Index: firmware/App/Modes/BloodPrime.c
===================================================================
diff -u -rc1b9ac0dbf2196280895d2e440dd7ac288ac8424 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/BloodPrime.c	(.../BloodPrime.c)	(revision c1b9ac0dbf2196280895d2e440dd7ac288ac8424)
+++ firmware/App/Modes/BloodPrime.c	(.../BloodPrime.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -139,6 +139,7 @@
     setBloodPumpTargetFlowRate( (U32)bloodPrimeRampFlowRate_mL_min, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_OPEN_LOOP );
     setDialInPumpTargetFlowRate( DIALYSATE_FLOW_RATE_FOR_RECIRC, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
     cmdStartDGTrimmerHeater();
+    setCurrentSubState( NO_SUB_STATE );
 
     // Start air trap control
     startAirTrapControl();
Index: firmware/App/Modes/ConsumableSelfTest.c
===================================================================
diff -u -rce64b7e15824641a6a6465c28eec5d8ec593f110 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/ConsumableSelfTest.c	(.../ConsumableSelfTest.c)	(revision ce64b7e15824641a6a6465c28eec5d8ec593f110)
+++ firmware/App/Modes/ConsumableSelfTest.c	(.../ConsumableSelfTest.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -72,6 +72,7 @@
     signalDialInPumpHardStop();
     signalDialOutPumpHardStop();
     stopSyringePump();
+    setCurrentSubState( (U32)currentConsumableSelfTestState );
 
     // Set valves to default positions
     setValveAirTrap( STATE_CLOSED );
@@ -159,6 +160,7 @@
     if ( priorSubState != currentConsumableSelfTestState )
     {
         setCurrentSubState( (U32)currentConsumableSelfTestState );
+        SEND_EVENT_WITH_2_U32_DATA( HD_EVENT_SUB_STATE_CHANGE, priorSubState, currentConsumableSelfTestState );
     }
     // Handle triggered alarm with stop property
     handleConsumableSelfTestStopRequest();
Index: firmware/App/Modes/Dialysis.c
===================================================================
diff -u -rce64b7e15824641a6a6465c28eec5d8ec593f110 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision ce64b7e15824641a6a6465c28eec5d8ec593f110)
+++ firmware/App/Modes/Dialysis.c	(.../Dialysis.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -792,7 +792,6 @@
 
     if ( priorSubState != currentUFState )
     {
-        setCurrentSubState( (U32)currentUFState );
         SEND_EVENT_WITH_2_U32_DATA( HD_EVENT_SUB_STATE_CHANGE, priorSubState, currentUFState );
     }
 
@@ -839,7 +838,6 @@
 
     if ( priorSubState != currentSalineBolusState )
     {
-        setCurrentSubState( (U32)currentSalineBolusState );
         SEND_EVENT_WITH_2_U32_DATA( HD_EVENT_SUB_STATE_CHANGE, priorSubState, currentSalineBolusState );
     }
 
Index: firmware/App/Modes/ModePostTreat.c
===================================================================
diff -u -rce64b7e15824641a6a6465c28eec5d8ec593f110 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/ModePostTreat.c	(.../ModePostTreat.c)	(revision ce64b7e15824641a6a6465c28eec5d8ec593f110)
+++ firmware/App/Modes/ModePostTreat.c	(.../ModePostTreat.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -153,7 +153,7 @@
     signalBloodPumpHardStop();
     signalDialOutPumpHardStop();
     signalDialInPumpHardStop();
-    setCurrentSubState( NO_SUB_STATE );
+    setCurrentSubState( currentPostTreatmentState );
     collectTreatmentLogData();
 
     exitBloodLeakNormalState();
@@ -370,6 +370,7 @@
         // Done with draining the reservoirs
         state = HD_POST_TREATMENT_PATIENT_DISCONNECTION_STATE;
         doorClosedRequired( TRUE, TRUE );
+        setCurrentSubState( NO_SUB_STATE );
     }
 
     return state;
Index: firmware/App/Modes/ModePreTreat.c
===================================================================
diff -u -rce64b7e15824641a6a6465c28eec5d8ec593f110 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision ce64b7e15824641a6a6465c28eec5d8ec593f110)
+++ firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -221,7 +221,6 @@
     signalDialInPumpHardStop();
     signalDialOutPumpHardStop();
     stopSyringePump();
-    setCurrentSubState( NO_SUB_STATE );
 
     // Set valves to default positions
     setValveAirTrap( STATE_CLOSED );
@@ -790,6 +789,7 @@
         {
             submodeCompleteTransitionTimeCounter = 0;
             state = HD_PRE_TREATMENT_CART_INSTALL_STATE;
+            setCurrentSubState( NO_SUB_STATE );
             transitionToCartridgeInstallation();
         }
     }
Index: firmware/App/Modes/ModeTreatmentParams.c
===================================================================
diff -u -rce64b7e15824641a6a6465c28eec5d8ec593f110 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/ModeTreatmentParams.c	(.../ModeTreatmentParams.c)	(revision ce64b7e15824641a6a6465c28eec5d8ec593f110)
+++ firmware/App/Modes/ModeTreatmentParams.c	(.../ModeTreatmentParams.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -137,7 +137,7 @@
     treatmentCancelled = FALSE;
 
     setTreatmentParameterF32( TREATMENT_PARAM_UF_VOLUME, 0.0 );
-
+    setCurrentSubState( NO_SUB_STATE );
     // Set user alarm recovery actions allowed in this mode
     setAlarmUserActionEnabled( ALARM_USER_ACTION_RESUME, FALSE );
     setAlarmUserActionEnabled( ALARM_USER_ACTION_RINSEBACK, FALSE );
@@ -282,8 +282,6 @@
     HD_TREATMENT_PARAMS_MODE_STATE_T priorSubState = currentTreatmentParamsState;
     BOOL stop = isStopButtonPressed();
 
-    setCurrentSubState( NO_SUB_STATE );
-
     if ( TRUE == stop )
     {
         // Ignore stop button in this mode.
@@ -306,6 +304,11 @@
 
     }
 
+    if ( priorSubState != currentTreatmentParamsState )
+    {
+        SEND_EVENT_WITH_2_U32_DATA( HD_EVENT_SUB_MODE_CHANGE, priorSubState, currentTreatmentParamsState );
+    }
+
     return (U32)currentTreatmentParamsState;
 }
 
Index: firmware/App/Modes/OperationModes.c
===================================================================
diff -u -r0e0fc7fbbc571a76deb8ddc6e6382bfa58598406 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/OperationModes.c	(.../OperationModes.c)	(revision 0e0fc7fbbc571a76deb8ddc6e6382bfa58598406)
+++ firmware/App/Modes/OperationModes.c	(.../OperationModes.c)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -578,28 +578,42 @@
     return new_id;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The setCurrentSubState function sets the current subState.
+ * @details Inputs: subState
+ * @details Outputs: currentSubState
+ * @param subState the enumerated sub state.
+ * @return none
+ *************************************************************************/
 void setCurrentSubState( U32 subState )
 {
     currentSubState = subState;
 }
 
-static void sendOperationStatusEvent( void )
+/*********************************************************************//**
+ * @brief
+ * The sendOperationStatusEvent function constructs and sends an HD operation
+ * status event.
+ * @details Inputs: currentMode, currentSubMode, currentSubState
+ * @details Outputs: dat1, dat2.
+ * @param none
+ * @return none
+ *************************************************************************/
+static void sendOperationStatusEvent()
 {
 
     EVENT_DATA_T dat1;
     EVENT_DATA_T dat2;
-    OP_STATUS_EVENT_PAYLOAD_T opData;
+    U32 opData = ( (U08)currentMode +
+                 ( (U08)currentSubMode << SHIFT_8_BITS_FOR_BYTE_SHIFT ) +
+                 ( (U08)currentSubState << SHIFT_16_BITS_FOR_WORD_SHIFT ) );
 
     dat2.dataType = EVENT_DATA_TYPE_U32;
     dat2.data.uInt.data = 0;
 
-    opData.OpStatus[OPERATION_MODE] = (U08)currentMode;
-    opData.OpStatus[SUB_MODE] = (U08)currentSubMode;
-    opData.OpStatus[SUB_STATE] = (U08)currentSubState;
-    opData.OpStatus[RESERVED] = 0;
-
     dat1.dataType = EVENT_DATA_TYPE_U32;
-    dat1.data.uInt.data = (U32)(opData);
+    dat1.data.uInt.data = opData;
 
     sendEvent( HD_EVENT_OPERATION_STATUS, dat1, dat2 );
 }
Index: firmware/App/Modes/OperationModes.h
===================================================================
diff -u -r0e0fc7fbbc571a76deb8ddc6e6382bfa58598406 -r35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1
--- firmware/App/Modes/OperationModes.h	(.../OperationModes.h)	(revision 0e0fc7fbbc571a76deb8ddc6e6382bfa58598406)
+++ firmware/App/Modes/OperationModes.h	(.../OperationModes.h)	(revision 35a326b0f9f2fd83bac4be54e67ebde2d3f2c7e1)
@@ -40,24 +40,6 @@
     U32 subMode;                         ///< Current sub-mode of current operating mode
 } OP_MODE_PAYLOAD_T;
 
-/// Payload record structure for operation status events.
-typedef enum Op_Status_Fields
-{
-  OPERATION_MODE = 0,                   ///< Current Operation mode
-  SUB_MODE,                             ///< Current sub mode
-  SUB_STATE,                            ///< Current sub state where applicable
-  RESERVED,                             ///< Reserved 8-bit space used to uphold 32-bit payload sizes.
-  NUM_OF_OP_STATUS_TYPE
-} OP_STATUS_T;
-
-#pragma pack(push, 1)
-
-typedef struct
-{
-    U08 OpStatus[NUM_OF_OP_STATUS_TYPE];
-} OP_STATUS_EVENT_PAYLOAD_T;
-
-#pragma pack(pop)
 // ********** public function prototypes **********
 
 void initOperationModes( void );                                    // Initialize this module