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Clock management unit (CMU)
The clock sources of the whole system are: HSECLK, LSECLK, HSICLK,
LSICLK, PLL1 and PLL2. For the characteristics of the clock source, please
refer to the relevant chapter of "Electrical Characteristics" in the data manual.
External clock source
The external clock signal includes HSECLK (high-speed external clock signal)
and LSECLK (low-speed external clock signal).
There are two kinds of external clock sources:
External crystal/ceramic resonator
External clock of user
The hardware configuration of the two kinds of clock sources is shown in the
figure below.
Figure 5 HSECLK/LSECLK Clock Source Hardware Configuration
OSC_OUT
(Hi-Z)
External clock source
Crystal/ceramic
resonator
OSC_OUT
OSC_IN
C
L1
C
L2
External clock
Clock source
Hardware configuration
OSC_IN
In order to reduce the distortion of clock output and shorten the start-up
stabilization time, the crystal/ceramic resonator and load capacitor must be as
close to the oscillator pin as possible. The value of load capacitance (C
L1
, C
L2
)
must be adjusted according to the selected oscillator.
HSECLK high-speed external clock signal
HSECLK clock signal is generated by HSECLK external crystal/ceramic
resonator and HSECLK external clock two kinds of clock sources.
