Flash Memory Overview; Boot Configuration; Table 5. Boot Modes - ST STM32G4 Series Reference Manual

RM0440
2.5

Flash memory overview

The Flash memory is composed of two distinct physical areas:
•
The main Flash memory block. It contains the application program and user data if
necessary.
•
The information block. It is composed of three parts:
–
–
–
The Flash interface implements instruction access and data access based on the AHB
protocol. It also implements the logic necessary to carry out the Flash memory operations
(program/erase) controlled through the Flash registers. Refer to
memory (FLASH) for category 3 devices
for category 2 devices
2.6

Boot configuration

2.6.1 Boot configuration
Three different boot modes can be selected through the BOOT0 pin or the nBOOT0 bit into
the FLASH_OPTR register (if the nSWBOOT0 bit is cleared into the FLASH_OPTR
register), and nBOOT1 bit in FLASH_OPTR register, as shown in the following table.
BOOT_ nBOOT1
LOCK FLASH_OPTR[23]
1 X
0 X
0 X
0 0
0 0
0 1
0 1
The values on both BOOT0 pin (coming from the pin or the option bit) and nBOOT1 bit are
latched on the 4th edge of the internal startup clock source after reset release. It is up to the
user to set nBOOT1 and BOOT0 to select the required boot mode.
The BOOT0 pin or user option bit (depending on the nSWBOOT0 bit value in the
FLASH_OPTR register), and nBOOT1 bit are also re-sampled when exiting from Standby
Option bytes for hardware and memory protection user configuration.
System memory that contains the ST proprietary code.
OTP (one-time programmable) area
for more details.

Table 5. Boot modes

nBOOT0
FLASH_OPTR[27]
X
X
1
X
0
X
0
and Section 4: Embedded Flash memory (FLASH)
BOOT0 nSWBOOT0
pin PB8 FLASH_OPTR[26]
X
0
X
1
X
1
X
RM0440 Rev 1
Section 3: Embedded Flash
Boot Memory Space
Alias
X Main Flash memory
Main Flash memory is
1
selected as boot area
Main Flash memory is
0
selected as boot area
Embedded SRAM1 is
1
selected as boot area
Embedded SRAM1 is
0
selected as boot area
System memory is
1
selected as boot area
System memory is
0
selected as boot area
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