OTP programming window

The OTP window is available exclusively for MPUs and STM32N6 devices. It extracts the OTP partition [ID 0xF2] using the STMPRGFW-UTIL interface to read, display, and fuse the OTP registers.

STM32MP1xx devices have 3072 OTP (one-time programmable) bits, which can be read-accessed in 96 words: OTPx with x = 0 to 95. STM32MP2xx and STM32N6 devices have 368 words: OTPx with x = 0 to 367.

Some OTP words are programmed during manufacturing for product differentiation or keys.

Note

The OTP window is accessible through USB/UART interfaces for STM32MP. For STM32N6 it is available via Debug/USB/UART interfaces.

The UI has six main goals:

1. Get OTP structure information.

2. Read and display words in table view format.

3. Edit and fuse OTP registers.

4. Lock specific or all words.

5. Program binary files, frequently for key fuse operations.

6. Save the OTP partition in an output binary file for debug.

Open the OTP window by pressing the OTP button from the main window to start reading the OTP partition. When this is correctly executed, the words are displayed in table view.

Fig. 95 OTP MPU window

Get OTP structure information

This section displays an overview of the connected device.

• Structure version.

• Global state.

• State: Secure open / Secure closed / Invalid.

Note

The OTP UI is available only for structure version 2.

Read and display words

After checking the OTP partition, the tool decodes and shows the words in table view format including the following columns:

• Name: OTP word name.

• Word: OTP word ID as a tree component.

• Value: hexadecimal value, shown in red for locked words, as editable field.

• Status: hexadecimal value.

• Lock: indicates the lock state of the considered word as a checkbox component. It is checked if the item is locked, otherwise it is unchecked. The column is disabled if the item is in permanent write lock state.

• Description: decodes the status of the OTP word and displays a brief description for children items.

Note

Press the Read button to refresh all table fields or discard changes.

Edit and fuse words

It is possible to directly edit the Value table cell to write a new value. Press Enter after each change. The tool verifies the syntax of the input item to respect hexadecimal format and item width, then it checks the locking state of the current item before starting fusing.

Fig. 96 Edit denial for locked words

After modification, press the Apply button and confirm the operation to start the update and refresh the table view.

Fig. 97 Program Apply confirmation

Lock specific/all words

The lock operation allows the user to close write programming against any modification of the considered OTP word. It is possible to lock several words in one shot by setting the assigned checkboxes, then clicking Apply to start the operation.

Note

To go faster to the initial OTP lock state, it is recommended to press the Read button.

It is possible to lock all words at once by setting the Lock all checkbox. A message pops up asking to confirm the start of the procedure, which results in all words being closed and no further changes allowed.

Fig. 98 Lock all words confirmation

If the operation is successful, the table view is disabled for all Lock columns.

Program binary file

This section contains different graphical components needed to program a binary file on the OTP registers starting from a word ID, based on the following steps:

1. Choose the adequate binary file with .bin extension by clicking

   Browse.

2. Mention the start word ID in decimal format from 0 to 95.

3. Check or uncheck the Lock region checkbox to indicate the operation

   type, update or permanent write lock.

4. Press the Program button to start the download flow.

If the procedure is completed correctly, an informational dialog appears to confirm that the operation is completed.

Note

The input binary is a 32-bit aligned file. The tool adds padding values if the file is not aligned, and a warning message is displayed in the log panel.

Fig. 99 Download binary file

Save OTP partition

The user can save the whole current OTP partition in a binary file with .bin extension, which can be used for future analysis or to archive the current device configuration.

Press Save OTP partition and choose the desired output name and directory. If the save is completed correctly, an informational dialog appears to confirm that the operation is completed.

Fig. 100 Save OTP partition

Note

The size of the output file must be 1024 bytes. U-Boot program must be installed before launching the OTP window, which is necessary to expose the OTP partition. Words 32 to 95 do not have child fields, can be edited only once, and must be permanently locked after programming. Word editing and lock operation can be performed at the same time after clicking Apply.