Fabless chip

Fixing STM32F746NGH6 Data Loss During Flash Writes

Title: Fixing STM32F746NGH6 Data Loss During Flash Writes

Fault Cause Analysis

Data loss during flash writes on the STM32F746NGH6 microcontroller can be caused by several factors. Understanding the root cause is essential in diagnosing and solving the issue. Common reasons for data loss during flash writes are:

Incorrect Flash Programming Sequence: STM32 microcontrollers, including the F746NGH6, require a specific sequence of operations to program or erase flash memory correctly. Missing or improper steps can result in incomplete or failed writes.

Power Supply Instability: If the microcontroller's power supply fluctuates or is unstable during a flash write operation, the data may not be written correctly. Flash memory requires a stable power supply to perform operations reliably.

Watchdog Timer Trigger: In some cases, the watchdog timer may be triggered during the flash write process if the MCU doesn’t respond to the timeout, potentially causing an unexpected reset or failure to write data.

Incorrect Timing : Flash writes to STM32 MCUs take some time to complete. If the system continues execution before the write is finished, the data may be corrupted. Flash writes must be carefully managed to avoid premature execution.

Write to Protected Flash Areas: Some areas of flash memory may be write-protected or locked, especially in secure bootloader regions or when certain flash sectors are set to be read-only. Trying to write to these regions can lead to failures.

Inadequate Error Handling: If the software doesn't properly handle errors during the flash write process, it could result in incomplete writes or data loss.

Possible Causes of the Issue: Timing-related issues during the write process (writing before the previous operation is finished). Power-related issues like voltage drops during the flash operation. Incorrect configuration or failure to unlock flash memory regions before writing. Faulty or missing interrupt handling (e.g., missing flash programming status check or interrupt). Step-by-Step Solution to Resolve Data Loss During Flash Writes

Here’s a systematic approach to resolve data loss issues during flash writes:

Step 1: Ensure Correct Flash Programming Sequence

The STM32F746NGH6 requires a well-defined sequence for flash writes, which includes:

Unlocking the flash memory for write access. Ensuring that the flash memory is not in read-only mode or locked. Checking the flash status to confirm that the write operation can proceed.

Solution: Ensure that your software follows the correct sequence as per the STM32 HAL (Hardware Abstraction Layer) or direct register-level programming:

Unlock the flash memory (via FLASH_Unlock() function). Check the FLASH_SR register for the status of the flash memory before starting the write operation. Set the PG bit in the FLASH_CR register to begin the write.

Step 2: Check Power Supply Stability

Flash write operations require a stable power supply to avoid data corruption.

Solution: Use a stable voltage regulator with minimal ripple to ensure the microcontroller's voltage remains steady during the write process. If you're working in an environment with fluctuating power, consider adding capacitor s near the power pins of the MCU or using a backup power source (like a battery or capacitor) during writes.

Step 3: Handle Watchdog Timer Properly

If your system uses a watchdog timer, ensure that the watchdog is either disabled or properly reset during flash writes to prevent an unintended reset that could interrupt the process.

Solution: Disable the watchdog timer during flash writes by calling IWDG_Stop() or ensure the watchdog is properly reset before and after each flash write operation.

Step 4: Ensure Flash Write Timing Is Managed Correctly

The STM32 flash memory requires time to complete each write operation. If the MCU executes code that attempts to write to the flash memory before the operation finishes, data corruption can occur.

Solution: After starting a flash write, check the BUSY flag in the FLASH_SR register to ensure the operation is complete before initiating a new write. A typical implementation would look like this:

while (FLASH->SR & FLASH_SR_BSY); // Wait for the flash to become ready

This ensures that the write operation is completed before proceeding.

Step 5: Verify Write Protection

Some regions of the flash memory may be protected to prevent accidental writes. Ensure that the area you are trying to write to is not write-protected.

Solution: If necessary, disable the write protection by unlocking the appropriate flash sectors using the FLASH_OB_Unlock() function and enabling the write protection with FLASH_OB_Launch() once you’re done.

Step 6: Implement Proper Error Handling

Flash write operations can fail due to various reasons (e.g., invalid address, incorrect sequence). Implement proper error checking to handle any failures during the write process.

Solution: Use FLASH_SR to check for errors after each write. Common error flags include FLASH_SR_PGAERR, FLASH_SR_PGPERR, and FLASH_SR_WRPERR. Handle these errors in your code to ensure the system behaves appropriately in case of failures.

Example:

if (FLASH->SR & FLASH_SR_PGAERR) { // Handle Programming Alignment error } if (FLASH->SR & FLASH_SR_PGPERR) { // Handle Programming Parallelism error } if (FLASH->SR & FLASH_SR_WRPERR) { // Handle Write Protection error }

Step 7: Test and Validate

Once the above steps are implemented, perform thorough testing under various conditions to ensure that the data loss issue is resolved. Test with different data sizes, under load, and across different power conditions.

Conclusion:

By following the steps above, you can systematically address the issue of data loss during flash writes on the STM32F746NGH6. The key areas to focus on are proper sequence and timing of flash operations, stable power supply, handling of the watchdog timer, and ensuring error handling and write protection are appropriately managed. With this approach, you can ensure reliable flash writing without data loss.