diff --git a/MC6809/inc/mc6809.h b/MC6809/inc/mc6809.h
index da98da1..4d13213 100644
--- a/MC6809/inc/mc6809.h
+++ b/MC6809/inc/mc6809.h
@@ -176,6 +176,10 @@ namespace EightBit {
 
 		//
 
+		uint8_t AM_immediate() {
+			return fetchByte();
+		}
+
 		uint8_t AM_direct() {
 			Address_direct();
 			return BUS().read();
@@ -187,13 +191,15 @@ namespace EightBit {
 		}
 
 		uint8_t AM_extended() {
-			AM_extended();
+			Address_extended();
 			return BUS().read();
 		}
 
 		//
 
 		void abx();
+		uint8_t adc(uint8_t operand, uint8_t data);
+		uint8_t add(uint8_t operand, uint8_t data, int carry = 0);
 		uint8_t neg(uint8_t operand);
 
 		register16_t m_d;
diff --git a/MC6809/src/mc6809.cpp b/MC6809/src/mc6809.cpp
index 8eac25a..5531f1b 100644
--- a/MC6809/src/mc6809.cpp
+++ b/MC6809/src/mc6809.cpp
@@ -33,6 +33,16 @@ int EightBit::mc6809::execute(uint8_t cell) {
 	// ABX
 	case 0x3a:	addCycles(3);	abx();								break;		// ABX (inherent)
 
+	// ADC
+	case 0x89:	addCycles(2);	A() = adc(A(), AM_immediate());		break;		// ADC (ADCA, immediate)
+	case 0x99:	addCycles(4);	A() = adc(A(), AM_direct());		break;		// ADC (ADCA, direct)
+	case 0xA9:	addCycles(4);	A() = adc(A(), AM_indexed());		break;		// ADC (ADCA, indexed)
+	case 0xB9:	addCycles(4);	A() = adc(A(), AM_extended());		break;		// ADC (ADCA, extended)
+	case 0xC9:	addCycles(2);	B() = adc(B(), AM_immediate());		break;		// ADC (ADCB, immediate)
+	case 0xD9:	addCycles(4);	B() = adc(B(), AM_direct());		break;		// ADC (ADCB, direct)
+	case 0xE9:	addCycles(4);	B() = adc(B(), AM_indexed());		break;		// ADC (ADCB, indexed)
+	case 0xF9:	addCycles(4);	B() = adc(B(), AM_extended());		break;		// ADC (ADCB, extended)
+
 	// NEG
 	case 0x00:	addCycles(6);	BUS().write(neg(AM_direct()));		break;		// NEG (direct)
 	case 0x40:	addCycles(2);	A() = neg(A());						break;		// NEG (NEGA, inherent)
@@ -62,4 +72,16 @@ uint8_t EightBit::mc6809::neg(uint8_t operand) {
 	setFlag(CC(), ZF, operand == 0);
 	setFlag(CC(), CF, result.word & Bit8);
 	return operand;
+}
+
+uint8_t EightBit::mc6809::adc(uint8_t operand, uint8_t data) {
+	return add(operand, data, CC() & CF);
+}
+
+uint8_t EightBit::mc6809::add(uint8_t operand, uint8_t data, int carry) {
+	const register16_t result = operand + data + carry;
+	setFlag(CC(), NF, result.low & Bit7);
+	setFlag(CC(), ZF, result.low == 0);
+	setFlag(CC(), CF, result.word & Bit8);
+	return result.low;
 }
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