Index: sources/update/MsgLink.h
===================================================================
diff -u -r7cf31f6cfef97bb564a103c263821a3b722c8a2b -r2ee835c4c687263fd8852a431db1223cc0e8055c
--- sources/update/MsgLink.h	(.../MsgLink.h)	(revision 7cf31f6cfef97bb564a103c263821a3b722c8a2b)
+++ sources/update/MsgLink.h	(.../MsgLink.h)	(revision 2ee835c4c687263fd8852a431db1223cc0e8055c)
@@ -61,6 +61,13 @@
  */
 const std::chrono::duration<int, std::milli> g_ms_pause(20);
 
+/*!
+ * \brief Convert ACK value to milliseconds.
+ *
+ * 0=NACK 1= ACK no wait, else ms = (ack-1)*scale.
+ */
+const uint32 gAckSleepScale = 200;
+
 /*! 
  * This is 2x the line speed transfer of a 
  * message relative to kbps of the line in milliseconds. 
@@ -149,6 +156,9 @@
         // We are expecting data.
         _expecting = true;
 
+        // Default no extra sleep.
+        _extraSleep = 0;
+
         _wasData =
             (msgId == SwUpdateCanMsgIds::DataBufferId_HD_FW)   ||
             (msgId == SwUpdateCanMsgIds::DataBufferId_HD_FPGA) ||
@@ -189,8 +199,11 @@
             this->sendPacket(msgId, msg, length);
             
             // Wait to either retry or success.
-            if (_ew.wait()) {
+            if (_ew.wait()) {                
                 _expecting = false;
+                if (_extraSleep != 0) {
+                    _ew.sleep(_extraSleep);
+                }
                 return true;
             }
             _retries++;
@@ -277,13 +290,22 @@
                     //   T         T           F      |  F  For the thread not an ack.
                     //   T         T           T      |  T  For this thread and an ack.          
                     if (msgId == SwUpdateCanMsgIds::ResponseId) {                          
-                        SwUpdateResponse *resp = (SwUpdateResponse *)pData;                
+                        SwUpdateResponse *resp = (SwUpdateResponse *)pData;
+                        if (resp->id == _msgIdSlot) {
+                            if (resp->ackNack >= 1) {
+                                rv = true;
+                                if (resp->ackNack != 1) {
+                                    _extraSleep = (uint16_t)(resp->ackNack * gAckSleepScale);
+                                }
+                            }
+                        }
                         rv = ((resp->id == _msgIdSlot) && (resp->ackNack == 1));
                     } else {
                         rv = true;
                     }            
                 }
             }
+
             // It's good? fire event.
             if (rv) {
                 _ew.fireEvent();
@@ -298,6 +320,7 @@
     uint32      _retries;       ///< Total number of retries.
     uint16      _expectedId;    ///< Expected message Id.
     uint8       _msgIdSlot;     ///< Message slot.
+    uint16      _extraSleep;    ///< Extra sleep request from FW.
 
     bool                _wasData;   ///< Was data.
     SwUpdateDataBuffer  _dataBuf;   ///< Data buffer.