This is a RTC additional function. This is only for Nucleo F401RE & F411RE mbed(Added L152RE, F334R8, L476RG & F746xx). If you connected battery backup circuit for internal RTC, you can make a power-off and reset condition. RTC still has proper time and date.

Dependents:   Nucleo_rtos_sample PB_Emma_Ethernet

Please refer following NOTE information.
/users/kenjiArai/notebook/nucleo-series-rtc-control-under-power-onoff-and-re/

Revision:
12:4074fe3e67c7
Parent:
8:88d30761683b
--- a/modify_info_L152.h	Sat May 23 22:22:32 2015 +0000
+++ b/modify_info_L152.h	Fri Jan 29 07:35:34 2016 +0000
@@ -2,11 +2,11 @@
  * mbed Application program
  *      Library differ part (This is only information document)
  *
- * Copyright (c) 2015 Kenji Arai / JH1PJL
+ * Copyright (c) 2015,'16 Kenji Arai / JH1PJL
  *  http://www.page.sannet.ne.jp/kenjia/index.html
  *  http://mbed.org/users/kenjiArai/
  *      Created: January   23rd, 2015
- *      Revised: Feburary  16th, 2015
+ *      Revised: January   30th, 2016
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
  * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
@@ -19,9 +19,9 @@
 //      rtc_api.c -> rtc_api_L152.c
 //*************************************************************************************************
 //
-// (1) Update mbed-src library if you want
+// (1) Update mbed-dev library if you want
 // (2) File rtc_api_L152.c copy to directry
-//     /mbed-src/targets/hal/TARGET_STM/TARGET_STM32L1/
+//     /mbed-dev/targets/hal/TARGET_STM/TARGET_STM32L1/
 // (3) Delete rtc_api.c in the same directory
 // (4) Edit rtc_api_L152.c
 //      (a)Delete 1st line