MS51
Nov. 28, 2019
Page
70
of 491
Rev 1.00
MS51
32K
SE
RIES
TE
CHNICAL RE
F
EREN
CE MA
N
UAL
CKEN
– Clock Enable
Register
SFR Address
Reset Value
CKEN
97H, PAGE 0, TA protected
0011_0000 b
7
6
5
4
3
2
1
0
EXTEN[1:0]
HIRCEN
-
-
-
-
CKSWTF
R/W
R/W
-
-
-
-
R
Bit
Name
Description
7:6
EXTEN[1:0]
External clock source enable
11 = External clock input via OSCIN (P30) Enabled
10 = External clock input via HXTIN (P00) Enabled
01 = External crystal 4~24 MHz Enabled
00 = external clock input is disable. P30/P00/P01 work as general purpose I/O or other
functions.
5
HIRCEN
High-speed internal oscillator 16 MHz enable
0 = The high-speed internal oscillator Disabled.
1 = The high-speed internal oscillator Enabled.
Note that once IAP is enabled by setting IAPEN (CHPCON.0), the high-speed internal 16 MHz
oscillator will be enabled automatically. The hardware will also set HIRCEN and HIRCST bits.
After IAPEN is cleared, HIRCEN and EHRCST resume the original values.
4:1
-
Reserved
0
CKSWTF
Clock switch fault flag
0 = The previous system clock source switch was successful.
1 = User tried to switch to an instable or disabled clock source at the previous system clock
source switch. If switching to an instable clock source, this bit remains 1 until the clock
source is stable and switching is successful.