Message Sequence Charts added

README.md

@@ -93,6 +93,24 @@ or inform that there are no pending messages.
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ```
 
+# Message Sequence Flow Charts
+
+## Time request
+
+![time-request.png](/img/time-request.png)
+
+## Data send (no pending messages)
+
+![data-send-(no-pending-messages).png](/img/data-send-(no-pending-messages).png)
+
+## Data send (pending message)
+
+![data-send-(pending-message).png](/img/data-send-(pending-message).png)
+
+## Check for a pending message
+
+![check-for-a-pending-message.png](/img/check-for-a-pending-message.png)
+
 # Packet type values
 
 ```