Memory map and Image structure

Runtime memory map

0x20300100 0x20100000	Registers
0x1000000 0x800000	FLASH 8M Max
0x130000 0x128000 0x100000	EM(BLE) 32K
	SRAM 160K
0x20000 0x0	ROM 128K

注解

The address ranged from 0x800000 to 0x1000000 is memory-mapped for QSPI-FLASH only when hardware cache is working. Hardware cache automatically manages QSPI Controller, fetches data from Flash, returns the data to system bus. If the program is going to perform the operation, such as erase, program, read, on Flash, hardware cache will be disabled until the operation is done.

Flash usage

Flash Offset	Memory Mapped Address
data_base	0x800000+data_base	bxfs data
ota_base	0x800000+ota_base	ota image
0x3000	0x803000	active image
0x2000	0x802000	information page
0x0	0x800000	bootloader

The bootloader is placed at the first 8KB of Flash.

The next 4KB is used for information page.

Information page

An area where product parameters are stored. This area are often programed to different values during production. The first 6 bytes of information page are predefined for BLE Public MAC Address.

The ota_base and data_base are designated in config.ini,see Flash parameters configuration for bootloader.

Ota_base

When performing firmware OTA, the new image is temporarily placed at ota_base. The new image will be copied to original image base 0x803000 after authentication in the boot sequence.

Data_base

Persistent data are stored in flash starting from data_base by BXFS. Such as security data of bonding in BLE application, network status data in MESH application. See BXFS for how it manages persistent data.