Index: firmware/App/Services/AlarmMgmt.h
===================================================================
diff -u -r07a5add2dff254f7be3699e4efac2b99d3554847 -r3e525c0567dd0b7d2153b751169d0ae17648e117
--- firmware/App/Services/AlarmMgmt.h	(.../AlarmMgmt.h)	(revision 07a5add2dff254f7be3699e4efac2b99d3554847)
+++ firmware/App/Services/AlarmMgmt.h	(.../AlarmMgmt.h)	(revision 3e525c0567dd0b7d2153b751169d0ae17648e117)
@@ -186,6 +186,7 @@
     SW_FAULT_ID_PRES_OCCL_INVALID_STATE,
     SW_FAULT_ID_PRES_OCCL_INVALID_PRES_SENSOR,
     SW_FAULT_ID_PRES_OCCL_INVALID_OCCL_SENSOR,
+    SW_FAULT_ID_MSG_PENDING_ACK_LIST_FULL,                              // 50
     NUM_OF_SW_FAULT_IDS
 } SW_FAULT_ID_T;
 
Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r05b4d416b6bd5e7af4347f112a20f9f81a257064 -r3e525c0567dd0b7d2153b751169d0ae17648e117
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 05b4d416b6bd5e7af4347f112a20f9f81a257064)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 3e525c0567dd0b7d2153b751169d0ae17648e117)
@@ -49,7 +49,7 @@
 #define MAX_COMM_CRC_FAILURE_WINDOW_MS  (10 * SEC_PER_MIN * MS_PER_SECOND)
 
 #define MSG_NOT_ACKED_TIMEOUT_MS    ( MS_PER_SECOND * 1 )
-#define MSG_NOT_ACKED_MAX_RETRIES   5
+#define MSG_NOT_ACKED_MAX_RETRIES   3
 #define PENDING_ACK_LIST_SIZE       25
 
 #pragma pack(push,1)
@@ -788,15 +788,25 @@
             if ( message.crc == crc8( (U08*)(&message), sizeof(MESSAGE_HEADER_T) + message.msg.hdr.payloadLen ) )
             {
 #ifndef ACK_NOT_IMPLEMENTED
-                // if ACK,
+                // if ACK, mark pending message ACK'd
                 if ( MSG_ID_ACK == message.msg.hdr.msgID )
                 {
                     matchACKtoPendingACKList( message.msg.hdr.seqNo );
                 }
                 else
 #endif
                 {
-                    processReceivedMessage( &message.msg );
+#ifndef ACK_NOT_IMPLEMENTED
+                    // if received message requires ACK, queue one up
+                    if ( message.msg.hdr.seqNo < 0 )
+                    {
+                        sendACKMsg( &message.msg );
+                    }
+                    else
+#endif
+                    {   // otherwise, process the received message
+                        processReceivedMessage( &message.msg );
+                    }
                 }
             }
             else // CRC failed
@@ -988,14 +998,6 @@
 {
     U16 msgID = message->hdr.msgID;
 
-#ifndef ACK_NOT_IMPLEMENTED
-    // if received message requires ACK, queue one up
-    if ( message->hdr.seqNo < 0 )
-    {
-        sendACKMsg( message );
-    }
-#endif
-
     // handle any messages from other sub-systems
     switch ( msgID )
     {
Index: firmware/App/Services/SystemCommMessages.c
===================================================================
diff -u -r05b4d416b6bd5e7af4347f112a20f9f81a257064 -r3e525c0567dd0b7d2153b751169d0ae17648e117
--- firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 05b4d416b6bd5e7af4347f112a20f9f81a257064)
+++ firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 3e525c0567dd0b7d2153b751169d0ae17648e117)
@@ -99,7 +99,8 @@
  *************************************************************************/
 static U32 serializeMessage( MESSAGE_T msg, COMM_BUFFER_T buffer, BOOL ackReq )
 {
-    BOOL result;
+    BOOL result = 0;
+    BOOL error = FALSE;
     U32 msgSize = 0;
     U32 sizeMod, sizePad;
     U32 i;
@@ -153,13 +154,17 @@
     {
         if ( FALSE == addMsgToPendingACKList( &msg, buffer, data, msgSize ) )
         {
-            // TODO - ???
+            error = TRUE;
+            SET_ALARM_WITH_1_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_MSG_PENDING_ACK_LIST_FULL )
         }
     }
 #endif
 
-    // add serialized message data to appropriate out-going comm buffer
-    result = addToCommBuffer( buffer, data, msgSize );
+    if ( FALSE == error )
+    {
+        // add serialized message data to appropriate out-going comm buffer
+        result = addToCommBuffer( buffer, data, msgSize );
+    }
 
     return result;
 }
@@ -466,7 +471,7 @@
     // create a message record
     blankMessage( &msg );
     msg.hdr.msgID = MSG_ID_PRESSURE_OCCLUSION_DATA;
-    msg.hdr.payloadLen = sizeof( PERISTALTIC_PUMP_STATUS_PAYLOAD_T );
+    msg.hdr.payloadLen = sizeof( PRESSURE_OCCLUSION_DATA_T );
 
     payload.arterialPressure = artPres;
     payload.venousPressure = venPres;