AN2606 datasheet(35/155 Pages) STMICROELECTRONICS

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AN2606

STM32L1xxxC devices bootloader

154

STM32L1xxxC devices bootloader

8.1

Bootloader configuration

The STM32L1xxxC bootloader is activated by applying pattern1 (described in Table 2:

Bootloader activation patterns). The following table shows the hardware resources used by

this bootloader.

Table 14. STM32L1xxxC configuration in System memory boot mode

Bootloader

Feature/Peripheral

State

Comment

Common to all

bootloaders

RCC

HSI enabled

The system clock frequency is 16 MHz

using the HSI. This is used only for

USART1 and USART2 bootloaders and

during USB detection for DFU bootloader

(once the DFU bootloader is selected, the

clock source is derived from the external

crystal).

HSE enabled

The external clock is mandatory only for the

DFU bootloader and must be in the

following range:

[24, 16, 12, 8, 6, 4, 3, 2] MHz.

The PLL is used to generate the USB

48 MHz clock and the 32 MHz clock for the

system clock.

The Clock Security System (CSS) interrupt

is enabled for the DFU bootloader. Any

failure (or removal) of the external clock

generates a system reset.

IWDG

The independent watchdog (IWDG)

prescaler is configured to its maximum

value and is periodically refreshed to

prevent watchdog resets (in case the

hardware IWDG option was previously

enabled by the user).

Power

Voltage range is set to Voltage Range 1.

System memory

8 Kbytes starting from address

0x1FF0 0000. This area contains the

bootloader firmware.

RAM

4 Kbytes starting from address 0x20000000

are used by the bootloader firmware.

USART1 bootloader

USART1

Enabled

Once initialized, the USART1 configuration

is 8 bits, even parity and 1 stop bit.

USART1_RX pin

Input

PA10 pin: USART1 in reception mode

USART1_TX pin

Output

PA9 pin: USART1 in transmission mode

USART1 and

USART2 bootloaders

SysTick timer

Enabled

Used to automatically detect the serial baud

rate from the host for the USARTx

bootloader.

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