Table 7. Bootloader Interfaces - ST STM32L1 Series Application Note

AN4612
nBOOT1
FLASH_OPTR
[23]
0
0
1
1
1. A Flash empty check mechanism is implemented to force the boot from system Flash if the first Flash
memory location is not programmed (0xFFFF FFFF) and if the boot selection was configured to boot from
the main Flash.
Embedded bootloader
The embedded bootloader is located in the system memory, programmed by ST during
production. It is used to reprogram the Flash memory using one of the following serial
interfaces:
Peripheral
DFU
USART1
USART2
USART2
USART3
I2C1
I2C2
Table 6. Boot modes for STM32L4 Cat. 4 devices (continued)
nBOOT0
BOOT0 pin
FLASH_OPTR
[27]
x
0
x
0

Table 7. Bootloader interfaces

Pin
USB_DM (PA11)
USB_DP (PA12)
USART1_TX (PA9)
USART1_RX (PA10)
USART2_TX (PD5)
USART2_RX (PD6)
USART2_TX (PA2)
USART2_RX (PA3)
USART3_TX (PC10)
USART3_RX (PC11)
I2C1_SCL (PB6)
I2C1_SDA (PB7)
I2C2_SCL (PB10)
I2C2_SDA (PB11)
DocID027094 Rev 3
nSWBOOT0
FLASH_OPTR
PH3
[26]
1 1
x 0
1 1
x 0
Boot mode selection
Main Flash Boot Memory
(1)
empty Space Alias
Embedded
x
selected as
Embedded
x
selected as
x
selected as
x
selected as
STM32L1 STM32L4
X
X
X
-
-
-
-
SRAM1 is
boot area
SRAM1 is
boot area
System
memory is
boot area
System
memory is
boot area
X
X
-
X
X
X
X
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