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Rev. 1.00
104 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
6 Clock Control Unit (CKCU)
Clock Source Status Register – CKST
This register specifies status of various clock sources.
Offset:
0x034
Reset value: 0x0100_0003
31
30
29
28
27
26
25
24
Reserved
HSIST
Type/Reset
RO 0 RO 0 RO 0 RO 1
23
22
21
20
19
18
17
16
Reserved
HSEST
Type/Reset
RO 0 RO 0 RO 0
15
14
13
12
11
10
9
8
Reserved
PLLST
Type/Reset
RO 0 RO 0 RO 0 RO 0
7
6
5
4
3
2
1
0
Reserved
CKSWST
Type/Reset
RO 0 RO 1 RO 1
Bits
Field
Descriptions
[27:24]
HSIST
Internal High Speed Clock Occupation Status (CK_HSI)
xxx1: HSI is used by System Clock (CK_SYS) (SW = 0x3)
xx1x: HSI is used by System PLL
x1xx: HSI is used by Clock Monitor
[18:16]
HSEST
External High Speed Clock Occupation Status (CK_HSE)
xx1: HSE is used by System Clock (CK_SYS) (SW = 0x2)
x1x: HSE is used by System PLL
[11:8]
PLLST
PLL Clock Occupation Status
xxx1: PLL is used by System Clock (CK_SYS)
xx1x: PLL is used by USART
1xxx: PLL is used by CK_REF
[2:0]
CKSWST
Clock Switch Status
00x: CK_PLL clock out as system clock
010: CK_HSE as system clock
011: CK_HSI as system clock
110: CK_LSE as system clock
111: CK_LSI as system clock
The fields are status to indicate which clock source is being used as system clock
currently.