AN2606 datasheet(21/155 Pages) STMICROELECTRONICS

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AN2606

General bootloader description

154

Figure 5. CAN Connection

Note:

When a bootloader firmware supports DFU, it is mandatory that no USB Host is connected

to the USB peripheral during the selection phase of the other interfaces. After selection

phase, the user can plug a USB cable without impacting the selected bootloader execution

except commands which generate a system reset.

It is recommended to keep the RX pins of unused Bootloader interfaces (USART_RX,

SPI_MOSI, CAN_RX and USB D+/D- lines if present) at a known (low or high) level at the

startup of the Bootloader (detection phase). Leaving these pins floating during the detection

phase might lead to activating unused interface.

3.4

Bootloader Memory Management

All write operations using bootloader commands must only be Word-aligned (the address

should be a multiple of 4). The number of data to be written must also be a multiple of 4

bytes (non-aligned half page write addresses are accepted).

Some products embed a bootloader that has some specific features:

•

Some products don’t support Mass erase operation. To perform a mass erase

operation using bootloader, two options are available:

–

Erase all sectors one by one using the Erase command

–

Set protection level to Level 1. Then, set it to Level 0 (using the Read protect

command and then the Read Unprotect command). This operation results in a

mass erase of the internal Flash memory.

•

Bootloader firmware of STM32 L1 and L0 series supports Data Memory in addition to

standard memories (internal Flash, internal SRAM, option bytes and System memory).

The start address and the size of this area depend on the product, please refer to

product reference manual for more information. Data memory can be read and written

but cannot be erased using the Erase Command. When writing in a Data memory

location, the bootloader firmware manages the erase operation of this location before

any write. A write to Data memory must be Word-aligned (address to be written should

be a multiple of 4) and the number of data must also be a multiple of 4. To erase a Data

memory location, you can write zeros at this location.

•

Bootloader firmware of STM32 F2, F4 and L4 series supports OTP memory in addition

to standard memories (internal Flash, internal SRAM, option bytes and System

memory). The start address and the size of this area depend on the product, please

refer to product reference manual for more information. OTP memory can be read and

written but cannot be erased using Erase command. When writing in an OTP memory

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