M451
May. 4, 2018
Page
269
of
1006
Rev.2.08
M4
51
S
E
RI
E
S
T
E
CH
NICA
L RE
F
E
R
E
NC
E
M
A
NU
A
L
6.3.2 Clock Generator
The clock generator consists of 5 clock sources, which are listed below:
32.768 kHz external low speed crystal oscillator (LXT)
4~20 MHz external high speed crystal oscillator (HXT)
Programmable PLL output clock frequency (PLLFOUT), PLL source can be selected
from external 4~20 MHz external high speed crystal (HXT) or 22.1184 MHz internal
high speed oscillator (HIRC)
22.1184 MHz internal high speed RC oscillator (HIRC)
10 kHz internal low speed RC oscillator (LIRC)
XT1_OUT
External 4~24
MHz Crystal
(HXT)
HXTEN (CLK_PWRCTL[0])
XT1_IN
Internal
22.1184 MHz
Oscillator
(HIRC)
HIRCEN (CLK_PWRCTL[2])
0
1
PLL
PLLSRC (CLK_PLLCTL[19])
PLL FOUT
X32_OUT
External 32.768
kHz Crystal
(LXT)
LXT
LXTEN (CLK_PWRCTL[1])
X32_IN
Internal 10 kHz
Oscillator
(LIRC)
LIRCEN (CLK_PWRCTL[3])
HXT
HIRC
LIRC
Figure 6.3-2 Clock Generator Block Diagram
