/**
@page FMC_SDRAM_LowPower SDRAM memory low power mode use example
@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file FMC/FMC_SDRAM_LowPower/readme.txt
* @author MCD Application Team
* @brief Description of the FMC SDRAM Low power example.
******************************************************************************
*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
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* 3. Neither the name of STMicroelectronics nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
@endverbatim
@par Example Description
This example describes how to configure the FMC controller to access the SDRAM
memory in low power mode (SDRAM Self Refresh mode).
This example guides you through the different configuration steps by mean of HAL API
to drive the MT48LC4M32B2B5-7 SDRAM memory mounted on STM324x9I-EVAL RevB board, in
low power mode (SDRAM Self Refresh mode).
It gives a simple application of the FMC SDRAM low power mode use (self refresh mode)
while the MCU is in a low power mode (STOP mode).
At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK) to run at 180 MHz.
The purpose is to show how the SDRAM can retain data written after entering STOP mode.
STOP mode is a CPU low power mode which stops all peripherals clocks in the 1.2V
domain. Only internal SRAM and registers content are preserved in this mode.
After SDRAM initialization, the data is written to the memory and a "self refresh"
command is sent to the SDRAM. The program waits for TAMPER/KEY button to be pushed
to enter the CPU in STOP mode, the LED4 is then turned ON.
The wake-up from STOP mode is done when pushing WAKEUP Button and the CPU returns
to RUN mode. At this time, the system clock is reconfigured using the function
SystemClock_Config().
Finally, a "normal mode" command is send to SDRAM memory to exit self refresh mode.
The data written to SDRAM is read back and checked.
LEDs are used to indicate the system state as following:
- LED4 ON: CPU enters STOP mode.
- LED4 OFF: the CPU is in RUN mode.
- LED1 ON: correct data transfer (PASS).
- LED2 ON: incorrect data transfer (FAIL).
@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
@note The application needs to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.
@par Keywords
Memory, FMC, SDRAM, Read, Write, Initialization, Access, Low power, Self Refresh, Stop mode
@par Directory contents
- FMC/FMC_SDRAM_LowPower/Inc/stm32f4xx_hal_conf.h Library Configuration file
- FMC/FMC_SDRAM_LowPower/Inc/stm32f4xx_it.h Interrupt handlers header file
- FMC/FMC_SDRAM_LowPower/Inc/main.h Main program header file
- FMC/FMC_SDRAM_LowPower/Src/main.c Main program
- FMC/FMC_SDRAM_LowPower/Src/stm32f4xx_it.c Interrupt handlers
- FMC/FMC_SDRAM_LowPower/Src/system_stm32f4xx.c STM32F4xx system clock configuration file
@par Hardware and Software environment
- This example runs on STM32F429xx/STM32F439xx devices.
- This example has been tested with STMicroelectronics STM324x9I-EVAL RevB
evaluation boards and can be easily tailored to any other supported device
and development board.
@par How to use it ?
In order to make the program work, you must do the following :
- Open your preferred toolchain
- Rebuild all files and load your image into target memory
- Run the example
* <h3><center>© COPYRIGHT STMicroelectronics</center></h3>
*/
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