RuiFPB/ksymon
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Started on Zero Page opcodes and tests.

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Seth J. Morabito committed 2008-12-27 13:01:07 -08:00
1 parent de0742f59f
commit ecde55c6b8
6 files changed
+346 -126
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src/main/java/com/loomcom/symon/Cpu.java
+91 -28
View File
@@ -18,7 +18,7 @@ public class Cpu implements InstructionTable {
// Bit 5 is always '1'
public static final int P_OVERFLOW = 0x40;
public static final int P_NEGATIVE = 0x80;
// NMI vector
public static final int IRQ_VECTOR_L = 0xfffa;
public static final int IRQ_VECTOR_H = 0xfffb;
@@ -28,7 +28,7 @@ public class Cpu implements InstructionTable {
// IRQ vector
public static final int NMI_VECTOR_L = 0xfffe;
public static final int NMI_VECTOR_H = 0xffff;
/* The Bus */
private Bus bus;
@@ -42,6 +42,11 @@ public class Cpu implements InstructionTable {
private int sp; // Stack Pointer register, offset into page 1
private int ir; // Instruction register
/* Internal scratch space */
private int lo = 0, hi = 0; // Used in address calculation
private int j = 0, k = 0; // Used for temporary storage
/* Operands for the current instruction */
private int[] operands = new int[2];
private int addr; // The address the most recent instruction
@@ -83,7 +88,7 @@ public class Cpu implements InstructionTable {
sp = 0xff;
// Set the PC to the address stored in the reset vector
pc = CpuUtils.address(bus.read(RST_VECTOR_L), bus.read(RST_VECTOR_H));
pc = address(bus.read(RST_VECTOR_L), bus.read(RST_VECTOR_H));
// Clear instruction register.
ir = 0;
@@ -106,8 +111,6 @@ public class Cpu implements InstructionTable {
* Performs an individual machine cycle.
*/
public void step() {
int lo, hi; // Used in address calculation
// Store the address from which the IR was read, for debugging
addr = pc;
@@ -139,7 +142,7 @@ public class Cpu implements InstructionTable {
// Set the Interrupt Disabled flag. RTI will clear it.
setIrqDisableFlag();
// Load interrupt vector address into PC
pc = CpuUtils.address(bus.read(IRQ_VECTOR_L), bus.read(IRQ_VECTOR_H));
pc = address(bus.read(IRQ_VECTOR_L), bus.read(IRQ_VECTOR_H));
}
break;
case 0x01: // n/a
@@ -150,9 +153,13 @@ public class Cpu implements InstructionTable {
break;
case 0x04: // n/a
break;
case 0x05: // n/a
case 0x05: // ORA - Logical Inclusive OR - Zero Page
a |= bus.read(operands[0]);
setArithmeticFlags(a);
break;
case 0x06: // n/a
case 0x06: // ASL - Arithmetic Shift Left - Zero Page
bus.write(operands[0], asl(bus.read(operands[0])));
setArithmeticFlags(bus.read(operands[0]));
break;
case 0x07: // n/a
break;
@@ -218,7 +225,12 @@ public class Cpu implements InstructionTable {
break;
case 0x23: // n/a
break;
case 0x24: // n/a
case 0x24: // BIT - Bit Test - Zero Page
j = bus.read(operands[0]);
k = a & j;
setZeroFlag(k == 0);
setNegativeFlag((k & 0x80) != 0);
setOverflowFlag((k & 0x40) != 0);
break;
case 0x25: // n/a
break;
@@ -284,7 +296,7 @@ public class Cpu implements InstructionTable {
setProcessorStatus(stackPop());
lo = stackPop();
hi = stackPop();
setProgramCounter(CpuUtils.address(lo, hi));
setProgramCounter(address(lo, hi));
break;
case 0x41: // n/a
break;
@@ -312,7 +324,7 @@ public class Cpu implements InstructionTable {
case 0x4b: // n/a
break;
case 0x4c: // JMP - Jump - Absolute
pc = CpuUtils.address(operands[0], operands[1]);
pc = address(operands[0], operands[1]);
break;
case 0x4d: // n/a
break;
@@ -358,7 +370,7 @@ public class Cpu implements InstructionTable {
case 0x60: // RTS - Return from Subroutine - Implied
lo = stackPop();
hi = stackPop();
setProgramCounter((CpuUtils.address(lo, hi) + 1) & 0xffff);
setProgramCounter((address(lo, hi) + 1) & 0xffff);
break;
case 0x61: // n/a
break;
@@ -753,17 +765,17 @@ public class Cpu implements InstructionTable {
setArithmeticFlags(result);
return result;
}
/**
* Add with Carry (BCD).
*/
public int adcDecimal(int acc, int operand) {
int l, h, result;
l = (acc & 0x0f) + (operand & 0x0f) + getCarryBit();
if ((l & 0xff) > 9) l += 6;
h = (acc >> 4) + (operand >> 4) + (l > 15 ? 1 : 0);
if ((h & 0xff) > 9) h += 6;
if ((h & 0xff) > 9) h += 6;
result = (l & 0x0f) | (h << 4);
result &= 0xff;
setCarryFlag(h > 15);
@@ -771,13 +783,13 @@ public class Cpu implements InstructionTable {
setNegativeFlag(false); // BCD is never negative
setOverflowFlag(false); // BCD never sets overflow flag
return result;
}
}
/**
* Common code for Subtract with Carry. Just calls ADC of the
* one's complement of the operand. This lets the N, V, C, and Z
* flags work out nicely without any additional logic.
*
*
* @param acc
* @param operand
* @return
@@ -788,10 +800,10 @@ public class Cpu implements InstructionTable {
setArithmeticFlags(result);
return result;
}
/**
* Subtract with Carry, BCD mode.
*
*
* @param acc
* @param operand
* @return
@@ -813,7 +825,7 @@ public class Cpu implements InstructionTable {
/**
* Compare two values, and set carry, zero, and negative flags
* appropriately.
*
*
* @param reg
* @param operand
*/
@@ -833,7 +845,28 @@ public class Cpu implements InstructionTable {
zeroFlag = (reg == 0);
negativeFlag = (reg & 0x80) != 0;
}
/**
* Shifts the given value left by one bit, and sets the carry
* flag to the high bit of the initial value.
*
* @param m The value to shift left.
* @return the left shifted value (m * 2).
*/
private int asl(int m) {
setCarryFlag((m & 0x80) != 0);
return (m << 1) & 0xff;
}
/**
* Shifts the given value right by one bit, filling with zeros,
* and sets the carry flag to the low bit of the initial value.
*/
private int lsr(int m) {
setCarryFlag((m & 0x01) != 0);
return (m >>> 1) & 0xff;
}
/**
* @return the negative flag
*/
@@ -876,7 +909,7 @@ public class Cpu implements InstructionTable {
public boolean getCarryFlag() {
return carryFlag;
}
/**
* @return 1 if the carry flag is set, 0 if it is clear.
*/
@@ -946,7 +979,7 @@ public class Cpu implements InstructionTable {
public boolean getIrqDisableFlag() {
return irqDisableFlag;
}
/**
* @return 1 if the interrupt disable flag is set, 0 if it is clear.
*/
@@ -1011,7 +1044,7 @@ public class Cpu implements InstructionTable {
public boolean getBreakFlag() {
return breakFlag;
}
/**
* @return 1 if the break flag is set, 0 if it is clear.
*/
@@ -1046,7 +1079,7 @@ public class Cpu implements InstructionTable {
public boolean getOverflowFlag() {
return overflowFlag;
}
/**
* @return 1 if the overflow flag is set, 0 if it is clear.
*/
@@ -1191,7 +1224,7 @@ public class Cpu implements InstructionTable {
* Returns a string representing the CPU state.
*/
public String toString() {
String opcode = CpuUtils.opcode(ir, operands[0], operands[1]);
String opcode = opcode(ir, operands[0], operands[1]);
StringBuffer sb = new StringBuffer(String.format("$%04X", addr) +
" ");
sb.append(String.format("%-14s", opcode));
@@ -1241,7 +1274,7 @@ public class Cpu implements InstructionTable {
/*
* Increment the PC, rolling over if necessary.
*/
protected void incrementPC() {
void incrementPC() {
if (pc == 0xffff) {
pc = 0;
} else {
@@ -1249,4 +1282,34 @@ public class Cpu implements InstructionTable {
}
}
/**
* Given two bytes, return an address.
*/
int address(int lowByte, int hiByte) {
return ((hiByte<<8)|lowByte);
}
/**
* Given an opcode and its operands, return a formatted name.
*
* @param opcode
* @param operands
* @return
*/
String opcode(int opcode, int op1, int op2) {
String opcodeName = Cpu.opcodeNames[opcode];
if (opcodeName == null) { return "???"; }
StringBuffer sb = new StringBuffer(opcodeName);
switch (Cpu.instructionModes[opcode]) {
case ABS:
sb.append(String.format(" $%04X", address(op1, op2)));
break;
case IMM:
sb.append(String.format(" #$%02X", op1));
}
return sb.toString();
}
}