diff --git a/src/knx/tp_frame.h b/src/knx/tp_frame.h
index a7475c5c..cd900a62 100644
--- a/src/knx/tp_frame.h
+++ b/src/knx/tp_frame.h
@@ -19,13 +19,16 @@
 #define TP_FRAME_FLAG_ECHO 0b00010000
 
 // Means that the frame is processed by this device
-#define TP_FRAME_FLAG_ADDRESSED 0b00000100
+#define TP_FRAME_FLAG_ADDRESSED 0b00001000
 
-// Means that the frame has been acked by this device.
-#define TP_FRAME_FLAG_ACKING 0b00000010
+// Means that the frame has been acked with BUSY
+#define TP_FRAME_FLAG_ACK_BUSY 0b00000100
 
-// Means that the frame has been acked by other (Busmontior)
-#define TP_FRAME_FLAG_ACKED 0b00000001
+// Means that the frame has been acked with NACK
+#define TP_FRAME_FLAG_ACK_NACK 0b00000010
+
+// Means that the frame has been acked
+#define TP_FRAME_FLAG_ACK 0b00000001
 
 class TpFrame
 {
diff --git a/src/knx/tpuart_data_link_layer.cpp b/src/knx/tpuart_data_link_layer.cpp
index 67e9e256..a0114540 100644
--- a/src/knx/tpuart_data_link_layer.cpp
+++ b/src/knx/tpuart_data_link_layer.cpp
@@ -61,6 +61,8 @@
 // acknowledge services (device is transparent in bus monitor mode)
 #define L_ACKN_IND 0x00
 #define L_ACKN_MASK 0x33
+#define L_ACKN_BUSY_MASK 0x0C
+#define L_ACKN_NACK_MASK 0xC0
 #define L_DATA_CON 0x0B
 #define L_DATA_CON_MASK 0x7F
 #define SUCCESS 0x80
@@ -139,11 +141,11 @@ void printFrame(TpFrame *tpframe)
     print((tpframe->flags() & TP_FRAME_FLAG_INVALID) ? 'I' : '_');   // Invalid
     print((tpframe->flags() & TP_FRAME_FLAG_EXTENDED) ? 'E' : '_');  // Extended
     print((tpframe->flags() & TP_FRAME_FLAG_REPEATED) ? 'R' : '_');  // Repeat
-    print((tpframe->flags() & TP_FRAME_FLAG_ECHO) ? 'O' : '_');      // My own
-    print((tpframe->flags() & 0b00001000) ? 'x' : '_');              // Reserve
-    print((tpframe->flags() & TP_FRAME_FLAG_ADDRESSED) ? 'D' : '_'); // For me
-    print((tpframe->flags() & TP_FRAME_FLAG_ACKING) ? 'A' : '_');    // ACK recevied
-    print((tpframe->flags() & TP_FRAME_FLAG_ACKED) ? 'A' : '_');     // ACK sent
+    print((tpframe->flags() & TP_FRAME_FLAG_ECHO) ? 'T' : '_');      // Send by me
+    print((tpframe->flags() & TP_FRAME_FLAG_ADDRESSED) ? 'D' : '_'); // Recv for me
+    print((tpframe->flags() & TP_FRAME_FLAG_ACK_NACK) ? 'N' : '_');  // ACK + NACK
+    print((tpframe->flags() & TP_FRAME_FLAG_ACK_BUSY) ? 'B' : '_');  // ACK + BUSY
+    print((tpframe->flags() & TP_FRAME_FLAG_ACK) ? 'A' : '_');       // ACK
     print("] ");
     printHex("( ", tpframe->data(), tpframe->size(), false);
     print(")");
@@ -295,7 +297,13 @@ void TpUartDataLinkLayer::processRxByte()
              */
             if (_rxFrame->size() > 0)
             {
-                _rxFrame->addFlags(TP_FRAME_FLAG_ACKED);
+                if (!(byte & L_ACKN_BUSY_MASK))
+                    _rxFrame->addFlags(TP_FRAME_FLAG_ACK_BUSY);
+
+                if (!(byte & L_ACKN_NACK_MASK))
+                    _rxFrame->addFlags(TP_FRAME_FLAG_ACK_NACK);
+
+                _rxFrame->addFlags(TP_FRAME_FLAG_ACK);
                 processRxFrameComplete();
             }
             // println("L_ACKN_IND");
@@ -414,7 +422,7 @@ void TpUartDataLinkLayer::processRxFrameByte(uint8_t byte)
                     if (_txState == TX_IDLE)
                     {
                         // Speichere das ein Acking erfolgen soll
-                        _rxFrame->addFlags(TP_FRAME_FLAG_ACKING);
+                        _rxFrame->addFlags(TP_FRAME_FLAG_ACK);
 
                         // und im TPUart damit dieser das ACK schicken kann
                         _platform.writeUart(U_ACK_REQ | U_ACK_REQ_ADRESSED);