|
|
}
|
|
|
|
case 0x6C:{// JMP (ind)
|
|
data = GET_ADDR();
|
|
byte const* page = CODE_PAGE( data );
|
|
pc = page [CODE_OFFSET( data )];
|
|
data = (data & 0xFF00) + ((data + 1) & 0xFF);
|
|
pc += page [CODE_OFFSET( data )] * 0x100;
|
|
goto loop;
|
|
}
|
|
|
|
case 0x00: // BRK
|
|
goto handle_brk;
|
|
|
|
// Flags
|
|
|
|
case 0x38: // SEC
|
|
c = 0x100;
|
|
goto loop;
|
|
|
|
case 0x18: // CLC
|
|
c = 0;
|
|
goto loop;
|
|
|
|
case 0xB8: // CLV
|
|
flags &= ~v40;
|
|
goto loop;
|
|
|
|
case 0xD8: // CLD
|
|
flags &= ~d08;
|
|
goto loop;
|
|
|
|
case 0xF8: // SED
|
|
flags |= d08;
|
|
goto loop;
|
|
|
|
case 0x58: // CLI
|
|
if ( !(flags & i04) )
|
|
goto loop;
|
|
flags &= ~i04;
|
|
handle_cli: {
|
|
//dprintf( "CLI at %d\n", TIME );
|
|
CPU.r.flags = flags; // update externally-visible I flag
|
|
int delta = s.base - CPU.irq_time_;
|
|
if ( delta <= 0 )
|
|
{
|
|
if ( TIME() < CPU.irq_time_ )
|
|
goto loop;
|
|
goto delayed_cli;
|
|
}
|
|
s.base = CPU.irq_time_;
|
|
s_time += delta;
|
|
if ( s_time < 0 )
|
|
goto loop;
|
|
|
|
if ( delta >= s_time + 1 )
|
|
{
|
|
// delayed irq until after next instruction
|
|
s.base += s_time + 1;
|
|
s_time = -1;
|
|
goto loop;
|
|
}
|
|
|
|
// TODO: implement
|
|
delayed_cli:
|
|
dprintf( "Delayed CLI not emulated\n" );
|
|
goto loop;
|
|
}
|
|
|
|
case 0x78: // SEI
|
|
if ( flags & i04 )
|
|
goto loop;
|
|
flags |= i04;
|
|
handle_sei: {
|
|
CPU.r.flags = flags; // update externally-visible I flag
|
|
int delta = s.base - CPU.end_time_;
|
|
s.base = CPU.end_time_;
|
|
s_time += delta;
|
|
if ( s_time < 0 )
|
|
goto loop;
|
|
|
|
dprintf( "Delayed SEI not emulated\n" );
|
|
goto loop;
|
|
}
|
|
|
|
// Unofficial
|
|
|
|
// SKW - skip word
|
|
case 0x1C: case 0x3C: case 0x5C: case 0x7C: case 0xDC: case 0xFC:
|
|
PAGE_PENALTY( data + x );
|
|
case 0x0C:
|
|
pc++;
|
|
// SKB - skip byte
|
|
case 0x74: case 0x04: case 0x14: case 0x34: case 0x44: case 0x54: case 0x64:
|
|
case 0x80: case 0x82: case 0x89: case 0xC2: case 0xD4: case 0xE2: case 0xF4:
|
|
pc++;
|
|
goto loop;
|
|
|
|
// NOP
|
|
case 0xEA: case 0x1A: case 0x3A: case 0x5A: case 0x7A: case 0xDA: case 0xFA:
|
|
goto loop;
|
|
|
|
case Nes_Cpu::halt_opcode: // HLT - halt processor
|
|
if ( pc-- > 0x10000 )
|
|
{
|
|
// handle wrap-around (assumes caller has put page of HLT at 0x10000)
|
|
pc = WORD( pc );
|
|
goto loop;
|
|
}
|
|
case 0x02: case 0x12: case 0x32: case 0x42: case 0x52:
|
|
case 0x62: case 0x72: case 0x92: case 0xB2: case 0xD2: case 0xF2:
|
|
goto stop;
|
|
|
|
// Unimplemented
|
|
|
|
case 0xFF: // force 256-entry jump table for optimization purposes
|
|
c |= 1; // compiler doesn't know that this won't affect anything
|
|
default:
|
|
check( (unsigned) opcode < 0x100 );
|
|
|
|
#ifdef UNIMPL_INSTR
|
|
UNIMPL_INSTR();
|
|
#endif
|
|
|
|
// At least skip over proper number of bytes instruction uses
|
|
static unsigned char const illop_lens [8] = {
|
|
0x40, 0x40, 0x40, 0x80, 0x40, 0x40, 0x80, 0xA0
|
|
};
|
|
int opcode = instr [-1];
|
|
int len = illop_lens [opcode >> 2 & 7] >> (opcode << 1 & 6) & 3;
|
|
if ( opcode == 0x9C )
|
|
len = 2;
|
|
pc += len;
|
|
CPU.error_count_++;
|
|
|
|
// Account for extra clock
|
|
if ( (opcode >> 4) == 0x0B )
|
|
{
|
|
if ( opcode == 0xB3 )
|
|
data = READ_LOW( data );
|
|
if ( opcode != 0xB7 )
|
|
PAGE_PENALTY( data + y );
|
|
}
|
|
goto loop;
|
|
}
|
|
assert( false ); // catch missing 'goto loop' or accidental 'break'
|
|
|
|
int result_;
|
|
handle_brk:
|
|
pc++;
|
|
result_ = b10 | 4;
|
|
|
|
#ifdef CPU_DONE
|
|
interrupt:
|
|
#endif
|
|
{
|
|
s_time += 7;
|
|
|
|
// Save PC and read vector
|
|
WRITE_STACK( SP( -1 ), pc >> 8 );
|
|
WRITE_STACK( SP( -2 ), pc );
|
|
pc = GET_LE16( &READ_CODE( 0xFFFA ) + (result_ & 4) );
|
|
|
|
// Save flags
|
|
int temp;
|
|
GET_FLAGS( temp );
|
|
temp |= r20 + (result_ & b10); // B flag set for BRK
|
|
sp = SP( -3 );
|
|
WRITE_STACK( sp, temp );
|
|
|
|
// Update I flag in externally-visible flags
|
|
CPU.r.flags = (flags |= i04);
|
|
|
|
// Update time
|
|
int delta = s.base - CPU.end_time_;
|
|
if ( delta >= 0 )
|
|
goto loop;
|
|
s_time += delta;
|
|
s.base = CPU.end_time_;
|
|
goto loop;
|
|
}
|
|
|
|
out_of_time:
|
|
pc--;
|
|
|
|
// Optional action that triggers interrupt or changes irq/end time
|
|
#ifdef CPU_DONE
|
|
{
|
|
CPU_DONE( result_ );
|
|
if ( result_ >= 0 )
|
|
goto interrupt;
|
|
if ( s_time < 0 )
|
|
goto loop;
|
|
}
|
|
#endif
|
|
stop:
|
|
|
|
// Flush cached state
|
|
CPU.r.pc = pc;
|
|
CPU.r.sp = GET_SP();
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|
CPU.r.a = a;
|
|
CPU.r.x = x;
|
|
CPU.r.y = y;
|
|
|
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int temp;
|
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GET_FLAGS( temp );
|
|
CPU.r.flags = temp;
|
|
|
|
CPU.cpu_state_.base = s.base;
|
|
CPU.cpu_state_.time = s_time;
|
|
CPU.cpu_state = &CPU.cpu_state_;
|
|
}
|