AT32F421 Series Reference Manual
2022.11.11 Page 81 Rev 2.02
5.8.18 Flash extension memory security library setting register
(EM_SLIB_SET)
For Flash extension area only.
Kept at its default value
Extension memory sLib instruction start sector
00000000: Sector 0
00000001: Sector 1
00000010: Sector 2
00000011: Sector 3
11111111: No sLib instruction area
Others: Invalid
Note: When this bit is set to 0xFF, it indicates that the
Flash memory extension area from sector 0 to sector 3 is
defined as the security library, and the entire security
library is read-only.
Extension memory sLib setting
By writing 0x5AA5, the extension memory is configured
as an area to store security library code.
Note: All these bits are write-only, and return no response when being read.
5.8.19 Boot memory mode setting register (BTM_MODE_SET)
For boot memory only.
Kept at its default value.
Boot memory mode setting
0XFF: Boot memory serves as a system area that stores
system boot code
Others: Boot memory serves a Flash extension area that
stores application code
Note: This register can be set only when Flash access
protection is disabled.
Note: All these bits are write-only, and return no response when being read.
5.8.20 Security library unlock register (FLASH_UNLOCK)
For security library register unlock only.
Security library unlock key value
The fixed key value is 0xA35F_6D24, which is used for
the unlocking of security library setting register.
Note: All these bits are write-only, and return 0 when being read.
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