
Rev. 1.00
109 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
6 Clock Control Unit (CKCU)
6 Clock Control Unit (CKCU)
Bits
Field
Descriptions
[1:0]
AFIOPCLK
AFIO Peripheral Clock Selection
00: PCLK = CK_AHB
01: PCLK = CK_AHB / 2
10: PCLK = CK_AHB / 4
11: PCLK = CK_AHB / 8
PCLK = Peripheral Clock; CK_AHB = AHB and CPU clock
HSI Control Register – HSICR
This register is used to control the frequency trimming of the HSI RC oscillation.
Offset:
0x040
Reset value:
0xXXXX_0000 where X is undefined
31
30
29
28
27
26
25
24
Reserved
HSICOARSE
Type/Reset
RO X RO X RO X RO X RO X
23
22
21
20
19
18
17
16
HSIFINE
Type/Reset RW X RW X RW X RW X RW X
RW X
RW X
RW X
15
14
13
12
11
10
9
8
Reserved
Type/Reset
7
6
5
4
3
2
1
0
FLOCK
REFCLKSEL
TMSEL
ATMSEL
LTRSEL
ATCEN
TRIMEN
Type/Reset RO 0 RW 0 RW 0 RW 0 RW 0 RW 0 RW 0 RW 0
Bits
Field
Descriptions
[28:24]
HSICOARSE
HSI Clock Coarse Trimming Value
These bits are initialized automatically at startup. They are adjusted by factory
trimming and cannot be trimmed by program.
[23:16]
HSIFINE
HSI Clock Fine Trimming Value
These bits are initialized automatically at startup. They are also adjusted by
factory trimming. But these bits provide an additional user-programmable
trimming value that is added to the HSICOARSE[4:0] bits to get more accurate
or compensate the variations in voltage and temperature that influence the HSI
frequency. It can be programmed by software or automatically adjusted by the
Auto Trimming Controller (ATC) together with an external reference clock.
[7]
FLOCK
Frequency Lock
0: HSI frequency is not trimmed into target range
1: HSI frequency is trimmed into target range
[6:5]
REFCLKSEL
Reference Clock Selection
00: Select 32.768 kHz external low speed clock source (LSE)
01: Reserved
1x: Select external pin (CKIN) 1 kHz pulse
These bits are used to select the reference clock for the HSI Auto Trimming
Controller.