diff --git a/src/gateware/cxp_upconn.py b/src/gateware/cxp_upconn.py
index 3aa09b5..d8dfecd 100644
--- a/src/gateware/cxp_upconn.py
+++ b/src/gateware/cxp_upconn.py
@@ -99,20 +99,33 @@ class CXP_UpConn(Module, AutoCSR):
             )
         )
 
+
+        idle_ack = Signal()
+        
         # CXP 2.1 section 9.2.4 
         # Higher priority packet can be inserted into a lower priority packet during transmission
         # Priority lv 0 can be inserted in char boundary of the packet 
         # Priority lv 1-2 need to be inserted in word boundary of the packet
         self.sync.cxp_upconn += [
-            self.tx_fifos.disp_in.eq(disp),
-            self.encoder.disp_in.eq(disp),
-            self.encoder.d.eq(Array(IDLE_CHARS)[tx_wordcount][0]),
-            self.encoder.k.eq(Array(IDLE_CHARS)[tx_wordcount][1]),
             If(tx_en,
                 o.eq(tx_reg[0]),
                 tx_reg.eq(Cat(tx_reg[1:], 0)),
                 tx_bitcount.eq(tx_bitcount + 1),   
 
+                self.tx_fifos.disp_in.eq(disp),
+                self.encoder.disp_in.eq(disp),
+                If(idle_ack,
+                    # reset after asserted
+                    idle_ack.eq(0),
+                    If(tx_wordcount == 3,
+                        self.encoder.d.eq(Array(IDLE_CHARS)[0][0]),
+                        self.encoder.k.eq(Array(IDLE_CHARS)[0][1]),
+                    ).Else(
+                        self.encoder.d.eq(Array(IDLE_CHARS)[tx_wordcount + 1][0]),
+                        self.encoder.k.eq(Array(IDLE_CHARS)[tx_wordcount + 1][1]),
+                    )
+                ),
+
                 # char boundary
                 If(tx_bitcount == 9,
                     tx_bitcount.eq(0),
@@ -129,16 +142,19 @@ class CXP_UpConn(Module, AutoCSR):
                             tx_wordcount.eq(0),
                         ),
 
-                        # word boundary
-                        If(tx_wordcount == 0,
+                        # new word boundary
+                        If(tx_wordcount == 3,
                             If(~self.tx_fifos.pe.n,
                                 idling.eq(0),
                                 priority.eq(self.tx_fifos.pe.o),
+
                                 self.tx_fifos.source_ack[self.tx_fifos.pe.o].eq(1),
                                 tx_reg.eq(self.tx_fifos.source_data[self.tx_fifos.pe.o]),
                                 disp.eq(self.tx_fifos.disp_out[self.tx_fifos.pe.o]),
                             ).Else(
                                 idling.eq(1),
+
+                                idle_ack.eq(1),
                                 tx_reg.eq(self.encoder.output),    
                                 disp.eq(self.encoder.disp_out),
                             )
@@ -148,6 +164,7 @@ class CXP_UpConn(Module, AutoCSR):
                                 tx_reg.eq(self.tx_fifos.source_data[priority]),
                                 disp.eq(self.tx_fifos.disp_out[priority]),
                             ).Else(
+                                idle_ack.eq(1),
                                 tx_reg.eq(self.encoder.output),    
                                 disp.eq(self.encoder.disp_out),
                             )
@@ -174,7 +191,7 @@ class CXP_UpConn(Module, AutoCSR):
         p2 = Signal()
         self.comb += [
            ninth_bit.eq(tx_bitcount == 9),
-           word_bound.eq(tx_wordcount == 0),
+           word_bound.eq(tx_wordcount == 3),
            p1.eq(priority == 1),
            p2.eq(priority == 2),
         ]