AN2606 Datasheet, PDF (64/155 Pages) STMicroelectronics – STM32 microcontroller system memory boot mode

STM32F373xx devices bootloader
AN2606
Table 30. STM32F373xx configuration in System memory boot mode (continued)
Bootloader
Feature/Peripheral
State
Comment
USART2 bootloader
USART2
USART2_RX pin
Enabled
Input
Once initialized, the USART2 configuration
is: 8 bits, even parity and 1 Stop bit. The
USART2 uses its remapped pins.
PD6 pin: USART2 in reception mode
USART2_TX pin
Output
PD5 pin: USART2 in transmission mode
USB
Enabled
USB used in FS mode
DFU bootloader
USB_DM pin
USB_DP pin
Input/Output
PA11: USB DM line.
PA12: USB DP line
An external pull-up resistor 1.5 KOhm must
be connected to USB_DP pin.
Note:
The bootloader has two case of operation depending on the presence of the external clock
(HSE) at bootloader startup:
• If HSE is present and has a value of 24, 18, 16, 12, 9, 8, 6, 4 or 3 MHz, the system
clock is configured to 48 MHz with HSE as clock source. The DFU interface, USART1
and USART2 are functional and can be used to communicate with the bootloader
device.
• If HSE is not present, the HSI is kept as default clock source and only USART1 and
USART2 are functional.
The external clock (HSE) must be kept if it’s connected at bootloader startup because it will
be used as system clock source.
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