想要确保我不必返回并重做大块代码...我将每个操作码作为实现 Runnable 的枚举中的值。有没有更有效的方法可以做到这一点，或者我是否正在编写能够准确运行测试套件 ROM 的东西？
package com.codeblox.nes.cpu;
public class CPU {
private byte x, y, ac, pcl, pch;
private short pc;
private boolean debugEnabled = false, isGood = true;
private static byte [] mainMem = new byte [0x10000];
public Opcode opcode;
CPU(boolean debugEnabled){
opcode =Opcode.nop;
pc = 0;
this.debugEnabled = debugEnabled;
}
public enum Opcode implements Runnable{
adc(){public void run(){System.out.println("adc");}},
and(){public void run(){System.out.println("and");}},
asl(){public void run(){System.out.println("asl");}},
bcc(){public void run(){System.out.println("bcc");}},
bcs(){public void run(){System.out.println("bcs");}},
beq(){public void run(){System.out.println("beq");}},
bit(){public void run(){System.out.println("bit");}},
bmi(){public void run(){System.out.println("bmi");}},
bne(){public void run(){System.out.println("bne");}},
bpl(){public void run(){System.out.println("bpl");}},
brk(){public void run(){System.out.println("brk");}},
bvc(){public void run(){System.out.println("bvc");}},
bvs(){public void run(){System.out.println("bvs");}},
clc(){public void run(){System.out.println("clc");}},
cld(){public void run(){System.out.println("cld");}},
cli(){public void run(){System.out.println("cli");}},
clv(){public void run(){System.out.println("clv");}},
cmp(){public void run(){System.out.println("cmp");}},
cpx(){public void run(){System.out.println("cpx");}},
cpy(){public void run(){System.out.println("cpy");}},
dec(){public void run(){System.out.println("dec");}},
dex(){public void run(){System.out.println("dex");}},
dey(){public void run(){System.out.println("dey");}},
eor(){public void run(){System.out.println("eor");}},
inc(){public void run(){System.out.println("inc");}},
inx(){public void run(){System.out.println("inx");}},
iny(){public void run(){System.out.println("iny");}},
jmp(){public void run(){System.out.println("jmp");}},
jsr(){public void run(){System.out.println("jsr");}},
lda(){public void run(){System.out.println("lda");}},
ldx(){public void run(){System.out.println("ldx");}},
ldy(){public void run(){System.out.println("ldy");}},
lsr(){public void run(){System.out.println("lsr");}},
nop(){public void run(){System.out.println("nop");}},
ora(){public void run(){System.out.println("ora");}},
pha(){public void run(){System.out.println("pha");}},
php(){public void run(){System.out.println("php");}},
pla(){public void run(){System.out.println("pla");}},
plp(){public void run(){System.out.println("plp");}},
rol(){public void run(){System.out.println("rol");}},
ror(){public void run(){System.out.println("ror");}},
rti(){public void run(){System.out.println("rti");}},
rts(){public void run(){System.out.println("rts");}},
sbc(){public void run(){System.out.println("sbc");}},
sec(){public void run(){System.out.println("sec");}},
sed(){public void run(){System.out.println("sed");}},
sei(){public void run(){System.out.println("sei");}},
sta(){public void run(){System.out.println("sta");}},
stx(){public void run(){System.out.println("stx");}},
sty(){public void run(){System.out.println("sty");}},
tax(){public void run(){System.out.println("tax");}},
tay(){public void run(){System.out.println("tay");}},
tsx(){public void run(){System.out.println("tsx");}},
txa(){public void run(){System.out.println("txa");}},
txs(){public void run(){System.out.println("txs");}},
tya(){public void run(){System.out.println("tya");}},
;
public String mnemonic = "";
public String addressMode;
public byte code;
public byte data;
Opcode(){
this.mnemonic = new String();
}
public void print(){
System.out.printf("Opcode: %02X %s %s\n",
this.code,
this.mnemonic.toUpperCase(),
this.addressMode);
}
public String getMode00(byte opcode){
switch(opcode){
case 0x00: return "Immediate";
case 0x04: return "ZeroPaged";
case 0x0C: return "Absolute";
case 0x14: return "IndexedZeroPagedX";
case 0x1C: return "IndexedAbsoluteX";
default: return "Type 0 undefined";
}
}
public String getMode01(byte opcode){
switch(opcode){
case 0x00: return "InirectIndexedZeroPagedX";
case 0x04: return "ZeroPaged";
case 0x08: return "Immediate";
case 0x0C: return "Absolute";
case 0x10: return "IndrectedZeroPagedY";
case 0x14: return "IndexedZeroPagedX";
case 0x18: return "IndexedAbsoluteY";
case 0x1C: return "IndexedAbsoluteX";
default: return "Type 1 Undefined";
}
}
public String getMode02(byte opcode){
switch(opcode){
case 0x00: return "Immediate";
case 0x04: return "ZeroPaged";
case 0x08: return "Accumulator";
case 0x0C: return "Absolute";
case 0x14: return "IndexedZeroPagedX";
case 0x1C: return "IndexedAbsoluteX";
default: return "Type 2 Undefined";
}
}
public String getMode03(byte opcode){ return "";}
public void decode(){
switch(this.code & 0x03){
case 0x00: this.addressMode = getMode00((byte)(this.code & 0x1C)); break;
case 0x01: this.addressMode = getMode01((byte)(this.code & 0x1C)); break;
case 0x02: this.addressMode = getMode02((byte)(this.code & 0x1C)); break;
case 0x03: this.addressMode = getMode03((byte)(this.code & 0x1C)); break;
default: break;
}
}
}
public void init(){
pc = 0;
}
public void start(){
while(isGood){
opcode.code = readMem(pc++);
CPU.Opcode.valueOf(opcode.mnemonic).run();
}
if(!isGood){
System.err.println("isGood == false");
}
}
public byte readMem(short ptr){
return mainMem[ptr];
}
public byte readMem(short ptr, byte addressMode){
return mainMem[ptr];
}
public void exec(){
opcode.decode();
switch(opcode.code & 0xFF){
case 0x69: case 0x65: case 0x75:
case 0x6D: case 0x7D: case 0x79:
case 0x61: case 0x71: opcode.mnemonic = "adc"; break;
case 0x29: case 0x25: case 0x35:
case 0x2D: case 0x3D: case 0x39:
case 0x21: case 0x31: opcode.mnemonic = "and"; break;
case 0x0A: case 0x06: case 0x16:
case 0x0E: case 0x1E: opcode.mnemonic = "asl"; break;
default: opcode.mnemonic = null;
}
//Opcodes.valueOf(this.mnemonic).run();
}
public void testOpcodes(){
opcode.code = 0;
while((opcode.code & 0xFF) < 0xFF){
//System.out.printf("PC = 0x%04X \n", PC);
exec();
if(opcode.mnemonic != null)
opcode.print();
//Opcode.valueOf(opcode.mnemonic).run();
opcode.code++;
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
CPU cpu = new CPU(true);
cpu.init();
cpu.testOpcodes();
}
}
最佳答案
嗯，我认为这是编写 6502 CPU 模拟器的好方法的开始。但它需要一些工作......
问问自己:Java 中的枚举是什么？它有什么好处？
它基本上是一个具有固定数量实例的类，因此非常适合表示静态数据(和行为)并通过关联的方法对其进行分组，以便轻松可见、可测试、可修改。
在各种方法中，您可以使用 switch 语句来区分每个操作码的不同寻址模式和操作:
switch(opcode) {
case 0x00: return "Immediate";
case 0x04: return "ZeroPaged";
case 0x0C: return "Absolute";
case 0x14: return "IndexedZeroPagedX";
case 0x1C: return "IndexedAbsoluteX";
default: return "Type 0 undefined";
}
如果我们想要指令时间等，我们就必须添加更多 switch 语句。
但这是静态数据。这些情况常量应该是枚举属性。这不是应该在枚举中编码的数据吗？我认为是这样，布伦丹·罗伯特也是如此，他写了JACE, the Java Apple Computer Emulator 。他的代码是经过深思熟虑的 Java 枚举的一个很好的例子。
这是 his 6502 CPU's 的前几行操作码枚举:
public enum OPCODE {
ADC_IMM(0x0069, COMMAND.ADC, MODE.IMMEDIATE, 2),
ADC_ZP(0x0065, COMMAND.ADC, MODE.ZEROPAGE, 3),
ADC_ZP_X(0x0075, COMMAND.ADC, MODE.ZEROPAGE_X, 4),
// ...
}
所有静态数据都很好地组合在一起，易于查看，可以在 case 语句等中使用。
关于java - 这是在JAVA中实现6502 CPU模拟器的 "good"方法吗？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40708150/