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979 lines
29 KiB
C
979 lines
29 KiB
C
// http://rubbermallet.org/fake6502.c
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/* Fake6502 CPU emulator core v1.1 *******************
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* (c)2011 Mike Chambers (miker00lz@gmail.com) *
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*****************************************************
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* v1.1 - Small bugfix in BIT opcode, but it was the *
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* difference between a few games in my NES *
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* emulator working and being broken! *
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* I went through the rest carefully again *
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* after fixing it just to make sure I didn't *
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* have any other typos! (Dec. 17, 2011) *
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* *
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* v1.0 - First release (Nov. 24, 2011) *
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*****************************************************
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* LICENSE: This source code is released into the *
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* public domain, but if you use it please do give *
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* credit. I put a lot of effort into writing this! *
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* *
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*****************************************************
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* Fake6502 is a MOS Technology 6502 CPU emulation *
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* engine in C. It was written as part of a Nintendo *
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* Entertainment System emulator I've been writing. *
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* *
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* It has been pretty well-tested in the NES emu, *
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* and the clock-cycle timing in particular has been *
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* VERY thoroughly checked out. It matches with the *
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* real 6502 processor 100%. *
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* *
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* A couple important things to know about are two *
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* defines in the code. One is "UNDOCUMENTED" which, *
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* when defined, allows Fake6502 to compile with *
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* full support for the more predictable *
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* undocumented instructions of the 6502. If it is *
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* undefined, undocumented opcodes just act as NOPs. *
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* *
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* The other define is "NES_CPU", which causes the *
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* code to compile without support for binary-coded *
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* decimal (BCD) support for the ADC and SBC *
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* opcodes. The Ricoh 2A03 CPU in the NES does not *
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* support BCD, but is otherwise identical to the *
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* standard MOS 6502. (Note that this define is *
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* enabled in this file if you haven't changed it *
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* yourself. If you're not emulating a NES, you *
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* should comment it out.) *
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* *
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* If you do discover an error in timing accuracy, *
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* or operation in general please e-mail me at the *
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* address above so that I can fix it. Thank you! *
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* *
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*****************************************************
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* Usage: *
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* *
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* Fake6502 requires you to provide two external *
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* functions: *
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* *
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* uint8_t read6502(uint16_t address) *
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* void write6502(uint16_t address, uint8_t value) *
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* *
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* You may optionally pass Fake6502 the pointer to a *
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* function which you want to be called after every *
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* emulated instruction. This function should be a *
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* void with no parameters expected to be passed to *
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* it. *
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* *
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* This can be very useful. For example, in a NES *
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* emulator, you check the number of clock ticks *
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* that have passed so you can know when to handle *
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* APU events. *
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* *
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* To pass Fake6502 this pointer, use the *
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* hookexternal(void *funcptr) function provided. *
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* *
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* To disable the hook later, pass NULL to it. *
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*****************************************************
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* Useful functions in this emulator: *
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* *
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* void reset6502() *
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* - Call this once before you begin execution. *
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* *
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* void exec6502(uint32_t tickcount) *
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* - Execute 6502 code up to the next specified *
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* count of clock ticks. *
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* *
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* void step6502() *
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* - Execute a single instrution. *
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* *
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* void irq6502() *
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* - Trigger a hardware IRQ in the 6502 core. *
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* *
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* void nmi6502() *
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* - Trigger an NMI in the 6502 core. *
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* *
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* void hookexternal(void *funcptr) *
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* - Pass a pointer to a void function taking no *
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* parameters. This will cause Fake6502 to call *
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* that function once after each emulated *
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* instruction. *
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* *
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*****************************************************
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* Useful variables in this emulator: *
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* *
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* uint32_t clockticks6502 *
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* - A running total of the emulated cycle count. *
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* *
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* uint32_t instructions *
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* - A running total of the total emulated *
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* instruction count. This is not related to *
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* clock cycle timing. *
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* *
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*****************************************************/
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#include <stdio.h>
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#include <stdint.h>
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//6502 defines
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#define UNDOCUMENTED //when this is defined, undocumented opcodes are handled.
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//otherwise, they're simply treated as NOPs.
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#undef NES_CPU //when this is defined, the binary-coded decimal (BCD)
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//status flag is not honored by ADC and SBC. the 2A03
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//CPU in the Nintendo Entertainment System does not
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//support BCD operation.
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#define FLAG_CARRY 0x01
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#define FLAG_ZERO 0x02
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#define FLAG_INTERRUPT 0x04
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#define FLAG_DECIMAL 0x08
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#define FLAG_BREAK 0x10
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#define FLAG_CONSTANT 0x20
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#define FLAG_OVERFLOW 0x40
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#define FLAG_SIGN 0x80
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#define BASE_STACK 0x100
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#define saveaccum(n) a = (uint8_t)((n) & 0x00FF)
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//flag modifier macros
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#define setcarry() status |= FLAG_CARRY
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#define clearcarry() status &= (~FLAG_CARRY)
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#define setzero() status |= FLAG_ZERO
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#define clearzero() status &= (~FLAG_ZERO)
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#define setinterrupt() status |= FLAG_INTERRUPT
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#define clearinterrupt() status &= (~FLAG_INTERRUPT)
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#define setdecimal() status |= FLAG_DECIMAL
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#define cleardecimal() status &= (~FLAG_DECIMAL)
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#define setoverflow() status |= FLAG_OVERFLOW
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#define clearoverflow() status &= (~FLAG_OVERFLOW)
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#define setsign() status |= FLAG_SIGN
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#define clearsign() status &= (~FLAG_SIGN)
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//flag calculation macros
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#define zerocalc(n) {\
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if ((n) & 0x00FF) clearzero();\
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else setzero();\
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}
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#define signcalc(n) {\
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if ((n) & 0x0080) setsign();\
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else clearsign();\
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}
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#define carrycalc(n) {\
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if ((n) & 0xFF00) setcarry();\
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else clearcarry();\
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}
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#define overflowcalc(n, m, o) { /* n = result, m = accumulator, o = memory */ \
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if (((n) ^ (uint16_t)(m)) & ((n) ^ (o)) & 0x0080) setoverflow();\
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else clearoverflow();\
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}
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//6502 CPU registers
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uint16_t pc;
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uint8_t sp, a, x, y, status;
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//helper variables
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uint32_t instructions = 0; //keep track of total instructions executed
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uint32_t clockticks6502 = 0, clockgoal6502 = 0;
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uint16_t oldpc, ea, reladdr, value, result;
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uint8_t opcode, oldstatus;
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//externally supplied functions
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extern uint8_t read6502(uint16_t address);
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extern void write6502(uint16_t address, uint8_t value);
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//a few general functions used by various other functions
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void push16(uint16_t pushval) {
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write6502(BASE_STACK + sp, (pushval >> 8) & 0xFF);
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write6502(BASE_STACK + ((sp - 1) & 0xFF), pushval & 0xFF);
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sp -= 2;
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}
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void push8(uint8_t pushval) {
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write6502(BASE_STACK + sp--, pushval);
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}
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uint16_t pull16() {
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uint16_t temp16;
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temp16 = read6502(BASE_STACK + ((sp + 1) & 0xFF)) | ((uint16_t)read6502(BASE_STACK + ((sp + 2) & 0xFF)) << 8);
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sp += 2;
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return(temp16);
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}
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uint8_t pull8() {
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return (read6502(BASE_STACK + ++sp));
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}
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void reset6502() {
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pc = (uint16_t)read6502(0xFFFC) | ((uint16_t)read6502(0xFFFD) << 8);
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a = 0;
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x = 0;
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y = 0;
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sp = 0xFD;
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status |= FLAG_CONSTANT;
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}
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static void (*addrtable[256])();
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static void (*optable[256])();
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uint8_t penaltyop, penaltyaddr;
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//addressing mode functions, calculates effective addresses
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static void imp() { //implied
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}
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static void acc() { //accumulator
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}
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static void imm() { //immediate
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ea = pc++;
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}
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static void zp() { //zero-page
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ea = (uint16_t)read6502((uint16_t)pc++);
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}
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static void zpx() { //zero-page,X
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ea = ((uint16_t)read6502((uint16_t)pc++) + (uint16_t)x) & 0xFF; //zero-page wraparound
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}
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static void zpy() { //zero-page,Y
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ea = ((uint16_t)read6502((uint16_t)pc++) + (uint16_t)y) & 0xFF; //zero-page wraparound
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}
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static void rel() { //relative for branch ops (8-bit immediate value, sign-extended)
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reladdr = (uint16_t)read6502(pc++);
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if (reladdr & 0x80) reladdr |= 0xFF00;
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}
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static void abso() { //absolute
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ea = (uint16_t)read6502(pc) | ((uint16_t)read6502(pc+1) << 8);
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pc += 2;
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}
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static void absx() { //absolute,X
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uint16_t startpage;
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ea = ((uint16_t)read6502(pc) | ((uint16_t)read6502(pc+1) << 8));
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startpage = ea & 0xFF00;
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ea += (uint16_t)x;
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if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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penaltyaddr = 1;
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}
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pc += 2;
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}
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static void absy() { //absolute,Y
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uint16_t startpage;
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ea = ((uint16_t)read6502(pc) | ((uint16_t)read6502(pc+1) << 8));
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startpage = ea & 0xFF00;
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ea += (uint16_t)y;
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if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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penaltyaddr = 1;
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}
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pc += 2;
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}
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static void ind() { //indirect
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uint16_t eahelp, eahelp2;
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eahelp = (uint16_t)read6502(pc) | (uint16_t)((uint16_t)read6502(pc+1) << 8);
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eahelp2 = (eahelp & 0xFF00) | ((eahelp + 1) & 0x00FF); //replicate 6502 page-boundary wraparound bug
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ea = (uint16_t)read6502(eahelp) | ((uint16_t)read6502(eahelp2) << 8);
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pc += 2;
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}
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static void indx() { // (indirect,X)
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uint16_t eahelp;
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eahelp = (uint16_t)(((uint16_t)read6502(pc++) + (uint16_t)x) & 0xFF); //zero-page wraparound for table pointer
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ea = (uint16_t)read6502(eahelp & 0x00FF) | ((uint16_t)read6502((eahelp+1) & 0x00FF) << 8);
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}
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static void indy() { // (indirect),Y
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uint16_t eahelp, eahelp2, startpage;
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eahelp = (uint16_t)read6502(pc++);
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eahelp2 = (eahelp & 0xFF00) | ((eahelp + 1) & 0x00FF); //zero-page wraparound
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ea = (uint16_t)read6502(eahelp) | ((uint16_t)read6502(eahelp2) << 8);
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startpage = ea & 0xFF00;
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ea += (uint16_t)y;
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if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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penaltyaddr = 1;
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}
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}
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static uint16_t getvalue() {
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if (addrtable[opcode] == acc) return((uint16_t)a);
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else return((uint16_t)read6502(ea));
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}
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static uint16_t getvalue16() {
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return((uint16_t)read6502(ea) | ((uint16_t)read6502(ea+1) << 8));
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}
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static void putvalue(uint16_t saveval) {
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if (addrtable[opcode] == acc) a = (uint8_t)(saveval & 0x00FF);
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else write6502(ea, (saveval & 0x00FF));
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}
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//instruction handler functions
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static void adc() {
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penaltyop = 1;
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value = getvalue();
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result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);
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carrycalc(result);
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zerocalc(result);
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overflowcalc(result, a, value);
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signcalc(result);
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#ifndef NES_CPU
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if (status & FLAG_DECIMAL) {
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clearcarry();
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if ((a & 0x0F) > 0x09) {
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a += 0x06;
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}
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if ((a & 0xF0) > 0x90) {
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a += 0x60;
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setcarry();
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}
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clockticks6502++;
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}
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#endif
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saveaccum(result);
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}
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static void and() {
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penaltyop = 1;
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value = getvalue();
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result = (uint16_t)a & value;
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zerocalc(result);
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signcalc(result);
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saveaccum(result);
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}
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static void asl() {
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value = getvalue();
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result = value << 1;
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carrycalc(result);
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zerocalc(result);
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signcalc(result);
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putvalue(result);
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}
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static void bcc() {
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if ((status & FLAG_CARRY) == 0) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void bcs() {
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if ((status & FLAG_CARRY) == FLAG_CARRY) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void beq() {
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if ((status & FLAG_ZERO) == FLAG_ZERO) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void bit() {
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value = getvalue();
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result = (uint16_t)a & value;
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zerocalc(result);
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status = (status & 0x3F) | (uint8_t)(value & 0xC0);
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}
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static void bmi() {
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if ((status & FLAG_SIGN) == FLAG_SIGN) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void bne() {
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if ((status & FLAG_ZERO) == 0) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void bpl() {
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if ((status & FLAG_SIGN) == 0) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void brk() {
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pc++;
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push16(pc); //push next instruction address onto stack
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push8(status | FLAG_BREAK); //push CPU status to stack
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setinterrupt(); //set interrupt flag
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pc = (uint16_t)read6502(0xFFFE) | ((uint16_t)read6502(0xFFFF) << 8);
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}
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static void bvc() {
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if ((status & FLAG_OVERFLOW) == 0) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void bvs() {
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if ((status & FLAG_OVERFLOW) == FLAG_OVERFLOW) {
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oldpc = pc;
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pc += reladdr;
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if ((oldpc & 0xFF00) != (pc & 0xFF00)) clockticks6502 += 2; //check if jump crossed a page boundary
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else clockticks6502++;
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}
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}
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static void clc() {
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clearcarry();
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}
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static void cld() {
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cleardecimal();
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}
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static void cli() {
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clearinterrupt();
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}
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static void clv() {
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clearoverflow();
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}
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static void cmp() {
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penaltyop = 1;
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value = getvalue();
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result = (uint16_t)a - value;
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if (a >= (uint8_t)(value & 0x00FF)) setcarry();
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else clearcarry();
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if (a == (uint8_t)(value & 0x00FF)) setzero();
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else clearzero();
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signcalc(result);
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}
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static void cpx() {
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value = getvalue();
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result = (uint16_t)x - value;
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if (x >= (uint8_t)(value & 0x00FF)) setcarry();
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else clearcarry();
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if (x == (uint8_t)(value & 0x00FF)) setzero();
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else clearzero();
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signcalc(result);
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}
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static void cpy() {
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value = getvalue();
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result = (uint16_t)y - value;
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if (y >= (uint8_t)(value & 0x00FF)) setcarry();
|
|
else clearcarry();
|
|
if (y == (uint8_t)(value & 0x00FF)) setzero();
|
|
else clearzero();
|
|
signcalc(result);
|
|
}
|
|
|
|
static void dec() {
|
|
value = getvalue();
|
|
result = value - 1;
|
|
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
putvalue(result);
|
|
}
|
|
|
|
static void dex() {
|
|
x--;
|
|
|
|
zerocalc(x);
|
|
signcalc(x);
|
|
}
|
|
|
|
static void dey() {
|
|
y--;
|
|
|
|
zerocalc(y);
|
|
signcalc(y);
|
|
}
|
|
|
|
static void eor() {
|
|
penaltyop = 1;
|
|
value = getvalue();
|
|
result = (uint16_t)a ^ value;
|
|
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
saveaccum(result);
|
|
}
|
|
|
|
static void inc() {
|
|
value = getvalue();
|
|
result = value + 1;
|
|
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
putvalue(result);
|
|
}
|
|
|
|
static void inx() {
|
|
x++;
|
|
|
|
zerocalc(x);
|
|
signcalc(x);
|
|
}
|
|
|
|
static void iny() {
|
|
y++;
|
|
|
|
zerocalc(y);
|
|
signcalc(y);
|
|
}
|
|
|
|
static void jmp() {
|
|
pc = ea;
|
|
}
|
|
|
|
static void jsr() {
|
|
push16(pc - 1);
|
|
pc = ea;
|
|
}
|
|
|
|
static void lda() {
|
|
penaltyop = 1;
|
|
value = getvalue();
|
|
a = (uint8_t)(value & 0x00FF);
|
|
|
|
zerocalc(a);
|
|
signcalc(a);
|
|
}
|
|
|
|
static void ldx() {
|
|
penaltyop = 1;
|
|
value = getvalue();
|
|
x = (uint8_t)(value & 0x00FF);
|
|
|
|
zerocalc(x);
|
|
signcalc(x);
|
|
}
|
|
|
|
static void ldy() {
|
|
penaltyop = 1;
|
|
value = getvalue();
|
|
y = (uint8_t)(value & 0x00FF);
|
|
|
|
zerocalc(y);
|
|
signcalc(y);
|
|
}
|
|
|
|
static void lsr() {
|
|
value = getvalue();
|
|
result = value >> 1;
|
|
|
|
if (value & 1) setcarry();
|
|
else clearcarry();
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
putvalue(result);
|
|
}
|
|
|
|
static void nop() {
|
|
switch (opcode) {
|
|
case 0x1C:
|
|
case 0x3C:
|
|
case 0x5C:
|
|
case 0x7C:
|
|
case 0xDC:
|
|
case 0xFC:
|
|
penaltyop = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void ora() {
|
|
penaltyop = 1;
|
|
value = getvalue();
|
|
result = (uint16_t)a | value;
|
|
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
saveaccum(result);
|
|
}
|
|
|
|
static void pha() {
|
|
push8(a);
|
|
}
|
|
|
|
static void php() {
|
|
push8(status | FLAG_BREAK);
|
|
}
|
|
|
|
static void pla() {
|
|
a = pull8();
|
|
|
|
zerocalc(a);
|
|
signcalc(a);
|
|
}
|
|
|
|
static void plp() {
|
|
status = pull8() | FLAG_CONSTANT;
|
|
}
|
|
|
|
static void rol() {
|
|
value = getvalue();
|
|
result = (value << 1) | (status & FLAG_CARRY);
|
|
|
|
carrycalc(result);
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
putvalue(result);
|
|
}
|
|
|
|
static void ror() {
|
|
value = getvalue();
|
|
result = (value >> 1) | ((status & FLAG_CARRY) << 7);
|
|
|
|
if (value & 1) setcarry();
|
|
else clearcarry();
|
|
zerocalc(result);
|
|
signcalc(result);
|
|
|
|
putvalue(result);
|
|
}
|
|
|
|
static void rti() {
|
|
status = pull8();
|
|
value = pull16();
|
|
pc = value;
|
|
}
|
|
|
|
static void rts() {
|
|
value = pull16();
|
|
pc = value + 1;
|
|
}
|
|
|
|
static void sbc() {
|
|
penaltyop = 1;
|
|
value = getvalue() ^ 0x00FF;
|
|
result = (uint16_t)a + value + (uint16_t)(status & FLAG_CARRY);
|
|
|
|
carrycalc(result);
|
|
zerocalc(result);
|
|
overflowcalc(result, a, value);
|
|
signcalc(result);
|
|
|
|
#ifndef NES_CPU
|
|
if (status & FLAG_DECIMAL) {
|
|
clearcarry();
|
|
|
|
a -= 0x66;
|
|
if ((a & 0x0F) > 0x09) {
|
|
a += 0x06;
|
|
}
|
|
if ((a & 0xF0) > 0x90) {
|
|
a += 0x60;
|
|
setcarry();
|
|
}
|
|
|
|
clockticks6502++;
|
|
}
|
|
#endif
|
|
|
|
saveaccum(result);
|
|
}
|
|
|
|
static void sec() {
|
|
setcarry();
|
|
}
|
|
|
|
static void sed() {
|
|
setdecimal();
|
|
}
|
|
|
|
static void sei() {
|
|
setinterrupt();
|
|
}
|
|
|
|
static void sta() {
|
|
putvalue(a);
|
|
}
|
|
|
|
static void stx() {
|
|
putvalue(x);
|
|
}
|
|
|
|
static void sty() {
|
|
putvalue(y);
|
|
}
|
|
|
|
static void tax() {
|
|
x = a;
|
|
|
|
zerocalc(x);
|
|
signcalc(x);
|
|
}
|
|
|
|
static void tay() {
|
|
y = a;
|
|
|
|
zerocalc(y);
|
|
signcalc(y);
|
|
}
|
|
|
|
static void tsx() {
|
|
x = sp;
|
|
|
|
zerocalc(x);
|
|
signcalc(x);
|
|
}
|
|
|
|
static void txa() {
|
|
a = x;
|
|
|
|
zerocalc(a);
|
|
signcalc(a);
|
|
}
|
|
|
|
static void txs() {
|
|
sp = x;
|
|
}
|
|
|
|
static void tya() {
|
|
a = y;
|
|
|
|
zerocalc(a);
|
|
signcalc(a);
|
|
}
|
|
|
|
//undocumented instructions
|
|
#ifdef UNDOCUMENTED
|
|
static void lax() {
|
|
lda();
|
|
ldx();
|
|
}
|
|
|
|
static void sax() {
|
|
sta();
|
|
stx();
|
|
putvalue(a & x);
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void dcp() {
|
|
dec();
|
|
cmp();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void isb() {
|
|
inc();
|
|
sbc();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void slo() {
|
|
asl();
|
|
ora();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void rla() {
|
|
rol();
|
|
and();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void sre() {
|
|
lsr();
|
|
eor();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
|
|
static void rra() {
|
|
ror();
|
|
adc();
|
|
if (penaltyop && penaltyaddr) clockticks6502--;
|
|
}
|
|
#else
|
|
#define lax nop
|
|
#define sax nop
|
|
#define dcp nop
|
|
#define isb nop
|
|
#define slo nop
|
|
#define rla nop
|
|
#define sre nop
|
|
#define rra nop
|
|
#endif
|
|
|
|
|
|
static void (*addrtable[256])() = {
|
|
/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
|
|
/* 0 */ imp, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, abso, abso, abso, abso, /* 0 */
|
|
/* 1 */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx, /* 1 */
|
|
/* 2 */ abso, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, abso, abso, abso, abso, /* 2 */
|
|
/* 3 */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx, /* 3 */
|
|
/* 4 */ imp, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, abso, abso, abso, abso, /* 4 */
|
|
/* 5 */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx, /* 5 */
|
|
/* 6 */ imp, indx, imp, indx, zp, zp, zp, zp, imp, imm, acc, imm, ind, abso, abso, abso, /* 6 */
|
|
/* 7 */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx, /* 7 */
|
|
/* 8 */ imm, indx, imm, indx, zp, zp, zp, zp, imp, imm, imp, imm, abso, abso, abso, abso, /* 8 */
|
|
/* 9 */ rel, indy, imp, indy, zpx, zpx, zpy, zpy, imp, absy, imp, absy, absx, absx, absy, absy, /* 9 */
|
|
/* A */ imm, indx, imm, indx, zp, zp, zp, zp, imp, imm, imp, imm, abso, abso, abso, abso, /* A */
|
|
/* B */ rel, indy, imp, indy, zpx, zpx, zpy, zpy, imp, absy, imp, absy, absx, absx, absy, absy, /* B */
|
|
/* C */ imm, indx, imm, indx, zp, zp, zp, zp, imp, imm, imp, imm, abso, abso, abso, abso, /* C */
|
|
/* D */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx, /* D */
|
|
/* E */ imm, indx, imm, indx, zp, zp, zp, zp, imp, imm, imp, imm, abso, abso, abso, abso, /* E */
|
|
/* F */ rel, indy, imp, indy, zpx, zpx, zpx, zpx, imp, absy, imp, absy, absx, absx, absx, absx /* F */
|
|
};
|
|
|
|
static void (*optable[256])() = {
|
|
/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
|
|
/* 0 */ brk, ora, nop, slo, nop, ora, asl, slo, php, ora, asl, nop, nop, ora, asl, slo, /* 0 */
|
|
/* 1 */ bpl, ora, nop, slo, nop, ora, asl, slo, clc, ora, nop, slo, nop, ora, asl, slo, /* 1 */
|
|
/* 2 */ jsr, and, nop, rla, bit, and, rol, rla, plp, and, rol, nop, bit, and, rol, rla, /* 2 */
|
|
/* 3 */ bmi, and, nop, rla, nop, and, rol, rla, sec, and, nop, rla, nop, and, rol, rla, /* 3 */
|
|
/* 4 */ rti, eor, nop, sre, nop, eor, lsr, sre, pha, eor, lsr, nop, jmp, eor, lsr, sre, /* 4 */
|
|
/* 5 */ bvc, eor, nop, sre, nop, eor, lsr, sre, cli, eor, nop, sre, nop, eor, lsr, sre, /* 5 */
|
|
/* 6 */ rts, adc, nop, rra, nop, adc, ror, rra, pla, adc, ror, nop, jmp, adc, ror, rra, /* 6 */
|
|
/* 7 */ bvs, adc, nop, rra, nop, adc, ror, rra, sei, adc, nop, rra, nop, adc, ror, rra, /* 7 */
|
|
/* 8 */ nop, sta, nop, sax, sty, sta, stx, sax, dey, nop, txa, nop, sty, sta, stx, sax, /* 8 */
|
|
/* 9 */ bcc, sta, nop, nop, sty, sta, stx, sax, tya, sta, txs, nop, nop, sta, nop, nop, /* 9 */
|
|
/* A */ ldy, lda, ldx, lax, ldy, lda, ldx, lax, tay, lda, tax, nop, ldy, lda, ldx, lax, /* A */
|
|
/* B */ bcs, lda, nop, lax, ldy, lda, ldx, lax, clv, lda, tsx, lax, ldy, lda, ldx, lax, /* B */
|
|
/* C */ cpy, cmp, nop, dcp, cpy, cmp, dec, dcp, iny, cmp, dex, nop, cpy, cmp, dec, dcp, /* C */
|
|
/* D */ bne, cmp, nop, dcp, nop, cmp, dec, dcp, cld, cmp, nop, dcp, nop, cmp, dec, dcp, /* D */
|
|
/* E */ cpx, sbc, nop, isb, cpx, sbc, inc, isb, inx, sbc, nop, sbc, cpx, sbc, inc, isb, /* E */
|
|
/* F */ beq, sbc, nop, isb, nop, sbc, inc, isb, sed, sbc, nop, isb, nop, sbc, inc, isb /* F */
|
|
};
|
|
|
|
static const uint32_t ticktable[256] = {
|
|
/* | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | */
|
|
/* 0 */ 7, 6, 2, 8, 3, 3, 5, 5, 3, 2, 2, 2, 4, 4, 6, 6, /* 0 */
|
|
/* 1 */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7, /* 1 */
|
|
/* 2 */ 6, 6, 2, 8, 3, 3, 5, 5, 4, 2, 2, 2, 4, 4, 6, 6, /* 2 */
|
|
/* 3 */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7, /* 3 */
|
|
/* 4 */ 6, 6, 2, 8, 3, 3, 5, 5, 3, 2, 2, 2, 3, 4, 6, 6, /* 4 */
|
|
/* 5 */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7, /* 5 */
|
|
/* 6 */ 6, 6, 2, 8, 3, 3, 5, 5, 4, 2, 2, 2, 5, 4, 6, 6, /* 6 */
|
|
/* 7 */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7, /* 7 */
|
|
/* 8 */ 2, 6, 2, 6, 3, 3, 3, 3, 2, 2, 2, 2, 4, 4, 4, 4, /* 8 */
|
|
/* 9 */ 2, 6, 2, 6, 4, 4, 4, 4, 2, 5, 2, 5, 5, 5, 5, 5, /* 9 */
|
|
/* A */ 2, 6, 2, 6, 3, 3, 3, 3, 2, 2, 2, 2, 4, 4, 4, 4, /* A */
|
|
/* B */ 2, 5, 2, 5, 4, 4, 4, 4, 2, 4, 2, 4, 4, 4, 4, 4, /* B */
|
|
/* C */ 2, 6, 2, 8, 3, 3, 5, 5, 2, 2, 2, 2, 4, 4, 6, 6, /* C */
|
|
/* D */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7, /* D */
|
|
/* E */ 2, 6, 2, 8, 3, 3, 5, 5, 2, 2, 2, 2, 4, 4, 6, 6, /* E */
|
|
/* F */ 2, 5, 2, 8, 4, 4, 6, 6, 2, 4, 2, 7, 4, 4, 7, 7 /* F */
|
|
};
|
|
|
|
|
|
void nmi6502() {
|
|
push16(pc);
|
|
push8(status);
|
|
status |= FLAG_INTERRUPT;
|
|
pc = (uint16_t)read6502(0xFFFA) | ((uint16_t)read6502(0xFFFB) << 8);
|
|
}
|
|
|
|
void irq6502() {
|
|
push16(pc);
|
|
push8(status);
|
|
status |= FLAG_INTERRUPT;
|
|
pc = (uint16_t)read6502(0xFFFE) | ((uint16_t)read6502(0xFFFF) << 8);
|
|
}
|
|
|
|
uint8_t callexternal = 0;
|
|
void (*loopexternal)();
|
|
|
|
void exec6502(uint32_t tickcount) {
|
|
clockgoal6502 += tickcount;
|
|
|
|
while (clockticks6502 < clockgoal6502) {
|
|
opcode = read6502(pc++);
|
|
status |= FLAG_CONSTANT;
|
|
|
|
penaltyop = 0;
|
|
penaltyaddr = 0;
|
|
|
|
(*addrtable[opcode])();
|
|
(*optable[opcode])();
|
|
clockticks6502 += ticktable[opcode];
|
|
if (penaltyop && penaltyaddr) clockticks6502++;
|
|
|
|
instructions++;
|
|
|
|
if (callexternal) (*loopexternal)();
|
|
}
|
|
|
|
}
|
|
|
|
void step6502() {
|
|
opcode = read6502(pc++);
|
|
status |= FLAG_CONSTANT;
|
|
|
|
penaltyop = 0;
|
|
penaltyaddr = 0;
|
|
|
|
(*addrtable[opcode])();
|
|
(*optable[opcode])();
|
|
clockticks6502 += ticktable[opcode];
|
|
if (penaltyop && penaltyaddr) clockticks6502++;
|
|
clockgoal6502 = clockticks6502;
|
|
|
|
instructions++;
|
|
|
|
if (callexternal) (*loopexternal)();
|
|
}
|
|
|
|
void hookexternal(void *funcptr) {
|
|
if (funcptr != (void *)NULL) {
|
|
loopexternal = funcptr;
|
|
callexternal = 1;
|
|
} else callexternal = 0;
|
|
}
|