/**
  @page ExternalTrigger_Synchro TIM External Trigger Synchro example
  
  @verbatim
  ******************** (C) COPYRIGHT 2012 STMicroelectronics *******************
  * @file    TIM/ExternalTrigger_Synchro/readme.txt 
  * @author  MCD Application Team
  * @version V1.1.1
  * @date    13-April-2012
  * @brief   Description of the TIM External Trigger Synchro example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
   @endverbatim

@par Example Description 

This example shows how to synchronize TIM peripherals in cascade mode with an
external trigger.
In this example three timers are used:

1/TIM9 is configured as Master Timer:
  - Toggle Mode is used
  - The TIM9 Enable event is used as Trigger Output 

2/TIM9 is configured as Slave Timer for an external Trigger connected to TIM9 
  TI2 pin (TIM9 CH2 configured as input pin):
  - The TIM9 TI2FP2 is used as Trigger Input
  - Rising edge is used to start and stop the TIM9: Gated Mode.

3/TIM3 is slave for TIM9 and Master for TIM4,
  - Toggle Mode is used
  - The ITR0(TIM9) is used as input trigger 
  - Gated mode is used, so start and stop of slave counter
    are controlled by the Master trigger output signal(TIM9 enable event).
  - The TIM3 enable event is used as Trigger Output. 

4/TIM4 is slave for TIM3,
  - Toggle Mode is used
  - The ITR2(TIM3) is used as input trigger
  - Gated mode is used, so start and stop of slave counter
    are controlled by the Master trigger output signal(TIM3 enable event).

  * For Low-density, Medium-density, High-density and Connectivity line devices:
    The TIMxCLK is fixed to 32 MHZ, the Prescaler is equal to 2 so the TIMx clock 
    counter is equal to 16 MHz.
    The Three Timers are running at: 
    TIMx frequency = TIMx clock counter/ 2*(TIMx_Period + 1) = 72.1 KHz.

The starts and stops of the TIM9 counters are controlled by the external trigger.
The TIM3 starts and stops are controlled by the TIM9, and the TIM4 starts and 
stops are controlled by the TIM3.  

@par Directory contents 

  - TIM/ExternalTrigger_Synchro/stm32l1xx_conf.h         Library Configuration file
  - TIM/ExternalTrigger_Synchro/stm32l1xx_it.c           Interrupt handlers
  - TIM/ExternalTrigger_Synchro/stm32l1xx_it.h           Interrupt handlers header file
  - TIM/ExternalTrigger_Synchro/main.c                   Main program 
  - TIM/ExternalTrigger_Synchro/system_stm32l1xx.c       STM32L1xx system source file
  
@note The "system_stm32l1xx.c" is generated by an automatic clock configuration 
      system and can be easily customized to your own configuration. 
      To select different clock setup, use the "STM32L1xx_Clock_Configuration_V1.1.0.xls" 
      provided with the AN3309 package available on <a href="http://www.st.com/internet/mcu/family/141.jsp">  ST Microcontrollers </a>

@par Hardware and Software environment 

  - This example runs on STM32L1xx Ultra Low Power High-, Medium-Density and Medium-Density Plus Devices.
  
  - This example has been tested with STMicroelectronics STM32L152D-EVAL (STM32L1xx 
    Ultra Low Power High-Density) and STM32L152-EVAL (STM32L1xx Ultra Low 
    Power Medium-Density) evaluation board and can be easily tailored to any 
    other supported device and development board.

  - STM32L152-EVAL and STM32L152D-EVAL Set-up 
    - Connect an external trigger, with a frequency <=  xx KHz, to the TIM9 CH2 
      pin (PA.03). In this example the frequency is equal to x KHz.
      
    - Connect the following pins to an oscilloscope to monitor the different 
      waveforms:
        - TIM9 CH1 (PA.02) 
        - TIM3 CH1 (PA.06)
        - TIM4 CH1 (PB.6)  
        
@par How to use it ? 

In order to make the program work, you must do the following :
 - Copy all source files from this example folder to the template folder under
   Project\STM32L1xx_StdPeriph_Templates
 - Open your preferred toolchain 
 - Rebuild all files and load your image into target memory
 - Run the example

@note
- Ultra Low Power Medium-density devices are STM32L151xx and STM32L152xx 
  microcontrollers where the Flash memory density ranges between 64 and 128 Kbytes.
- Ultra Low Power Medium-density Plus devices are STM32L151xx, STM32L152xx and 
  STM32L162xx microcontrollers where the Flash memory density is 256 Kbytes.
- Ultra Low Power High-density devices are STM32L151xx, STM32L152xx and STM32L162xx 
  microcontrollers where the Flash memory density is 384 Kbytes.  
   
 * <h3><center>&copy; COPYRIGHT STMicroelectronics</center></h3>
 */


