#include <string.h>
#include <libio.h>
#include "tools.h"
+#include "6502core.h"
+/*
+ * 6502 little endian
+ * hi bit > low bit order
+ * but gcc generates low > hi order for bit field
+ * */
struct status_reg {
- unsigned int negative :1;
- unsigned int overflow :1;
- unsigned int researved :1;
- unsigned int break_mode :1;
- unsigned int decimal :1;
- unsigned int irq_disable :1;
- unsigned int zero :1;
unsigned int carry :1;
-};
+ unsigned int zero :1;
+ unsigned int irq_disable :1;
+ unsigned int decimal :1;
+ unsigned int break_mode :1;
+ unsigned int researved :1;
+ unsigned int overflow :1;
+ unsigned int negative :1;
+} __attribute__ ((packed));
struct cpu_6502 {
unsigned char acc;
*
**/
-#define ADDR_MODE_ZP 0
-#define ADDR_MODE_ZP_X 1
-#define ADDR_MODE_ZP_Y 2
-#define ADDR_MODE_ABS 3
-#define ADDR_MODE_ABS_X 4
-#define ADDR_MODE_ABS_Y 5
-#define ADDR_MODE_IND 6
-#define ADDR_MODE_IMP 7
-#define ADDR_MODE_ACC 8
-#define ADDR_MODE_IMM 9
-#define ADDR_MODE_REL 10
-#define ADDR_MODE_INDEX_INDIR 11
-#define ADDR_MODE_INDIR_INDEX 12
-
#define N_BIT 0x80
+#define V_BIT 0x40
+
+//stack pointer base address
+#define STACK_BASE 0x100
+
+
+/* cycle check must be cleared on release */
+#define cycle_check
+
+
+#define NMI_VECTOR 0xFFFA
+#define RESET_VECTOR 0xFFFC
+#define IRQ_VECTOR 0xFFFE
struct opcode_map {
unsigned char opcode;
static struct cpu_6502 cpu_reg;
static struct opcode_map *current_inst;
+
+//exec index is the cycle consumed for execution only.
+//cpu total cycle is current_exec_index + 1 because
+//fetch cycle uses 1 cycle prior to the execution.
static int current_exec_index;
static int exec_done;
+static int intr_done;
unsigned char load_memory(unsigned short addr);
unsigned short load_addr(unsigned short addr, int cycle);
void set_cpu_data_buf(unsigned char data);
unsigned short get_cpu_addr_buf(void);
void set_cpu_addr_buf(unsigned short addr);
+int get_clock_cnt(void);
int func_ADC(void);
int func_AND(void);
/*
* load from memory in various addressing mode.
* cpu_data_buf has the output value.
+ *
+ *
* */
static int load_addr_mode(int *done) {
switch (current_inst->addr_mode) {
}
break;
+ /*
+ * Indexed zero page
+ * Wraparound is used when performing the addition so
+ * the address of the data will always be
+ * in zero page. For example, if the operand is $FF and
+ * the X register contains $01 the address
+ * of the data will be $0000, not $0100.
+ * */
case ADDR_MODE_ZP_X:
//zp indexed with x takes three cycles.
if (current_exec_index == 0) {
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short zp = get_cpu_data_buf();
+ unsigned char zp = get_cpu_data_buf();
load_memory(zp);
goto addr_mode_done;
}
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short zp = get_cpu_data_buf();
+ unsigned char zp = get_cpu_data_buf();
load_memory(zp);
goto addr_mode_done;
}
unsigned short addr = get_cpu_addr_buf();
unsigned short hi_8, added_hi_8;
- hi_8 = addr >> 8;
+ hi_8 = (addr >> 8);
addr += cpu_reg.x;
- added_hi_8 = addr >> 8;
+ added_hi_8 = (addr >> 8);
if (hi_8 == added_hi_8) {
load_memory(addr);
}
//load value in the next cycle.
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else {
}
else if (current_exec_index == 3) {
if (current_inst->cycle_aux) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
load_memory(addr);
goto addr_mode_done;
}
unsigned short addr = get_cpu_addr_buf();
unsigned short hi_8, added_hi_8;
- hi_8 = addr >> 8;
+ hi_8 = (addr >> 8);
addr += cpu_reg.y;
- added_hi_8 = addr >> 8;
+ added_hi_8 = (addr >> 8);
if (hi_8 == added_hi_8) {
load_memory(addr);
}
//load value in the next cycle.
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else {
}
else if (current_exec_index == 3) {
if (current_inst->cycle_aux) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
load_memory(addr);
goto addr_mode_done;
}
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr, 1);
+ //save addr in the temporary buffer.
+ set_cpu_data_buf(addr);
return TRUE;
}
else if (current_exec_index == 3) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr + 1, 2);
return TRUE;
}
return TRUE;
}
else if (current_exec_index == 1) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr, 1);
+ //save addr in the temporary buffer.
+ set_cpu_data_buf(addr);
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr + 1, 2);
return TRUE;
}
else if (current_exec_index == 3) {
if (current_inst->cycle_aux) {
//Add one cycle if indexing across page boundary
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
unsigned short hi_8, added_hi_8;
- hi_8 = addr >> 8;
+ hi_8 = (addr >> 8);
addr += cpu_reg.y;
- added_hi_8 = addr >> 8;
+ added_hi_8 = (addr >> 8);
if (hi_8 == added_hi_8) {
load_memory(addr);
}
//load value in the next cycle.
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
addr += cpu_reg.y;
load_memory(addr);
goto addr_mode_done;
}
else if (current_exec_index == 4) {
if (current_inst->cycle_aux) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
load_memory(addr);
goto addr_mode_done;
}
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short zp = get_cpu_data_buf();
+ unsigned char zp = get_cpu_data_buf();
store_memory(zp, data);
goto addr_mode_done;
}
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short zp = get_cpu_data_buf();
+ unsigned char zp = get_cpu_data_buf();
store_memory(zp, data);
goto addr_mode_done;
}
else if (current_exec_index == 2) {
unsigned short addr = get_cpu_addr_buf();
addr += cpu_reg.x;
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else if (current_exec_index == 3) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
store_memory(addr, data);
goto addr_mode_done;
}
else if (current_exec_index == 2) {
unsigned short addr = get_cpu_addr_buf();
addr += cpu_reg.y;
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else if (current_exec_index == 3) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
store_memory(addr, data);
goto addr_mode_done;
}
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr, 1);
+ //save addr in the temporary buffer.
+ set_cpu_data_buf(addr);
return TRUE;
}
else if (current_exec_index == 3) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr + 1, 2);
return TRUE;
}
return TRUE;
}
else if (current_exec_index == 1) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr, 1);
+ //save addr in the temporary buffer.
+ set_cpu_data_buf(addr);
return TRUE;
}
else if (current_exec_index == 2) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned char addr = get_cpu_data_buf();
load_addr(addr + 1, 2);
return TRUE;
}
else if (current_exec_index == 3) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
addr += cpu_reg.y;
- set_cpu_data_buf(addr);
+ set_cpu_addr_buf(addr);
return TRUE;
}
else if (current_exec_index == 4) {
- unsigned short addr = get_cpu_data_buf();
+ unsigned short addr = get_cpu_addr_buf();
store_memory(addr, data);
goto addr_mode_done;
}
return TRUE;
}
+/*
+ * for inc/dec/shift operation
+ * */
+static int memory_to_memory(int *do_operation, int *done) {
+ switch (current_inst->addr_mode) {
+ case ADDR_MODE_ACC:
+ case ADDR_MODE_IMP:
+ case ADDR_MODE_IMM:
+ case ADDR_MODE_REL:
+ case ADDR_MODE_ZP_Y:
+ case ADDR_MODE_ABS_Y:
+ case ADDR_MODE_INDEX_INDIR:
+ case ADDR_MODE_INDIR_INDEX:
+ //not supported.
+ return FALSE;
+
+ case ADDR_MODE_ZP:
+ //zp takes 4 cycles.
+ if (current_exec_index == 0) {
+ load_memory(cpu_reg.pc);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 1) {
+ unsigned short zp = get_cpu_data_buf();
+ load_memory(zp);
+ set_cpu_addr_buf(zp);
+ return TRUE;
+ }
+ else if (current_exec_index == 2) {
+ //arithmetic operation here!!
+ //result is set in cpu_data_buf
+ *do_operation = TRUE;
+ return TRUE;
+ }
+ else if (current_exec_index == 3) {
+ unsigned short zp = get_cpu_addr_buf();
+ unsigned short data = get_cpu_data_buf();
+ store_memory(zp, data);
+ goto mm_done;
+ }
+ break;
+
+ case ADDR_MODE_ZP_X:
+ //zp indexed with x takes 5 cycles.
+ if (current_exec_index == 0) {
+ load_memory(cpu_reg.pc);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 1) {
+ unsigned char imm = get_cpu_data_buf();
+ set_cpu_data_buf(imm + cpu_reg.x);
+ return TRUE;
+ }
+ else if (current_exec_index == 2) {
+ unsigned char zp = get_cpu_data_buf();
+ load_memory(zp);
+ set_cpu_addr_buf(zp);
+ return TRUE;
+ }
+ else if (current_exec_index == 3) {
+ //arithmetic operation here!!
+ //result is set in cpu_data_buf
+ *do_operation = TRUE;
+ return TRUE;
+ }
+ else if (current_exec_index == 4) {
+ unsigned char zp = get_cpu_addr_buf();
+ unsigned short data = get_cpu_data_buf();
+ store_memory(zp, data);
+ goto mm_done;
+ }
+ break;
+
+ case ADDR_MODE_ABS:
+ //takes 5 cycles.
+ if (current_exec_index == 0) {
+ load_addr(cpu_reg.pc, 1);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 1) {
+ load_addr(cpu_reg.pc, 2);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 2) {
+ unsigned short addr = get_cpu_addr_buf();
+ load_memory(addr);
+ return TRUE;
+ }
+ else if (current_exec_index == 3) {
+ //arithmetic operation here!!
+ //result is set in cpu_data_buf
+ *do_operation = TRUE;
+ return TRUE;
+ }
+ else if (current_exec_index == 4) {
+ unsigned short addr = get_cpu_addr_buf();
+ unsigned short data = get_cpu_data_buf();
+ store_memory(addr, data);
+ goto mm_done;
+ }
+ break;
+
+ case ADDR_MODE_ABS_X:
+ //abs indexed with x takes 6 cycles.
+ if (current_exec_index == 0) {
+ load_addr(cpu_reg.pc, 1);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 1) {
+ load_addr(cpu_reg.pc, 2);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (current_exec_index == 2) {
+ unsigned short abs = get_cpu_addr_buf();
+ set_cpu_addr_buf(abs + cpu_reg.x);
+ return TRUE;
+ }
+ else if (current_exec_index == 3) {
+ unsigned short addr = get_cpu_addr_buf();
+ load_memory(addr);
+ return TRUE;
+ }
+ else if (current_exec_index == 4) {
+ //arithmetic operation here!!
+ //result is set in cpu_data_buf
+ *do_operation = TRUE;
+ return TRUE;
+ }
+ else if (current_exec_index == 5) {
+ unsigned short addr = get_cpu_addr_buf();
+ unsigned short data = get_cpu_data_buf();
+ store_memory(addr, data);
+ goto mm_done;
+ }
+ break;
+
+ default:
+ return FALSE;
+ }
+ return FALSE;
+
+mm_done:
+ *done = TRUE;
+ return TRUE;
+}
+
/*------------- flag operation.. ---------------------*/
cpu_reg.status.negative = 0;
}
+static void set_CMP_carry(unsigned char data, unsigned char cmp) {
+ if (data >= cmp)
+ cpu_reg.status.carry = 1;
+ else
+ cpu_reg.status.carry = 0;
+}
+
+static void set_BIT_overflow(unsigned char data) {
+ if (data & V_BIT)
+ cpu_reg.status.overflow = 1;
+ else
+ cpu_reg.status.overflow = 0;
+}
+
+/*
+ * c Set if unsigned overflow; cleared if valid unsigned result.
+ * */
+static void set_ADD_carry(unsigned char d1, unsigned char d2, unsigned char d3) {
+ unsigned short d1_short = d1;
+ unsigned short d2_short = d2;
+ unsigned short d3_short = d3;
+ if (d1_short + d2_short + d3_short > 0xff)
+ cpu_reg.status.carry = 1;
+ else
+ cpu_reg.status.carry = 0;
+}
+
+/*
+ * v Set if signed overflow; cleared if valid signed result.
+ * */
+static void set_ADD_overflow(char d1, char d2, char d3) {
+ short d1_short = d1;
+ short d2_short = d2;
+ short d3_short = d3;
+ if (d1_short + d2_short + d3_short > +127 || d1_short + d2_short + d3_short < -128 )
+ cpu_reg.status.overflow = 1;
+ else
+ cpu_reg.status.overflow = 0;
+}
+
+/*
+ * c Set if unsigned borrow not required; cleared if unsigned borrow.
+ * */
+static void set_SUB_carry(unsigned char d1, unsigned char d2, unsigned char d3) {
+ unsigned short d1_short = d1;
+ unsigned short d2_short = d2;
+ unsigned short d3_short = d3;
+
+ if (d1_short >= d2_short + d3_short)
+ cpu_reg.status.carry = 1;
+ else
+ cpu_reg.status.carry = 0;
+}
+
+/*
+ * v Set if signed borrow not required; cleared if signed borrow.
+ * */
+static void set_SUB_overflow(char d1, char d2, char d3) {
+ short d1_short = d1;
+ short d2_short = d2;
+ short d3_short = d3;
+ if (d1_short >= d2_short + d3_short)
+ cpu_reg.status.overflow = 1;
+ else
+ cpu_reg.status.overflow = 0;
+}
+
+/*------------- stack operation.. ---------------------*/
+//stack operation takes two cycles.
+static void push(unsigned char data) {
+ store_memory(STACK_BASE + cpu_reg.sp, data);
+ cpu_reg.sp--;
+}
+
+static unsigned char pop(void) {
+ cpu_reg.sp++;
+ return load_memory(STACK_BASE + cpu_reg.sp);
+}
/*---------- instruction implementations. -----------------*/
+/*
+ * Add Memory to Accumulator with Carry: ADC
+ * A + M + C -> A
+ * Flags: N, V, Z, C
+ * */
int func_ADC(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char data;
+ unsigned char old_carry;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ data = get_cpu_data_buf();
+ old_carry = cpu_reg.status.carry;
+ //signed, unsigned overflow check.
+ set_ADD_carry(cpu_reg.acc, cpu_reg.status.carry, data);
+ set_ADD_overflow(cpu_reg.acc, cpu_reg.status.carry, data);
+ //add data with carry to accumurator.
+ cpu_reg.acc += data + old_carry;
+
+ // N/Z flags set.
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * AND Memory with Accumulator: AND
+ * A & M -> A
+ * Flags: N, Z
+ * */
int func_AND(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char data;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ data = get_cpu_data_buf();
+ cpu_reg.acc = cpu_reg.acc & data;
+ //N/Z flags set.
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Arithmetic Shift Left One Bit: ASL
+ * C <- 7 6 5 4 3 2 1 0 <- 0
+ * Flags: N, Z, C
+ * */
int func_ASL(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ if (current_inst->addr_mode == ADDR_MODE_ACC) {
+ unsigned char op_data = cpu_reg.acc;
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = ((op_data & 0x80) != 0);
+ cpu_reg.acc = (op_data << 1);
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+ goto acc_done;
+ }
+ else {
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = ((op_data & 0x80) != 0);
+ op_data = (op_data << 1);
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+acc_done:
+ exec_done = TRUE;
+ return TRUE;
}
static int branch(unsigned char condition) {
unsigned short addr = cpu_reg.pc;
unsigned short br_addr = cpu_reg.pc + rel;
- if (addr >> 8 == br_addr >> 8) {
+ if ((addr >> 8) == (br_addr >> 8)) {
//in page branch.
cpu_reg.pc = br_addr;
exec_done = TRUE;
return branch(cpu_reg.status.zero == 1);
}
-int func_BIT(void) {
- return FALSE;
+/*
+ * Test Bits in Memory with Accumulator: BIT
+ * A & M
+ * Flags: N = M7, V = M6, Z
+ * */
+int func_BIT(void) {
+ int done = FALSE;
+ int ret;
+ unsigned char cmp;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ cmp = get_cpu_data_buf();
+ //cmp N/V/Z flags set.
+ /*
+ * The BIT instruction really performs two distinct operations.
+ * First, it directly transfers the highest and next to highest
+ * bits of the memory operand (that is, seven and six if m
+ * = 1, or fifteen and fourteen if m = 0) to the n and v flags.
+ * It does this without modifying the value in the
+ * accumulator, making it useful for testing the sign of a value
+ * in memory without loading it into one of the
+ * registers. An exception to this is the case where the immediate
+ * addressing mode is used with the BIT
+ * instruction: since it serves no purpose to test the bits of a
+ * constant value, the n and v flags are left unchanged in
+ * this one case.
+ * BITs second operation is to logically AND the value of the
+ * memory operand with the value in the
+ * accumulator, conditioning the z flag in the status register to
+ * reflect whether or not the result of the ANDing was
+ * zero or not, but without storing the result in the accumulator
+ * */
+ //6502 core supports zp and abs only
+ set_negative(cmp);
+ set_BIT_overflow(cmp);
+ set_zero(cpu_reg.acc & cmp);
+
+ exec_done = TRUE;
+ return TRUE;
}
/*
return branch(cpu_reg.status.overflow == 1);
}
+/*
+ * Clear Carry Flag: CLC
+ * 0 -> C
+ * Flags: C = 0
+ * */
int func_CLC(void) {
- return FALSE;
+ cpu_reg.status.carry = 0;
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Clear Decimal Mode: CLD
+ * 0 -> D
+ * Flags: D = 0
+ *
+ * NOTE: Decimal mode is not implemented on NES core.
+ * */
int func_CLD(void) {
- return FALSE;
+ cpu_reg.status.decimal = 0;
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Clear Interrupt Disable Status: CLI
+ * 0 -> I
+ * Flags: I = 0
+ * */
int func_CLI(void) {
- return FALSE;
+ cpu_reg.status.irq_disable = 0;
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Clear Overflow Flag: CLV
+ * 0 -> V
+ * Flags: V = 0
+ * */
int func_CLV(void) {
- return FALSE;
+ cpu_reg.status.overflow = 0;
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Compare Memory and Accumulator: CMP
+ * A - M
+ * Flags: N, Z, C
+ * */
int func_CMP(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char cmp;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ cmp = get_cpu_data_buf();
+ //cmp C/N/Z flags set.
+ set_CMP_carry(cpu_reg.acc, cmp);
+ set_negative(cpu_reg.acc - cmp);
+ set_zero(cpu_reg.acc - cmp);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Compare Memory and Index X: CPX
+ * X - M
+ * Flags: N, Z, C
+ * */
int func_CPX(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char cmp;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ cmp = get_cpu_data_buf();
+ //cmp C/N/Z flags set.
+ set_CMP_carry(cpu_reg.x, cmp);
+ set_negative(cpu_reg.x - cmp);
+ set_zero(cpu_reg.x - cmp);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Compare Memory with Index Y: CPY
+ * Y - M
+ * Flags: N, Z, C
+ * */
int func_CPY(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char cmp;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ cmp = get_cpu_data_buf();
+ //cmp C/N/Z flags set.
+
+/*
+ * Subtract the data located at the effective address specified
+ * by the operand from the contents of the Y
+ * register, setting the carry, zero, and negative flags based
+ * on the result, but without altering the contents of either
+ * the memory location or the register. The comparison is of
+ * unsigned values only (expect for signed comparison
+ * for equality).
+ * */
+ set_CMP_carry(cpu_reg.y, cmp);
+ set_negative(cpu_reg.y - cmp);
+ set_zero(cpu_reg.y - cmp);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Decrement Memory by One: DEC
+ * M - 1 -> M
+ * Flags: N, Z
+ * */
int func_DEC(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ op_data--;
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+ exec_done = TRUE;
+ return TRUE;
}
/*
return TRUE;
}
+/*
+ * Exclusive-OR Memory with Accumulator: EOR
+ * A ^ M -> A
+ * Flags: N, Z
+ * */
int func_EOR(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char data;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ data = get_cpu_data_buf();
+ cpu_reg.acc = cpu_reg.acc ^ data;
+ //N/Z flags set.
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Increment Memory by One: INC
+ * M + 1 -> M
+ * Flags: N, Z
+ * */
int func_INC(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ op_data++;
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+ exec_done = TRUE;
+ return TRUE;
}
/*
return TRUE;
}
-int func_JMP(void) {
+static int jmp(int cycle, int *done) {
+ switch (current_inst->addr_mode) {
+ case ADDR_MODE_ABS:
+ //takes 2 cycles.
+ if (cycle == 0) {
+ load_addr(cpu_reg.pc, 1);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (cycle == 1) {
+ load_addr(cpu_reg.pc, 2);
+ cpu_reg.pc++;
+ *done = TRUE;
+ return TRUE;
+ }
+ break;
+
+ case ADDR_MODE_IND:
+ //takes 4 cycles.
+ if (cycle == 0) {
+ load_addr(cpu_reg.pc, 1);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (cycle == 1) {
+ load_addr(cpu_reg.pc, 2);
+ cpu_reg.pc++;
+ return TRUE;
+ }
+ else if (cycle == 2) {
+ load_memory(get_cpu_addr_buf());
+ return TRUE;
+ }
+ else if (cycle == 3) {
+ unsigned char low, hi;
+ unsigned short addr;
+ low = get_cpu_data_buf();
+ hi = load_memory(get_cpu_addr_buf() + 1);
+ addr = (hi << 8) | low;
+ set_cpu_addr_buf(addr);
+ *done = TRUE;
+ return TRUE;
+ }
+ break;
+
+ default:
+ return FALSE;
+ }
return FALSE;
}
+/*
+ * Jump to New Location: JMP
+ * Jump to new location
+ * Flags: none
+ * */
+int func_JMP(void) {
+ int done = FALSE;
+ int ret;
+
+ ret = jmp(current_exec_index, &done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ cpu_reg.pc = get_cpu_addr_buf();
+
+ exec_done = TRUE;
+ return TRUE;
+}
+
+/*
+ * Jump to New Location Saving Return Address: JSR
+ * Jump to Subroutine
+ * Flags: none
+ * */
int func_JSR(void) {
+ int done = FALSE;
+
+ //cycle 1
+ if (current_exec_index == 0) {
+ //save return addr(-1) hi.
+ //pc + 1 => jsr abslo abshi - 1
+ push((cpu_reg.pc + 1) >> 8);
+ return TRUE;
+ }
+ //cycle 2
+ else if (current_exec_index == 1) {
+ //save return addr(-1) low.
+ push(cpu_reg.pc + 1);
+ return TRUE;
+ }
+ //cycle 3,4
+ else if (current_exec_index < 4) {
+ return jmp(current_exec_index - 2, &done);
+ }
+ //cycle 5
+ else if (current_exec_index == 4) {
+ cpu_reg.pc = get_cpu_addr_buf();
+ exec_done = TRUE;
+ return TRUE;
+ }
return FALSE;
}
return TRUE;
}
+/*
+ * Logical Shift Right One Bit: LSR
+ * 0 -> 7 6 5 4 3 2 1 0 -> C
+ * Flags: N, Z, C
+ * */
int func_LSR(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ if (current_inst->addr_mode == ADDR_MODE_ACC) {
+ unsigned char op_data = cpu_reg.acc;
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = (op_data & 0x01);
+ cpu_reg.acc = (op_data >> 1);
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+ goto acc_done;
+ }
+ else {
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = (op_data & 0x01);
+ op_data = (op_data >> 1);
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+acc_done:
+ exec_done = TRUE;
+ return TRUE;
}
int func_NOP(void) {
return FALSE;
}
+/*
+ * OR Memory with Accumulator: ORA
+ * A | M -> A
+ * Flags: N, Z
+ * */
int func_ORA(void) {
+ int done = FALSE;
+ int ret;
+ unsigned char data;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ data = get_cpu_data_buf();
+ cpu_reg.acc = cpu_reg.acc | data;
+ //N/Z flags set.
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+
+ exec_done = TRUE;
+ return TRUE;
+}
+
+/*
+ * push takes 2 cycles.
+ * */
+static int push_op(unsigned char data, int *done) {
+ //cycle 1
+ if (current_exec_index == 0) {
+ push(data);
+ return TRUE;
+ }
+ //cycle 2
+ else if (current_exec_index == 1) {
+ //cycle 2 doesn't do enything.
+ *done = TRUE;
+ return TRUE;
+ }
return FALSE;
}
+/*
+ * Push Accumulator on Stack: PHA
+ * A -> S
+ * Flags: none
+ * */
int func_PHA(void) {
- return FALSE;
+ int ret;
+ int done = FALSE;
+ ret = push_op(cpu_reg.acc, &done);
+ exec_done = done;
+ return ret;
}
int func_PHP(void) {
return FALSE;
}
-int func_PLA(void) {
+/*
+ * pull takes 3 cycles.
+ * */
+static int pull_op(int *done) {
+ //cycle 1
+ if (current_exec_index == 0) {
+ pop();
+ return TRUE;
+ }
+ //cycle 2
+ else if (current_exec_index == 1) {
+ //cycle 2 doesn't do enything.
+ return TRUE;
+ }
+ //cycle 3
+ else if (current_exec_index == 2) {
+ //cycle 3 caller must xfer data from cpu data buf
+ *done = TRUE;
+ return TRUE;
+ }
return FALSE;
}
+/*
+ * Pull Accumulator from Stack: PLA
+ * S -> A
+ * Flags: N, Z
+ * */
+int func_PLA(void) {
+ int ret;
+ int done = FALSE;
+ ret = pull_op(&done);
+ if (done) {
+ cpu_reg.acc = get_cpu_data_buf();
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+ }
+ exec_done = done;
+ return ret;
+}
+
int func_PLP(void) {
return FALSE;
}
+/*
+ * Rotate Left One Bit: ROL
+ * C <- 7 6 5 4 3 2 1 0 <- C
+ * Flags: N, Z, C
+ * */
int func_ROL(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ if (current_inst->addr_mode == ADDR_MODE_ACC) {
+ unsigned char op_data = cpu_reg.acc;
+ unsigned char old_carry = cpu_reg.status.carry;
+
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = ((op_data & 0x80) != 0);
+ cpu_reg.acc = (op_data << 1);
+ if (old_carry)
+ cpu_reg.acc |= 0x01;
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+ goto acc_done;
+ }
+ else {
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ unsigned char old_carry = cpu_reg.status.carry;
+
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = ((op_data & 0x80) != 0);
+ op_data = (op_data << 1);
+ if (old_carry)
+ op_data |= 0x01;
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+acc_done:
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Rotate Right One Bit: ROR
+ * C -> 7 6 5 4 3 2 1 0 -> C
+ * Flags: N, Z, C
+ * */
int func_ROR(void) {
- return FALSE;
+ int done = FALSE;
+ int operation = FALSE;
+ unsigned char data;
+ int ret;
+
+ if (current_inst->addr_mode == ADDR_MODE_ACC) {
+ unsigned char op_data = cpu_reg.acc;
+ unsigned char old_carry = cpu_reg.status.carry;
+
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = (op_data & 0x01);
+ cpu_reg.acc = (op_data >> 1);
+ if (old_carry)
+ cpu_reg.acc |= 0x80;
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+ goto acc_done;
+ }
+ else {
+ ret = memory_to_memory(&operation, &done);
+ if (!ret)
+ return FALSE;
+
+ if (operation) {
+ unsigned char op_data = get_cpu_data_buf();
+ unsigned char old_carry = cpu_reg.status.carry;
+
+ //set carry flag from the pre-opration value.
+ cpu_reg.status.carry = (op_data & 0x01);
+ op_data = (op_data >> 1);
+ if (old_carry)
+ op_data |= 0x80;
+ set_cpu_data_buf(op_data);
+ return TRUE;
+ }
+ }
+
+ if (!done)
+ return TRUE;
+
+ // N/Z flags set.
+ data = get_cpu_data_buf();
+ set_negative(data);
+ set_zero(data);
+
+acc_done:
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Return from Interrupt: RTI
+ * Return from Interrupt
+ * Flags: all
+ * */
int func_RTI(void) {
+ //cycle 1
+ if (current_exec_index == 0) {
+ //pop statu reg.
+ pop();
+ return TRUE;
+ }
+ //cycle 2
+ else if (current_exec_index == 1) {
+ unsigned char data;
+ //set status reg
+ data = get_cpu_data_buf();
+ memcpy(&cpu_reg.status, &data, sizeof(data));
+ //pop return addr low.
+ pop();
+ return TRUE;
+ }
+ //cycle 3
+ else if (current_exec_index == 2) {
+ //set return addr low.
+ set_cpu_addr_buf(get_cpu_data_buf());
+ //pop return addr hi.
+ pop();
+ return TRUE;
+ }
+ //cycle 4
+ else if (current_exec_index == 3) {
+ unsigned char hi, lo;
+ unsigned short addr;
+
+ //set return addr hi
+ lo = get_cpu_addr_buf();
+ hi = get_cpu_data_buf();
+ addr = (hi << 8) | lo;
+ set_cpu_addr_buf(addr);
+ return TRUE;
+ }
+ //cycle 5
+ else if (current_exec_index == 4) {
+ //set pc = addr
+ cpu_reg.pc = get_cpu_addr_buf();
+ exec_done = TRUE;
+ return TRUE;
+ }
return FALSE;
}
+/*
+ * Return from Subroutine: RTS
+ * Return from Subroutine
+ * Flags: none
+ * */
int func_RTS(void) {
+
+ //cycle 1
+ if (current_exec_index == 0) {
+ //pop return addr low.
+ pop();
+ return TRUE;
+ }
+ //cycle 2
+ else if (current_exec_index == 1) {
+ //set return addr low.
+ set_cpu_addr_buf(get_cpu_data_buf());
+ return TRUE;
+ }
+ //cycle 3
+ else if (current_exec_index == 2) {
+ //pop return addr hi.
+ pop();
+ return TRUE;
+ }
+ //cycle 4
+ else if (current_exec_index == 3) {
+ unsigned char hi, lo;
+ unsigned short addr;
+
+ //set return addr hi
+ lo = get_cpu_addr_buf();
+ hi = get_cpu_data_buf();
+ addr = (hi << 8) | lo;
+ set_cpu_addr_buf(addr);
+ return TRUE;
+ }
+ //cycle 5
+ else if (current_exec_index == 4) {
+ //set pc = addr + 1
+ cpu_reg.pc = get_cpu_addr_buf() + 1;
+ exec_done = TRUE;
+ return TRUE;
+ }
return FALSE;
}
+/*
+ * Subtract Memory from Accumulator with Borrow: SBC
+ * A - M - ~C -> A
+ * Flags: N, V, Z, C
+ * */
int func_SBC(void) {
- return FALSE;
+ int done = FALSE;
+ int ret;
+ unsigned char data;
+ unsigned char c_comp;
+
+ ret = load_addr_mode(&done);
+ if (!ret)
+ return FALSE;
+
+ if (!done)
+ return TRUE;
+
+ data = get_cpu_data_buf();
+ c_comp = (cpu_reg.status.carry == 0 ? 1 : 0);
+
+ //signed, unsigned overflow check.
+ set_SUB_carry(cpu_reg.acc, data, c_comp);
+ set_SUB_overflow(cpu_reg.acc, data, c_comp);
+
+ //subtract data with carry to accumurator.
+ cpu_reg.acc = cpu_reg.acc - data - c_comp;
+
+ // N/Z flags set.
+ set_negative(cpu_reg.acc);
+ set_zero(cpu_reg.acc);
+
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Set Carry Flag: SEC
+ * 1 -> C
+ * Flags: C = 1
+ * */
int func_SEC(void) {
- return FALSE;
+ cpu_reg.status.carry = 1;
+ exec_done = TRUE;
+ return TRUE;
}
+/*
+ * Set Decimal Mode: SED
+ * 1 -> D
+ * Flags: D = 1
+ *
+ * NOTE: decimal mode is not supported on NES core
+ * */
int func_SED(void) {
+ cpu_reg.status.decimal = 1;
+ fprintf(stderr, "decimal mode is not supported!!!\n");
return FALSE;
}
return TRUE;
}
+/* ------------------ 6502 execution.. ------------------- */
+
/*
* decode6502:
* return execution cycle count
return FALSE;
}
- dprint("decode inst: %02x > %s, %d cycle, %d len\n",
+ /*dprint("decode inst: %02x > %s, %d cycle, %d len\n",
inst, omap->mnemonic, omap->cycle, omap->inst_len);
+*/
current_inst = omap;
- current_exec_index = 0;
return TRUE;
}
int test_and_set_exec(void) {
int ret;
ret = exec_done;
- if (exec_done)
+ if (exec_done) {
exec_done = FALSE;
+ current_exec_index = 0;
+ }
return ret;
}
int ret;
ret = current_inst->func();
current_exec_index++;
+
+#ifdef cycle_check
+ if (exec_done && (current_inst->cycle - 1 != current_exec_index)) {
+ if (current_inst->cycle_aux && (
+ current_inst->addr_mode == ADDR_MODE_ABS_X ||
+ current_inst->addr_mode == ADDR_MODE_ABS_Y ||
+ current_inst->addr_mode == ADDR_MODE_INDIR_INDEX ) &&
+ (current_inst->cycle == current_exec_index)) {
+ ;
+ }
+ else if ((current_inst->addr_mode == ADDR_MODE_REL) &&
+ ((current_inst->cycle == current_exec_index) ||
+ (current_inst->cycle + 1 == current_exec_index ))) {
+ ;
+ }
+ else {
+ fprintf(stderr, "instruction cycle check error!!\n");
+ return FALSE;
+ }
+ }
+#endif
+
+ return ret;
+}
+
+int reset_exec6502(void) {
+ switch (current_exec_index++) {
+ case 0:
+ //step 1: load intvec low.
+ load_addr(RESET_VECTOR, 1);
+ return TRUE;
+ case 1:
+ //step 2: load intvec hi.
+ load_addr(RESET_VECTOR + 1, 2);
+ return TRUE;
+ case 2:
+ //step 3: set pc
+ cpu_reg.pc = get_cpu_addr_buf();
+ //set status flag
+ cpu_reg.status.decimal = 0;
+ cpu_reg.status.irq_disable = 1;
+ intr_done = TRUE;
+ return TRUE;
+ }
+ return FALSE;
+}
+
+int reset6502(void) {
+ current_exec_index = 0;
+ return reset_exec6502();
+}
+
+int nmi6502(void) {
+ dprint("nmi...\n");
+
+ //nmi6502 is always called when current instruction execution is done.
+ switch (current_exec_index++) {
+ case 0:
+ //first: push pc hi.
+ push(cpu_reg.pc >> 8);
+ return TRUE;
+ case 1:
+ //second: push pc low.
+ push(cpu_reg.pc);
+ return TRUE;
+ case 2:
+ {
+ //step 3, push status_reg
+ unsigned char stat;
+ memcpy(&stat, &cpu_reg.status, sizeof(stat));
+ push(stat);
+ return TRUE;
+ }
+ case 3:
+ //step 4: load intvec low.
+ load_addr(NMI_VECTOR, 1);
+ return TRUE;
+ case 4:
+ //step 5: load intvec hi.
+ load_addr(NMI_VECTOR + 1, 2);
+ return TRUE;
+ case 5:
+ //step 6: set pc
+ cpu_reg.pc = get_cpu_addr_buf();
+ //set status flag
+ cpu_reg.status.decimal = 0;
+ cpu_reg.status.irq_disable = 1;
+
+ intr_done = TRUE;
+ return TRUE;
+ }
+ return FALSE;
+}
+
+int test_and_set_intr(void) {
+ int ret;
+ ret = intr_done;
+ if (ret) {
+ current_exec_index = 0;
+ intr_done = FALSE;
+ }
return ret;
}
cpu_reg.pc += offset;
}
+int init_6502core(void) {
+ memset(&cpu_reg, 0, sizeof(struct cpu_6502));
+ current_inst = NULL;
+ current_exec_index = 0;
+ exec_done = FALSE;
+ intr_done = FALSE;
+ return TRUE;
+}
+
+/* for debug.c */
+
void dump_6502(int full) {
+ printf("\nclock: %09d\n", get_clock_cnt());
if (full)
printf("6502 CPU registers:\n");
- printf("pc: %04x\n", cpu_reg.pc);
+ printf(" pc: %04x\n", cpu_reg.pc);
if (full) {
- printf("acc: %02x\n", cpu_reg.acc);
- printf("x: %02x\n", cpu_reg.x);
- printf("y: %02x\n", cpu_reg.y);
- printf("sp: %02x\n", cpu_reg.sp);
- printf("status:\n");
- printf(" negative: %d\n", cpu_reg.status.negative);
- printf(" overflow: %d\n", cpu_reg.status.overflow);
- printf(" break: %d\n", cpu_reg.status.break_mode);
- printf(" decimal: %d\n", cpu_reg.status.decimal);
- printf(" irq: %d\n", cpu_reg.status.irq_disable);
- printf(" zero: %d\n", cpu_reg.status.zero);
- printf(" carry: %d\n", cpu_reg.status.carry);
+ printf(" acc: %02x\n", cpu_reg.acc);
+ printf(" x: %02x\n", cpu_reg.x);
+ printf(" y: %02x\n", cpu_reg.y);
+ printf(" sp: %02x\n", cpu_reg.sp);
+ printf(" status:\n");
+ printf(" negative: %d\n", cpu_reg.status.negative);
+ printf(" overflow: %d\n", cpu_reg.status.overflow);
+ printf(" break: %d\n", cpu_reg.status.break_mode);
+ printf(" decimal: %d\n", cpu_reg.status.decimal);
+ printf(" irq: %d\n", cpu_reg.status.irq_disable);
+ printf(" zero: %d\n", cpu_reg.status.zero);
+ printf(" carry: %d\n", cpu_reg.status.carry);
printf("-------------------\n");
}
//printf("data: %02x\n", cpu_data_buffer);
}
-int init_6502core(void) {
- memset(&cpu_reg, 0, sizeof(struct cpu_6502));
- current_inst = NULL;
- current_exec_index = 0;
- exec_done = FALSE;
- return TRUE;
+int disas_inst(unsigned short addr) {
+ unsigned char inst;
+ unsigned char dbg_get_byte(unsigned short addr);
+ void disasm(const char* mnemonic, int addr_mode, unsigned short pc);
+
+ inst = dbg_get_byte(addr);
+ struct opcode_map * omap = &opcode_list[inst];
+
+ disasm(omap->mnemonic, omap->addr_mode, addr);
+ return omap->inst_len;
+}
+
+void report_exec_err(void) {
+ fprintf(stderr, "cpu execute instruction failure @0x%04x.\n", pc_get());
+ fprintf(stderr, "error instruction: %s, cycle:%d\n",
+ current_inst->mnemonic, current_exec_index - 1);
}
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