483 lines
11 KiB
C
483 lines
11 KiB
C
//
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// Created by william on 1/9/24.
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//
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#include "decoding.h"
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#include <assert.h>
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#include "log.h"
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address decode_operand_addr(AddressingMode addr_mode, bool *page_crossing) {
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CPU *registers = cpu_get_state();
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address operand_addr;
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if (addr_mode == ADDR_MODE_ZERO_PAGE) {
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operand_addr = cpu_get_next_byte();
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} else if (addr_mode == ADDR_MODE_ZERO_PAGE_INDEXED_X) {
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operand_addr = (cpu_get_next_byte() + registers->x) & 0xff;
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} else if (addr_mode == ADDR_MODE_ZERO_PAGE_INDEXED_Y) {
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operand_addr = (cpu_get_next_byte() + registers->y) & 0xff;
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} else if (addr_mode == ADDR_MODE_ABSOLUTE) {
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operand_addr = cpu_get_next_word();
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} else if (addr_mode == ADDR_MODE_ABSOLUTE_INDEXED_X) {
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word addr = cpu_get_next_word();
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word new_addr = addr + registers->x;
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*page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
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operand_addr = new_addr;
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} else if (addr_mode == ADDR_MODE_ABSOLUTE_INDEXED_Y) {
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word addr = cpu_get_next_word();
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word new_addr = addr + registers->y;
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*page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
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operand_addr = new_addr;
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} else if (addr_mode == ADDR_MODE_INDIRECT_JUMP) {
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word addr = cpu_get_next_word();
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if ((addr & 0xff) == 0xff) {
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// Error in NES CPU for JMP op
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word result = mem_get_byte(addr);
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result += mem_get_byte(addr & 0xff00) << 8;
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operand_addr = result;
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} else {
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operand_addr = mem_get_word(addr);
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}
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} else if (addr_mode == ADDR_MODE_INDIRECT_X) {
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byte arg_addr = cpu_get_next_byte();
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word addr = mem_get_byte((arg_addr + registers->x) & 0xff);
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addr += mem_get_byte((arg_addr + registers->x + 1) & 0xff) << 8;
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operand_addr = addr;
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} else if (addr_mode == ADDR_MODE_INDIRECT_Y) {
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byte arg_addr = cpu_get_next_byte();
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word addr = mem_get_byte(arg_addr) + (mem_get_byte((arg_addr + 1) & 0xff) << 8);
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word new_addr = addr + registers->y;
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*page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
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operand_addr = new_addr;
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} else {
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assert(false);
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}
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log_trace("Operand address: %#02x, Addressing mode: %s", operand_addr, get_addr_mode_name(addr_mode));
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return operand_addr;
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}
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Operand decode_operand(AddressingMode addr_mode) {
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Operand operand;
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if (addr_mode == ADDR_MODE_ACCUMULATOR) {
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operand.type = OPERAND_TYPE_ACCUMULATOR;
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operand.value = 0;
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operand.is_page_crossing = false;
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} else if (addr_mode == ADDR_MODE_IMMEDIATE) {
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operand.type = OPERAND_TYPE_IMMEDIATE;
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operand.value = cpu_get_next_byte();
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operand.is_page_crossing = false;
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} else {
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operand.type = OPERAND_TYPE_ADDRESS;
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operand.value = decode_operand_addr(addr_mode, &operand.is_page_crossing);
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}
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log_trace("Operand type: %s, value: %#02x", operand_name(&operand), operand.value);
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return operand;
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}
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byte read_operand(Operand operand) {
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switch (operand.type) {
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case OPERAND_TYPE_ACCUMULATOR:
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return cpu_get_state()->accumulator;
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case OPERAND_TYPE_IMMEDIATE:
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return (byte) operand.value;
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case OPERAND_TYPE_ADDRESS:
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return mem_get_byte(operand.value);
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default:
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assert(false);
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}
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}
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char *get_addr_mode_name(AddressingMode addr_mode) {
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switch (addr_mode) {
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case ADDR_MODE_ABSOLUTE:
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return "a";
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case ADDR_MODE_ABSOLUTE_INDEXED_X:
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return "a,x";
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case ADDR_MODE_ABSOLUTE_INDEXED_Y:
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return "a,y";
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case ADDR_MODE_ACCUMULATOR:
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return "A";
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case ADDR_MODE_IMMEDIATE:
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return "#";
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case ADDR_MODE_IMPLICIT:
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return " ";
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case ADDR_MODE_INDIRECT_X:
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return "(d,x)";
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case ADDR_MODE_INDIRECT_Y:
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return "(d,y)";
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case ADDR_MODE_INDIRECT_JUMP:
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return "(a)";
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case ADDR_MODE_RELATIVE:
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return "label";
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case ADDR_MODE_ZERO_PAGE:
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return "d";
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case ADDR_MODE_ZERO_PAGE_INDEXED_X:
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return "d,x";
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case ADDR_MODE_ZERO_PAGE_INDEXED_Y:
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return "d,y";
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}
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}
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char *operand_name(Operand *operand) {
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switch (operand->type) {
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case OPERAND_TYPE_ACCUMULATOR:
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return "Accumulator";
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case OPERAND_TYPE_IMMEDIATE:
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return "Immediate";
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case OPERAND_TYPE_ADDRESS:
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return "Address";
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}
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}
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char *get_op_code_name(byte op) {
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switch (op) {
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case 0x00:
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return "BRK";
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case 0x08:
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return "PHP";
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case 0x0b:
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case 0x2b:
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return "ANC";
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case 0x10:
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return "BPL";
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case 0x18:
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return "CLC";
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case 0x20:
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return "JSR";
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case 0x24:
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case 0x2c:
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return "BIT";
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case 0x28:
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return "PLP";
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case 0x30:
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return "BMI";
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case 0x38:
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return "SEC";
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case 0x40:
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return "RTI";
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case 0x48:
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return "PHA";
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case 0x4c:
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case 0x6c:
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return "JMP";
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case 0x50:
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return "BVC";
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case 0x58:
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return "CLI";
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case 0x60:
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return "RTS";
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case 0x68:
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return "PLA";
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case 0x70:
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return "BVS";
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case 0x78:
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return "SEI";
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case 0x84:
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case 0x8c:
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case 0x94:
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return "STY";
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case 0x88:
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return "DEY";
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case 0x90:
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return "BCC";
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case 0x98:
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return "TYA";
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case 0x9c:
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return "SHY";
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case 0xa0:
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case 0xa4:
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case 0xac:
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case 0xb4:
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case 0xbc:
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return "LDY";
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case 0xa8:
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return "TAY";
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case 0xb0:
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return "BCS";
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case 0xb8:
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return "CLV";
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case 0xc0:
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case 0xc4:
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case 0xcc:
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return "CPY";
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case 0xc8:
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return "INY";
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case 0xd0:
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return "BNE";
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case 0xd8:
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return "CLD";
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case 0xe0:
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case 0xe4:
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case 0xec:
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return "CPX";
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case 0xe8:
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return "INX";
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case 0xf0:
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return "BEQ";
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case 0xf8:
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return "SED";
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case 0x01:
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case 0x05:
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case 0x09:
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case 0x0d:
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case 0x11:
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case 0x15:
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case 0x19:
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case 0x1d:
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return "ORA";
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case 0x21:
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case 0x25:
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case 0x29:
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case 0x2d:
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case 0x31:
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case 0x35:
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case 0x39:
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case 0x3d:
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return "AND";
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case 0x41:
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case 0x45:
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case 0x49:
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case 0x4d:
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case 0x51:
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case 0x55:
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case 0x59:
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case 0x5d:
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return "EOR";
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case 0x61:
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case 0x65:
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case 0x69:
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case 0x6d:
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case 0x71:
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case 0x75:
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case 0x79:
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case 0x7d:
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return "ADC";
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case 0x81:
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case 0x85:
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case 0x8d:
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case 0x91:
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case 0x95:
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case 0x99:
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case 0x9d:
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return "STA";
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case 0xa1:
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case 0xa5:
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case 0xa9:
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case 0xad:
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case 0xb1:
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case 0xb5:
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case 0xb9:
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case 0xbd:
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return "LDA";
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case 0xc1:
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case 0xc5:
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case 0xc9:
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case 0xcd:
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case 0xd1:
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case 0xd5:
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case 0xd9:
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case 0xdd:
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return "CMP";
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case 0xe1:
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case 0xe5:
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case 0xe9:
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case 0xed:
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case 0xf1:
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case 0xf5:
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case 0xf9:
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case 0xfd:
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return "SBC";
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case 0x03:
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case 0x07:
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case 0x0f:
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case 0x13:
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case 0x17:
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case 0x1b:
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case 0x1f:
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return "SLO";
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case 0x23:
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case 0x27:
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case 0x2f:
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case 0x33:
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case 0x37:
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case 0x3b:
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case 0x3f:
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return "RLA";
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case 0x43:
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case 0x47:
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case 0x4f:
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case 0x53:
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case 0x57:
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case 0x5b:
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case 0x5f:
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return "SRE";
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case 0x4b:
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return "ALR";
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case 0x63:
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case 0x67:
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case 0x6f:
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case 0x73:
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case 0x77:
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case 0x7b:
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case 0x7f:
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return "RRA";
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case 0x6b:
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return "ARR";
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case 0x83:
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case 0x87:
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case 0x8f:
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case 0x97:
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return "SAX";
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case 0x8b:
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return "XAA";
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case 0x93:
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case 0x9f:
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return "AHX";
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case 0x9b:
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return "TAS";
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case 0xa3:
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case 0xa7:
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case 0xab:
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case 0xaf:
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case 0xb3:
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case 0xb7:
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case 0xbb:
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case 0xbf:
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return "LAX";
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case 0xc3:
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case 0xc7:
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case 0xcf:
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case 0xd3:
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case 0xd7:
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case 0xdb:
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case 0xdf:
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return "DCP";
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case 0xcb:
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return "AXS";
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case 0xe3:
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case 0xe7:
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case 0xef:
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case 0xf3:
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case 0xf7:
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case 0xfb:
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case 0xff:
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return "ISC";
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case 0xeb:
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return "SBC";
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case 0x06:
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case 0x0a:
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case 0x0e:
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case 0x16:
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case 0x1e:
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return "ASL";
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case 0x26:
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case 0x2a:
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case 0x2e:
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case 0x36:
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case 0x3e:
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return "ROL";
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case 0x46:
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case 0x4a:
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case 0x4e:
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case 0x56:
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case 0x5e:
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return "LSR";
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case 0x66:
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case 0x6a:
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case 0x6e:
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case 0x76:
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case 0x7e:
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return "ROR";
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case 0x86:
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case 0x8e:
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case 0x96:
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return "STX";
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case 0x8a:
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return "TXA";
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case 0x9a:
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case 0xba:
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return "TSX";
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case 0x9e:
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return "SHX";
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case 0xa2:
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case 0xa6:
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case 0xae:
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case 0xb6:
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case 0xbe:
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return "LDX";
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case 0xaa:
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return "TAX";
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case 0xc6:
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case 0xce:
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case 0xd6:
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case 0xde:
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return "DEC";
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case 0xca:
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return "DEX";
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case 0xe6:
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case 0xee:
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case 0xf6:
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case 0xfe:
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return "INC";
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case 0x02:
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case 0x12:
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case 0x22:
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case 0x32:
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case 0x42:
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case 0x52:
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case 0x62:
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case 0x72:
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case 0x92:
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case 0xb2:
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case 0xd2:
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case 0xf2:
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return "STP";
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case 0x04:
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case 0x0c:
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case 0x14:
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case 0x1c:
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case 0x1a:
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case 0x34:
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case 0x3a:
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case 0x3c:
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case 0x44:
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case 0x54:
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case 0x5a:
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case 0x5c:
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case 0x64:
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case 0x74:
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case 0x7a:
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case 0x7c:
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case 0x80:
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case 0x82:
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case 0x89:
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case 0xc2:
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case 0xd4:
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case 0xda:
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case 0xdc:
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case 0xe2:
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case 0xea:
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case 0xf4:
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case 0xfa:
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case 0xfc:
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return "NOP";
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default:
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assert(false);
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}
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} |