diff --git a/MC6809/test/Board.cpp b/MC6809/test/Board.cpp
index 686df01..5b11644 100644
--- a/MC6809/test/Board.cpp
+++ b/MC6809/test/Board.cpp
@@ -28,7 +28,7 @@ void Board::initialise() {
 	updateAciaPins(EightBit::Chip::PinLevel::Low);
 	ACIA().lower(ACIA().CTS());
 	ACIA().powerOn();
-	ACIA().access();
+	accessAcia();
 
 	// Once the reset has completed, we can wire the ACIA event handlers...
 	ACIA().Transmitting.connect(std::bind(&Board::Acia_Transmitting, this, std::placeholders::_1));
@@ -75,13 +75,13 @@ void Board::Bus_WrittenByte_Acia(EightBit::EventArgs&) {
 	updateAciaPins(EightBit::Chip::Low);
 	if (ACIA().selected()) {
 		ACIA().DATA() = peek(ADDRESS());
-		ACIA().access();
+		accessAcia();
 	}
 }
 
 void Board::Bus_ReadingByte_Acia(EightBit::EventArgs&) {
 	updateAciaPins(EightBit::Chip::High);
-	if (ACIA().access())
+	if (accessAcia())
 		poke(ADDRESS(), ACIA().DATA());
 }
 
@@ -115,4 +115,11 @@ void Board::Cpu_ExecutedInstruction_Acia(EightBit::mc6809&) {
 void Board::Acia_Transmitting(EightBit::EventArgs&) {
 	std::cout << ACIA().TDR();
 	ACIA().markTransmitComplete();
-}
\ No newline at end of file
+}
+
+bool Board::accessAcia() {
+	ACIA().raise(ACIA().E());
+	const bool accessed = ACIA().tick();
+	ACIA().lower(ACIA().E());
+	return accessed;
+}
diff --git a/MC6809/test/Board.h b/MC6809/test/Board.h
index 34def79..bece7aa 100644
--- a/MC6809/test/Board.h
+++ b/MC6809/test/Board.h
@@ -14,8 +14,8 @@ class Board : public EightBit::Bus {
 public:
 	Board(const Configuration& configuration);
 
-	EightBit::mc6809& CPU() { return m_cpu; }
-	EightBit::mc6850& ACIA() { return m_acia; }
+	auto& CPU() { return m_cpu; }
+	auto& ACIA() { return m_acia; }
 
 	void initialise();
 
@@ -35,7 +35,7 @@ private:
 	EightBit::Disassembly m_disassembler;
 
 	uint64_t m_totalCycleCount = 0UL;
-	int64_t m_frameCycleCount = 0UL;
+	int64_t m_frameCycleCount = 0L;
 
 	// The m_disassembleAt and m_ignoreDisassembly are used to skip pin events
 	EightBit::register16_t m_disassembleAt = 0x0000;
@@ -64,4 +64,6 @@ private:
 
 	// Use the bus data to update the ACIA access/address pins
 	void updateAciaPins(EightBit::Chip::PinLevel rw);
+
+	bool accessAcia();
 };
diff --git a/MC6850/inc/MC6850.h b/MC6850/inc/MC6850.h
index 51c5796..b899293 100644
--- a/MC6850/inc/MC6850.h
+++ b/MC6850/inc/MC6850.h
@@ -190,59 +190,59 @@ namespace EightBit {
 		};
 
 		// Receive data, (I) Active high
-		PinLevel& RXDATA() { return m_RXDATA; }
+		auto& RXDATA() { return m_RXDATA; }
 
 		// Transmit data, (O) Active high
-		PinLevel& TXDATA() { return m_TXDATA; }
+		auto& TXDATA() { return m_TXDATA; }
 
 		// Request to send, (O) Active low
-		PinLevel& RTS() { return m_RTS; }
+		auto& RTS() { return m_RTS; }
 
 		// Clear to send, (I) Active low
-		PinLevel& CTS() { return m_CTS; }
+		auto& CTS() { return m_CTS; }
 
 		// Data carrier detect, (I) Active low
-		PinLevel& DCD() { return m_DCD; }
+		auto& DCD() { return m_DCD; }
 
 		// Transmit clock, (I) Active high
-		PinLevel& RXCLK() { return m_RXCLK; }
+		auto& RXCLK() { return m_RXCLK; }
 
 		// Receive clock, (I) Active high
-		PinLevel& TXCLK() { return m_TXCLK; }
+		auto& TXCLK() { return m_TXCLK; }
 
 		// Chip select, bit 0, (I) Active high
-		PinLevel& CS0() { return m_CS0; }
+		auto& CS0() { return m_CS0; }
 
 		// Chip select, bit 1, (I) Active high
-		PinLevel& CS1() { return m_CS1; }
+		auto& CS1() { return m_CS1; }
 
 		// Chip select, bit 2, (I) Active low
-		PinLevel& CS2() { return m_CS2; }
+		auto& CS2() { return m_CS2; }
 
 		// Register select, (I) Active high
-		PinLevel& RS() { return m_RS; }
+		auto& RS() { return m_RS; }
 
 		// Read/Write, (I) Read high, write low
-		PinLevel& RW() { return m_RW; }
+		auto& RW() { return m_RW; }
 
 		// ACIA Enable, (I) Active high
-		PinLevel& E() { return m_E; }
+		auto& E() { return m_E; }
 
 		// Interrupt request, (O) Active low
-		PinLevel& IRQ() { return m_IRQ; }
+		auto& IRQ() { return m_IRQ; }
 
 		// Data, (I/O)
-		uint8_t& DATA() { return m_data; }
+		auto& DATA() { return m_data; }
 
 		// Expose these internal registers, so we can update internal state
 
 		// Transmit data register;
-		uint8_t& TDR() { return m_TDR; }
+		auto& TDR() { return m_TDR; }
 
 		// Receive data register;
-		uint8_t& RDR() { return m_RDR; }
+		auto& RDR() { return m_RDR; }
 
-		bool access();
+		bool tick();
 
 		bool selected();
 
@@ -272,12 +272,19 @@ namespace EightBit {
 		bool isTransmitInterruptRequired() const;
 		bool isReceiveInterruptRequired() const;
 
+		bool transmitInterruptEnabled() const { return m_transmitControl == ReadyLowInterruptEnabled;  }
+		bool receiveInterruptEnabled() const { return m_receiveControl == ReceiveInterruptEnable;  }
+
+		bool transmitReadyHigh() const { return m_transmitControl == ReadyHighInterruptDisabled; }
+		bool transmitReadyLow() const { return !transmitReadyHigh(); }
+
 		PinLevel m_RXDATA;
 		PinLevel m_TXDATA;
 
 		PinLevel m_RTS;
 		PinLevel m_CTS;
 		PinLevel m_DCD;
+		PinLevel m_oldDCD;	// So we can detect low -> high transition
 
 		PinLevel m_RXCLK;
 		PinLevel m_TXCLK;
@@ -294,6 +301,8 @@ namespace EightBit {
 
 		uint8_t m_data;
 
+		bool m_statusRead = false;
+
 		// Control registers
 		CounterDivideSelect m_counterDivide;
 		WordSelect m_wordSelect;
diff --git a/MC6850/src/MC6850.cpp b/MC6850/src/MC6850.cpp
index bf7695a..b9b7c6c 100644
Binary files a/MC6850/src/MC6850.cpp and b/MC6850/src/MC6850.cpp differ