Boot Configuration; Boot Mode Selection; Boot Pin Connection; Table - ST STM32F20 Series Application Note

Boot configuration

3 Boot configuration
3.1

Boot mode selection

In the STM32F20xxx/21xxx, three different boot modes can be selected by means of the
BOOT[1:0] pins as shown in

Table 1.

BOOT mode selection pins
BOOT1
x
0
1
The values on the BOOT pins are latched on the 4
is up to the user to set the BOOT1 and BOOT0 pins after reset to select the required boot
mode.
The BOOT pins are also resampled when exiting the Standby mode. Consequently, they
must be kept in the required Boot mode configuration in the Standby mode. After this startup
delay has elapsed, the CPU fetches the top-of-stack value from address 0x0000 0000, and
starts code execution from the boot memory starting from 0x0000 0004.
3.2

Boot pin connection

Figure 10
STM32F20xxx/21xxx.

Figure 10. Boot mode selection implementation example

1. Resistor values are given only as a typical example.
16/29
Table

Boot modes

BOOT0
0
1
1
shows the external connection required to select the boot memory of the
Doc ID 18267 Rev 2
1.
Boot mode
Main Flash memory
System memory
Embedded SRAM
th
rising edge of SYSCLK after a reset. It
Ω
Ω
Aliasing
Main Flash memory is selected as boot
space
System memory is selected as boot
space
Embedded SRAM is selected as boot
space
AN3320