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Rev. 1.00
50 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
4 Flash Memory Controller (FMC)
Option Byte Description
The Option Byte area can be treated as an independent Flash memory of which the base address is
0x1FF0_0000. The following table shows the functional description and the Option Byte memory
map.
Table 8. Option Byte Memory Map
Option Byte
Offset
Description
Reset Value
Option Byte Base Address = 0x1FF0_0000
OB_PP
0x000
0x004
0x008
0x00C
Flash Page Erase/Program Protection
OB_PP [n] (n = 0 ~ X)
0: Flash Page n Erase / Program Protection is enabled
1: Flash Page n Erase / Program Protection is disabled
OB_PP [n] (n = (X + 1) ~ 127)
Reserved
For the HT32F54231 the variable “X” is equal to 31.
For the HT32F54241 the variable “X” is equal to 62.
For the HT32F54243 the variable “X” is equal to 63.
For the HT32F54253 the variable “X” is equal to 126.
0xFFFF_FFFF
0xFFFF_FFFF
0xFFFF_FFFF
0xFFFF_FFFF
OB_CP
0x010
Flash Security Protection
OB_CP [0]
0: Flash Security protection is enabled
1: Flash Security protection is disabled
Option Byte Protection
OB_CP [1]
0: Option Byte protection is enabled
1: Option Byte protection is disabled
OB_CP [31:2]: Reserved
0xFFFF_FFFF
OB_CK
0x020
Flash Option Byte Checksum
OB_CK [31:0]
OB_CK should be set as the sum of 5 words of Option Byte
content, of which the offset address ranges from 0x000 to 0x010
(0x000 + 0x004 + 0x008 + 0x00C + 0x010), when the OB_PP or
OB_CP register content is not equal to 0xFFFF_FFFF. Otherwise,
both page erase/program protection and security protection will
be enabled.
0xFFFF_FFFF
OB_WDT
0x02C
Flash Option Watchdog Timer Enable
OB_WDT [15:0]: 0x7A92
If the OB_WDT [15:0] is set to 0x7A92, the WDT will be enabled
immediately when the MCU power on reset or system reset
occurs. The WDT can be disabled by software.
OB_WDT [31:16]: Reserved
0xFFFF_FFFF
OB_TOOL
0x030 ~ 0x04C Reserved for Flash writer tool and boot loader.
0xFFFF_FFFF