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cebix |
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/* |
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* cpu.cpp - 6510 CPU emulation |
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* |
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* SIDPlayer (C) Copyright 1996-2000 Christian Bauer |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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#include "sys.h" |
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#include "mem.h" |
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#include "sid.h" |
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#define DEBUG 0 |
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#include "debug.h" |
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// Memory access functions |
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typedef uint32 (*mem_read_func)(uint32, cycle_t); |
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typedef void (*mem_write_func)(uint32, uint32, cycle_t, bool); |
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static mem_read_func mem_read_table[256]; // Table of read/write functions for 256 pages |
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static mem_write_func mem_write_table[256]; |
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// Memory access function prototypes |
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static uint32 ram_read(uint32 adr, cycle_t now); |
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static void ram_write(uint32 adr, uint32 byte, cycle_t now, bool rmw); |
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static void cia_write(uint32 adr, uint32 byte, cycle_t now, bool rmw); |
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/* |
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* Init CPU emulation |
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*/ |
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static void set_memory_funcs(uint16 from, uint16 to, mem_read_func r, mem_write_func w) |
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{ |
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for (int page = (from >> 8); page <= (to >> 8); page++) { |
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mem_read_table[page] = r; |
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mem_write_table[page] = w; |
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} |
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} |
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void CPUInit(void) |
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{ |
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// Set up memory access tables |
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set_memory_funcs(0x0000, 0xffff, ram_read, ram_write); |
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set_memory_funcs(0xd400, 0xd7ff, sid_read, sid_write); |
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set_memory_funcs(0xdc00, 0xdcff, ram_read, cia_write); |
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} |
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/* |
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* Exit CPU emulation |
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*/ |
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void CPUExit(void) |
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{ |
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} |
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/* |
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* Memory access functions |
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*/ |
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static uint32 ram_read(uint32 adr, cycle_t now) |
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{ |
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return ram[adr]; |
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} |
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static void ram_write(uint32 adr, uint32 byte, cycle_t now, bool rmw) |
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{ |
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ram[adr] = byte; |
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} |
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static void cia_write(uint32 adr, uint32 byte, cycle_t now, bool rmw) |
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{ |
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if (adr == 0xdc04) |
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cia_tl_write(byte); |
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else if (adr == 0xdc05) |
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cia_th_write(byte); |
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else |
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ram[adr] = byte; |
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} |
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/* |
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* CPU emulation loop |
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*/ |
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void CPUExecute(uint16 startadr, uint8 init_ra, uint8 init_rx, uint8 init_ry, cycle_t max_cycles) |
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{ |
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// 6510 registers |
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register uint8 a = init_ra, x = init_rx, y = init_ry; |
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register uint8 n_flag = 0, z_flag = 0; |
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uint8 sp = 0xff, pflags = 0; |
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// Program counter |
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register uint8 *pc; |
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// Temporary address storage |
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uint16 adr; |
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// Phi 2 cycle counter |
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register cycle_t current_cycle = 0; |
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// Flag: last branch instruction delays IRQ/NMI by 1 cycle (unused) |
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bool branch_delays_int = false; |
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#define RA a |
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#define RX x |
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#define RY y |
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#define RSP sp |
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#define RPC (pc - ram) |
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#define N_FLAG n_flag |
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#define Z_FLAG z_flag |
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#define PFLAGS pflags |
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#define ADR adr |
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#define read_byte(adr) \ |
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mem_read_table[(adr) >> 8](adr, current_cycle) |
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#define read_zp(adr) \ |
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ram[adr] |
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#define write_byte(adr, byte) \ |
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mem_write_table[(adr) >> 8](adr, byte, current_cycle, false) |
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#define write_byte_rmw(adr, byte) \ |
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mem_write_table[(adr) >> 8](adr, byte, current_cycle, true) |
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#define write_zp(adr, byte) \ |
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ram[adr] = (byte) |
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#define read_idle(adr) |
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#define read_idle_zp(adr) |
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#define read_idle_stack(sp) |
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#define read_opcode \ |
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(*pc) |
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#define read_idle_opcode |
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#define push_byte(byte) \ |
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{ \ |
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if (sp == 0) \ |
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quit = true; \ |
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(ram + 0x100)[sp--] = (byte); \ |
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} |
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#define pop_byte \ |
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(sp == 0xff ? (quit = true, 0) : (ram + 0x100)[++sp]) |
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#define jump(adr) \ |
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pc = ram + (adr) |
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#define inc_pc \ |
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pc++ |
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#define next_cycle \ |
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current_cycle++ |
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#include "cpu_macros.h" |
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// Jump to specified start address |
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jump(startadr); |
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// Main loop: execute opcodes until stack under-/overflow, RTI, illegal opcode, or max_cycles reached |
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bool quit = false; |
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while (current_cycle < max_cycles && !quit) { |
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// Fetch opcode |
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uint8 opcode = read_opcode; inc_pc; next_cycle; |
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// Execute opcode |
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switch (opcode) { |
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#include "cpu_opcodes.h" |
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case 0xf2: |
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default: |
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illegal_op: quit = true; |
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break; |
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} |
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} |
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} |
