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/*
6502 - 6502 emulation
Copyright (C) 2025 Ian Cowburn <ianc@noddybox.co.uk>
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; either version 3 of the License, or
(at your option) any later version.
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, see <http://www.gnu.org/licenses/>
-------------------------------------------------------------------------
*/
#ifndef C6502_H
#define C6502_H
#include <stdio.h>
/* ---------------------------------------- TYPES
*/
/* Large unsigned type
*/
typedef unsigned long C6502Val;
/* 8-bit type. The emulation will exit with code 2 if this isn't 8 bits.
*/
typedef unsigned char C6502Byte;
/* 8-bit signed type. The emulation will exit with code 2 if this isn't 8 bits.
We assume this is 2's complemnt.
*/
typedef signed char C6502Relative;
/* 16-bit type. The emulation will exit with code 2 if this isn't 16 bits.
*/
typedef unsigned short C6502Word;
/* The processor
*/
struct C6502Private;
typedef struct
{
C6502Word PC;
C6502Byte A;
C6502Byte X;
C6502Byte Y;
C6502Byte SP;
C6502Byte SR;
struct C6502Private *priv;
} C6502;
/* Interfaces used to handle memory
*/
typedef C6502Byte (*C6502ReadMemory)(C6502 *cpu, C6502Word address);
typedef void (*C6502WriteMemory)(C6502 *cpu,
C6502Word address,
C6502Byte value);
/* Callback. Callback should return TRUE for processing to continue.
*/
typedef int (*C6502Callback)(C6502 *cpu, C6502Val current_cycles);
/* Callback reasons
eC6502_Instruction Called before the initial fetch for an instruction
(called just to once no matter how many bytes the
instruction is made up of).
eC6502_BRK Called when a BRK is executed.
eC6502_JAM Called when the CPU hits an opcode that jams the CPU.
eC6502_RTI Called when the RTI instruction is executed
*/
typedef enum
{
eC6502_Instruction,
eC6502_BRK,
eC6502_JAM,
eC6502_RTI,
eC6502_NO_CALLBACK
} C6502CallbackReason;
/* Defines cycle timers
*/
typedef enum
{
C6502_TIMER_1,
C6502_TIMER_2,
C6502_TIMER_3,
C6502_NO_TIMERS
} C6502Timer;
/* Flags in the F register
*/
typedef enum
{
eC6502_Carry =0x01,
eC6502_Neg =0x02,
eC6502_PV =0x04,
eC6502_Hidden3 =0x08,
eC6502_HalfCarry =0x10,
eC6502_Hidden5 =0x20,
eC6502_Zero =0x40,
eC6502_Sign =0x80
} C6502FlagRegister;
/* Disassembly label -- only useful if ENABLE_DISASSEMBLER is set.
Labels are stored as an array, where a NULL in the label field marks
the end of the list.
*/
typedef struct
{
C6502Word address;
const char *label;
} C6502Label;
/* ---------------------------------------- INTERFACES
*/
/* Initialises the processor.
*/
#ifdef ENABLE_ARRAY_MEMORY
C6502 *C6502Init(void);
#else
C6502 *C6502Init(C6502ReadMemory read_memory,
C6502WriteMemory write_memory,
C6502ReadMemory read_for_disassem);
#endif
/* Resets the processor.
*/
void C6502Reset(C6502 *cpu);
/* Lodge a callback to be invoked after special events. Returns FALSE
if the callback couldn't be lodged (there is a max of 10 callbacks per
reason).
*/
int C6502LodgeCallback(C6502 *cpu,
C6502CallbackReason reason,
C6502Callback callback);
/* Remove a callback. Does nothing if reason was not lodged with
C6502LodgeCallback()
*/
void C6502RemoveCallback(C6502 *cpu,
C6502CallbackReason reason,
C6502Callback callback);
/* Cause an interrupt before the next opcode.
*/
void C6502Interrupt(C6502 *cpu);
/* Cause an NMI
*/
void C6502NMI(C6502 *cpu);
/* Execute a single instruction. Returns FALSE if any callback returned
FALSE.
*/
int C6502SingleStep(C6502 *cpu);
/* Executes until a callback returns FALSE (never returns otherwise)
*/
void C6502Exec(C6502 *cpu);
/* Manipulate the cylce count of the C6502
*/
C6502Val C6502Cycles(C6502 *cpu);
void C6502ResetCycles(C6502 *cpu, C6502Val cycles);
/* Timers that count in cycle counts
*/
C6502Val C6502GetTimer(C6502 *cpu, C6502Timer timer);
void C6502SetTimer(C6502 *cpu, C6502Timer timer, C6502Val cycles);
/* Set address to label mappings for the disassembler
*/
void C6502SetLabels(C6502Label labels[]);
/* Simple disassembly of memory accessed through read_for_disassem, or
C6502_MEMORY as appropriate. addr is updated on exit.
*/
const char *C6502Disassemble(C6502 *cpu, C6502Word *addr);
/* Allows the CPU state to be saved/loaded from a stream
*/
void C6502SaveSnapshot(C6502 *cpu, FILE *fp);
void C6502LoadSnapshot(C6502 *cpu, FILE *fp);
#endif
/* END OF FILE */
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