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Implemented instructions using the Absolute,X addressing mode. There's
light at the end of the tunnel now!
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Seth Morabito
parent
107aca7777
commit
dccf73a6b7
2
README
2
README
@ -55,10 +55,10 @@ ACIAs. More functionality may be considered as time goes on.
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o Indirect [used only by JMP]
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o Zero Page, X-indexed
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o Zero Page, Y-indexed
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o Absolute, X-indexed
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INCOMPLETE ADDRESSING MODES:
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o Relative
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o Absolute, X-indexed
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o Absolute, Y-indexed
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o Indexed Indirect [ (Indirect ,X) ]
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o Indirect Indexed [ (Indirect),Y ]
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@ -207,9 +207,16 @@ public class Cpu implements InstructionTable {
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break;
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case 0x19: // TODO: implement
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break;
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case 0x1d: // TODO: implement
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case 0x1d: // ORA - Logical Inclusive OR - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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a |= j;
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setArithmeticFlags(a);
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break;
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case 0x1e: // TODO: implement
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case 0x1e: // ASL - Arithmetic Shift Left - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = asl(j);
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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case 0x20: // JSR - Jump to Subroutine - $20
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@ -226,7 +233,7 @@ public class Cpu implements InstructionTable {
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setNegativeFlag((k & 0x80) != 0);
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setOverflowFlag((k & 0x40) != 0);
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break;
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case 0x25: // AND - Logical And - Zero Page
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case 0x25: // AND - Logical AND - Zero Page
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j = bus.read(operands[0]);
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a &= j;
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setArithmeticFlags(a);
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@ -240,7 +247,7 @@ public class Cpu implements InstructionTable {
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case 0x28: // PLP - Pull Processor Status - Implied
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setProcessorStatus(stackPop());
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break;
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case 0x29: // AND - Logical And - Immediate
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case 0x29: // AND - Logical AND - Immediate
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a &= operands[0];
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setArithmeticFlags(a);
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break;
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@ -255,12 +262,12 @@ public class Cpu implements InstructionTable {
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setNegativeFlag((k & 0x80) != 0);
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setOverflowFlag((k & 0x40) != 0);
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break;
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case 0x2d: // AND - Logical And - Absolute
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case 0x2d: // AND - Logical AND - Absolute
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j = bus.read(address(operands[0], operands[1]));
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a &= j;
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setArithmeticFlags(a);
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break;
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case 0x2e: // ROL - Rotate Shift Left - Absolute
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case 0x2e: // ROL - Rotate Left - Absolute
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j = bus.read(address(operands[0], operands[1]));
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k = rol(j);
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bus.write(address(operands[0], operands[1]), k);
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@ -271,7 +278,7 @@ public class Cpu implements InstructionTable {
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break;
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case 0x31: // TODO: implement
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break;
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case 0x35: // AND - Logical And - Zero Page,X
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case 0x35: // AND - Logical AND - Zero Page,X
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j = bus.read(zpxAddress(operands[0]));
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a &= j;
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setArithmeticFlags(a);
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@ -287,9 +294,16 @@ public class Cpu implements InstructionTable {
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break;
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case 0x39: // TODO: implement
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break;
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case 0x3d: // TODO: implement
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case 0x3d: // AND - Logical AND - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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a &= j;
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setArithmeticFlags(a);
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break;
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case 0x3e: // TODO: implement
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case 0x3e: // ROL - Rotate Left - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = rol(j);
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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case 0x40: // RTI - Return from Interrupt - Implied
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@ -355,9 +369,15 @@ public class Cpu implements InstructionTable {
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break;
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case 0x59: // TODO: implement
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break;
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case 0x5d: // TODO: implement
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case 0x5d: // EOR - Exclusive OR - Absolute,X
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a ^= bus.read(xAddress(operands[0], operands[1]));
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setArithmeticFlags(a);
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break;
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case 0x5e: // TODO: implement
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case 0x5e: // LSR - Logical Shift Right - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = lsr(j);
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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case 0x60: // RTS - Return from Subroutine - Implied
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@ -454,9 +474,19 @@ public class Cpu implements InstructionTable {
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break;
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case 0x79: // TODO: implement
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break;
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case 0x7d: // TODO: implement
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case 0x7d: // ADC - Add with Carry - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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if (decimalModeFlag) {
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a = adcDecimal(a, j);
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} else {
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a = adc(a, j);
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}
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break;
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case 0x7e: // TODO: implement
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case 0x7e: // ROR - Rotate Right - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = ror(j);
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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case 0x81: // TODO: implement
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@ -519,7 +549,9 @@ public class Cpu implements InstructionTable {
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case 0x9a: // TXS - Transfer X to Stack Pointer - Implied
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setStackPointer(x);
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break;
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case 0x9d: // TODO: implement
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case 0x9d: // STA - Store Accumulator - Absolute,X
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bus.write(xAddress(operands[0], operands[1]), a);
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setArithmeticFlags(a);
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break;
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case 0xa0: // LDY - Load Y Register - Immediate
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@ -556,7 +588,9 @@ public class Cpu implements InstructionTable {
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x = a;
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setArithmeticFlags(x);
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break;
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case 0xac: // TODO: implement
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case 0xac: // LDY - Load Y Register - Absolute
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y = bus.read(address(operands[0], operands[1]));
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setArithmeticFlags(y);
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break;
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case 0xad: // LDA - Load Accumulator - Absolute
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a = bus.read(address(operands[0], operands[1]));
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@ -592,11 +626,13 @@ public class Cpu implements InstructionTable {
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x = getStackPointer();
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setArithmeticFlags(x);
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break;
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case 0xbc: // LDY - Load Y Register - Absolute
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y = bus.read(address(operands[0], operands[1]));
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case 0xbc: // LDY - Load Y Register - Absolute,X
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y = bus.read(xAddress(operands[0], operands[1]));
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setArithmeticFlags(y);
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break;
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case 0xbd: // TODO: implement
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case 0xbd: // LDA - Load Accumulator - Absolute,X
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a = bus.read(xAddress(operands[0], operands[1]));
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setArithmeticFlags(a);
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break;
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case 0xbe: // TODO: implement
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break;
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@ -660,9 +696,14 @@ public class Cpu implements InstructionTable {
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break;
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case 0xd9: // TODO: implement
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break;
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case 0xdd: // TODO: implement
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case 0xdd: // CMP - Compare Accumulator - Absolute,X
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cmp(a, bus.read(xAddress(operands[0], operands[1])));
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break;
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case 0xde: // TODO: implement
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case 0xde: // DEC - Decrement Memory - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = --j & 0xff;
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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case 0xe0: // CPX - Compare X Register - Immediate
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@ -742,9 +783,19 @@ public class Cpu implements InstructionTable {
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break;
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case 0xf9: // TODO: implement
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break;
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case 0xfd: // TODO: implement
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case 0xfd: // SBC - Subtract with Carry - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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if (decimalModeFlag) {
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a = sbcDecimal(a, j);
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} else {
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a = sbc(a, j);
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}
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break;
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case 0xfe: // TODO: implement
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case 0xfe: // INC - Increment Memory Location - Absolute,X
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j = bus.read(xAddress(operands[0], operands[1]));
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k = ++j & 0xff;
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bus.write(xAddress(operands[0], operands[1]), k);
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setArithmeticFlags(k);
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break;
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/* Unimplemented Instructions */
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@ -1461,6 +1512,22 @@ public class Cpu implements InstructionTable {
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return ((hiByte<<8)|lowByte);
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}
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/**
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* Given a hi byte and a low byte, return the Absolute,X
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* offset address.
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*/
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int xAddress(int lowByte, int hiByte) {
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return (address(lowByte, hiByte)+getXRegister()) & 0xffff;
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}
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/**
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* Given a hi byte and a low byte, return the Absolute,Y
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* offset address.
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*/
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int yAddress(int lowByte, int hiByte) {
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return (address(lowByte, hiByte)+getYRegister()) & 0xffff;
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}
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/**
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* Given a single byte, compute the Zero Page,X offset address.
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*/
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1050
src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java
Normal file
1050
src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java
Normal file
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