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:
1:3129de8d50ea
diff -r e4c20fd769f1 -r 3129de8d50ea modify_info_L152.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modify_info_L152.h	Sat Feb 14 11:31:51 2015 +0000
@@ -0,0 +1,28 @@
+/*
+ * mbed Application program
+ *      Library differ part (This is only information document)
+ *
+ * Copyright (c) 2015 Kenji Arai / JH1PJL
+ *  http://www.page.sannet.ne.jp/kenjia/index.html
+ *  http://mbed.org/users/kenjiArai/
+ *      Created: January   23rd, 2015
+ *      Revised: Feburary  14th, 2015
+ *
+ * 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
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+//*************************************************************************************************
+//  Replace following files in the library
+//      rtc_api.c -> rtc_api_L152.c
+//*************************************************************************************************
+//
+// (1) Update mbed-src library if you want
+// (2) File rtc_api_L152.c copy to directry /mbed-src/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/
+// (3) Delete rtc_api.c in the same directory
+// (4) Edit rtc_api_L152.c
+//      (a)Delete 1st line
+//      (b)Delete last line
+//