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NUC126
Aug. 08, 2018
Page
177
of 943
Rev 1.03
NUC12
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6.3.7
Register Description
System Power-down Control Register (CLK_PWRCTL)
Register
Offset
R/W
Description
Reset Value
CLK_PWRCT
L
0x00
R/W
System Power-down Control Register
0x0000_1C1X
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
Reserved
HIRC48EN
HXTSELTYP
HXTGAIN
Reserved
7
6
5
4
3
2
1
0
PDEN
PDWKIF
PDWKIEN
PDWKDLY
LIRCEN
HIRCEN
LXTEN
HXTEN
Bits
Description
[31:14]
Reserved
Reserved.
[13]
HIRC48EN
HIRC48 Enable Bit (Write Protect)
0 = 48 MHz internal high speed RC oscillator (HIRC48) Disabled.
1 = 48 MHz internal high speed RC oscillator (HIRC48) Enabled.
Note:
This bit is write protected. Refer to the SYS_REGLCTL register.
[12]
HXTSELTYP
HXT Crystal Type Select Bit (Write Protect)
This is a protected register. Please refer to open lock sequence to program it.
0 = Select INV type.
1 = Select GM type.
Note:
This bit is write protected. Refer to the SYS_REGLCTL register.
[11:10]
HXTGAIN
HXT Gain Control Bit (Write Protect)
Gain control is used to enlarge the gain of crystal to make sure crystal work normally. If
gain control is enabled, crystal will consume more power than gain control off.
00 = HXT frequency is lower than from 8 MHz.
01 = HXT frequency is from 8 MHz to 12 MHz.
10 = HXT frequency is from 12 MHz to 16 MHz.
11 = HXT frequency is higher than 16 MHz.
Note:
This bit is write protected. Refer to the SYS_REGLCTL register.
[9:8]
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 till 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, HIRC and the HIRC48 will be disabled in this mode, but LXT
and LIRC are not controlled by Power-down mode.