diff --git a/hardware.hpp b/hardware.hpp
index 415b870..b8f553d 100644
--- a/hardware.hpp
+++ b/hardware.hpp
@@ -45,7 +45,7 @@ class Hardware {
 		*Registers::CTRL_STAT_REG_C = controlRegC;
 	}
 
-	static void txByteBlocking(typename cfg::data_t byte) FORCE_INLINE
+	static void txByteBlocking(const typename cfg::data_t &byte) FORCE_INLINE
 	{
 		while (!(*Registers::CTRL_STAT_REG_A & (1 << CtrlFlagsA::DATA_REG_EMPTY)))
 			;
@@ -53,6 +53,21 @@ class Hardware {
 		*Registers::IO_REG = byte;
 	}
 
+	static void txByteInterrupt(volatile const typename cfg::data_t &byte) FORCE_INLINE
+	{
+		*Registers::IO_REG = byte;
+	}
+
+	static void enableDataRegEmptyInt() FORCE_INLINE
+	{
+		*Registers::CTRL_STAT_REG_B |= (1 << CtrlFlagsB::DATA_REG_EMPTY_INT_ENABLE);
+	}
+
+	static void disableDataRegEmptyInt() FORCE_INLINE
+	{
+		*Registers::CTRL_STAT_REG_B &= ~(1 << CtrlFlagsB::DATA_REG_EMPTY_INT_ENABLE);
+	}
+
   private:
 	struct DataBitsVal {
 		uint8_t regCVal = 0;
diff --git a/hardware0.hpp b/hardware0.hpp
index 848bbdc..521aac6 100644
--- a/hardware0.hpp
+++ b/hardware0.hpp
@@ -127,9 +127,16 @@ class Hardware0<mode, cfg, Driven::INTERRUPT> {
 		HardwareImpl::init();
 	}
 
-	static void txByte(data_t byte) FORCE_INLINE
+	static void txByte(const data_t &byte) FORCE_INLINE
 	{
-		HardwareImpl::txByteBlocking(byte);
+		uint8_t tmpHead = (sm_txHead + 1) % TX_BUFFER_SIZE;
+		while (tmpHead == sm_txTail)
+			;
+
+		sm_txBuffer[tmpHead] = byte;
+		sm_txHead = tmpHead;
+
+		HardwareImpl::enableDataRegEmptyInt();
 	}
 
 	static data_t rxByte() FORCE_INLINE {}
@@ -140,14 +147,25 @@ class Hardware0<mode, cfg, Driven::INTERRUPT> {
 	using HardwareImpl = detail::Hardware<detail::Registers0, detail::ControlFlagsA0, detail::ControlFlagsB0,
 	                                      detail::ControlFlagsC0, cfg, mode, Driven::INTERRUPT>;
 
+	static constexpr auto TX_BUFFER_SIZE = 16;
+
+	static volatile uint8_t sm_txHead;
+	static volatile uint8_t sm_txTail;
+	static volatile data_t sm_txBuffer[TX_BUFFER_SIZE];
+
 	static void rxIntHandler()
 	{
 		// TODO
 	}
 
-	static void dataRegEmptyIntHandler()
+	static void dataRegEmptyIntHandler() FORCE_INLINE
 	{
-		// TODO
+		if (sm_txHead != sm_txTail) {
+			uint8_t tmpTail = (sm_txTail + 1) % TX_BUFFER_SIZE;
+			sm_txTail = tmpTail;
+			HardwareImpl::txByteInterrupt(sm_txBuffer[tmpTail]);
+		} else
+			HardwareImpl::disableDataRegEmptyInt();
 	}
 
 	static void txIntHandler()
@@ -156,6 +174,14 @@ class Hardware0<mode, cfg, Driven::INTERRUPT> {
 	}
 };
 
+template <Mode mode, class cfg>
+volatile uint8_t Hardware0<mode, cfg, Driven::INTERRUPT>::sm_txHead = 0;
+template <Mode mode, class cfg>
+volatile uint8_t Hardware0<mode, cfg, Driven::INTERRUPT>::sm_txTail = 0;
+template <Mode mode, class cfg>
+volatile typename Hardware0<mode, cfg, Driven::INTERRUPT>::data_t
+    Hardware0<mode, cfg, Driven::INTERRUPT>::sm_txBuffer[TX_BUFFER_SIZE];
+
 } // namespace uart
 
 #undef FORCE_INLINE
diff --git a/hardware1.hpp b/hardware1.hpp
index 78b28ca..b053fdc 100644
--- a/hardware1.hpp
+++ b/hardware1.hpp
@@ -102,7 +102,7 @@ class Hardware1 {
 		HardwareImpl::init();
 	}
 
-	static void txByte(data_t byte) FORCE_INLINE
+	static void txByte(const data_t &byte) FORCE_INLINE
 	{
 		HardwareImpl::txByteBlocking(byte);
 	}
@@ -131,9 +131,16 @@ class Hardware1<mode, cfg, Driven::INTERRUPT> {
 		HardwareImpl::init();
 	}
 
-	static void txByte(data_t byte) FORCE_INLINE
+	static void txByte(const data_t &byte) FORCE_INLINE
 	{
-		HardwareImpl::txByteBlocking(byte);
+		uint8_t tmpHead = (sm_txHead + 1) % TX_BUFFER_SIZE;
+		while (tmpHead == sm_txTail)
+			;
+
+		sm_txBuffer[tmpHead] = byte;
+		sm_txHead = tmpHead;
+
+		HardwareImpl::enableDataRegEmptyInt();
 	}
 
 	static data_t rxByte() FORCE_INLINE {}
@@ -144,14 +151,25 @@ class Hardware1<mode, cfg, Driven::INTERRUPT> {
 	using HardwareImpl = detail::Hardware<detail::Registers1, detail::ControlFlagsA1, detail::ControlFlagsB1,
 	                                      detail::ControlFlagsC1, cfg, mode, Driven::INTERRUPT>;
 
+	static constexpr auto TX_BUFFER_SIZE = 16;
+
+	static volatile uint8_t sm_txHead;
+	static volatile uint8_t sm_txTail;
+	static volatile data_t sm_txBuffer[TX_BUFFER_SIZE];
+
 	static void rxIntHandler()
 	{
 		// TODO
 	}
 
-	static void dataRegEmptyIntHandler()
+	static void dataRegEmptyIntHandler() FORCE_INLINE
 	{
-		// TODO
+		if (sm_txHead != sm_txTail) {
+			uint8_t tmpTail = (sm_txTail + 1) % TX_BUFFER_SIZE;
+			sm_txTail = tmpTail;
+			HardwareImpl::txByteInterrupt(sm_txBuffer[tmpTail]);
+		} else
+			HardwareImpl::disableDataRegEmptyInt();
 	}
 
 	static void txIntHandler()
@@ -160,6 +178,14 @@ class Hardware1<mode, cfg, Driven::INTERRUPT> {
 	}
 };
 
+template <Mode mode, class cfg>
+volatile uint8_t Hardware1<mode, cfg, Driven::INTERRUPT>::sm_txHead = 0;
+template <Mode mode, class cfg>
+volatile uint8_t Hardware1<mode, cfg, Driven::INTERRUPT>::sm_txTail = 0;
+template <Mode mode, class cfg>
+volatile typename Hardware1<mode, cfg, Driven::INTERRUPT>::data_t
+    Hardware1<mode, cfg, Driven::INTERRUPT>::sm_txBuffer[TX_BUFFER_SIZE];
+
 #endif
 
 } // namespace uart