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M0A21/M0A23 Series
May 06, 2022
Page
196
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
Clock Source Select Control Register 1 (CLK_CLKSEL1)
Before clock switching, the related clock sources (pre-selected and newly-selected) must be turned on.
Register
Offset
R/W
Description
Reset Value
CLK_CLKSEL1
0x14
R/W
Clock Source Select Control Register 1
0x4477_773B
31
30
29
28
27
26
25
24
Reserved
UART1SEL
Reserved
UART0SEL
23
22
21
20
19
18
17
16
Reserved
TMR3SEL
Reserved
TMR2SEL
15
14
13
12
11
10
9
8
Reserved
TMR1SEL
Reserved
TMR0SEL
7
6
5
4
3
2
1
0
Reserved
CLKOSEL
WWDTSEL
WDTSEL
Bits
Description
[31]
Reserved
Reserved.
[30:28]
UART1SEL
UART1 Clock Source Selection
000 = Clock source from external high speed crystal oscillator (HXT).
010 = Clock source from external low speed crystal oscillator (LXT).
011 = Clock source from internal high speed RC oscillator (HIRC).
100 = Clock source from PCLK1.
101 = Clock source from internal low speed RC oscillator (LIRC).
Other = Reserved.
[27]
Reserved
Reserved.
[26:24]
UART0SEL
UART0 Clock Source Selection
000 = Clock source from external high speed crystal oscillator (HXT).
010 = Clock source from external low speed crystal oscillator (LXT).
011 = Clock source from internal high speed RC oscillator (HIRC).
100 = Clock source from PCLK0.
101 = Clock source from internal low speed RC oscillator (LIRC).
Other = Reserved.
[23]
Reserved
Reserved.
[22:20]
TMR3SEL
TIMER3 Clock Source Selection
000 = Clock source from external high speed crystal oscillator (HXT).
001 = Clock source from external low speed crystal oscillator (LXT).
010 = Clock source from PCLK1.
011 = Clock source from external clock T3 pin.
101 = Clock source from internal low speed RC oscillator (LIRC).
111 = Clock source from internal high speed RC oscillator (HIRC).
Others = Reserved.