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M0A21/M0A23 Series
May 06, 2022
Page
189
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
6.3.8
Register Description
System Power-down Control Register (CLK_PWRCTL)
Register
Offset
R/W
Description
Reset Value
CLK_PWRCTL
0x00
R/W
System Power-down Control Register
0xB901_001X
31
30
29
28
27
26
25
24
HXTSELXT
HXTGAIN
LXTSELXT
LXTGAIN
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
Reserved
7
6
5
4
3
2
1
0
PDEN
PDWKIF
PDWKIEN
PDWKDLY
LIRCEN
HIRCEN
LXTEN
HXTEN
Bits
Description
[31]
HXTSELXT
HXT Crystal Mode Selection
0 = HXT works as external clock mode. PA.5 is configured as external clock input pin.
1 = HXT works as crystal mode. PA.4 and PA.5 are configured as high speed crystal (HXT) pins.
Note 1:
When HXTSELXT = 0, PA.4 MFP should be set as GPIO mode. The DC characteristic of XT1_OUT
is the same as GPIO.
Note 2:
This bit is write protected. Refer to the SYS_REGLCTL register.
[30:28]
HXTGAIN
HXT Gain Control Bit (Write Protect)
Please refer to HXT Charateristic.
Note:
This bit is write protected. Refer to the SYS_REGLCTL register.
[27]
LXTSELXT
LXT Crystal Mode Selection
0 = LXT works as external clock mode. PC.5 is configured as external clock input pin.
1 = LXT works as crystal mode. PC.4 and PC.5 are configured as low speed crystal (LXT) pins.
Note 1:
When LXTSELXT = 0, PC.4 MFP should be set as GPIO mode. The DC characteristic of X32_OUT
is the same as GPIO.
Note 2:
This bit is write protected. Refer to the SYS_REGLCTL register.
[26:24]
LXTGAIN
LXT Gain Control Bit (Write Protect)
Please refer to LXT Charateristic.
Note:
This bit is write protected. Refer to the SYS_REGLCTL register.
[23:8]
Reserved
Reserved.
[7]
PDEN
System Power-down Enable (Write Protect)
When this bit is set to 1, Power-down mode is enabled and chip keeps active utill the CPU sleep mode is
also active and then the chip enters Power-down mode.
When chip wakes up from Power-down mode, this bit is auto cleared. Users need to set this bit again for
next Power-down.
In Power-down mode, HXT and the HIRC will be disabled in this mode, but LXT and LIRC are not controlled
by Power-down mode. If user disable LIRC before entering power-down mode, this bit should be set after
LIRC disabled 50us.