Nuvoton NuMicro MS51PC0AE - Page 207

MS51
Nov. 28, 2019 Page 207 of 491 Rev 1.00
MS51 32K SERIES TECHNICAL REFERENCE MANUAL
CKSWT – Clock Switch
Register
SFR Address
Reset Value
CKSWT
96H, PAGE 0, TA protected
0011_0000 b
7
6
5
4
3
2
1
0
HXTST
ECKP00ST
HIRCST
LIRCST
ECKP30ST
OSC[1:0]
-
R
R
R
R
R
W
-
Bit
Name
Description
7
HXTST
High-speed external crystal 4 MHz to 24 MHz status
0 = High-speed external crystal is not stable or disabled.
1 = High-speed external crystal is enabled and stable.
6
ECKP00ST
External clock P00 input status
0 = External clock P00 input is not stable or disabled.
1 = External clock P00 input is enabled and stable.
5
HIRCST
High-speed internal oscillator 16 MHz status
0 = High-speed internal oscillator is not stable or disabled.
1 = High-speed internal oscillator is enabled and stable.
-
-
Reserved
3
ECKP30ST
External clock P30 input status
0 = External clock P30 input is not stable or disabled.
1 = External clock P30 input is enabled and stable.
2:1
OSC[1:0]
Oscillator selection bits
This field selects the system clock source.
00 = Internal 16 MHz oscillator.
01 = External clock source according to EXTEN[1:0] (CKEN[7:6]) setting.
10 = Internal 10 kHz oscillator.
11 = Reserved.
Note that this field is write only. The read back value of this field may not correspond to the
present system clock source.