Hse Clock; Figure 13. Hse/ Lse Clock Sources - ST STM32F410 Reference Manual

Reset and clock control (RCC)
5.2.1

HSE clock

The high speed external clock signal (HSE) can be generated from two possible clock
sources:
•
HSE external crystal/ceramic resonator
•
HSE external user clock
The resonator and the load capacitors have to be placed as close as possible to the
oscillator pins in order to minimize output distortion and startup stabilization time. The
loading capacitance values must be adjusted according to the selected oscillator.
External clock
Crystal/ceramic
resonators
External source (HSE bypass)
In this mode, an external clock source must be provided. You select this mode by setting the
HSEBYP and HSEON bits in the
signal (square, sinus or triangle) with ~50% duty cycle has to drive the OSC_IN pin while the
OSC_OUT pin should be left HI-Z. See
External crystal/ceramic resonator (HSE crystal)
The HSE has the advantage of producing a very accurate rate on the main clock.
The associated hardware configuration is shown in
characteristics section of the datasheet for more details.
The HSERDY flag in the
external oscillator is stable or not. At startup, the clock is not released until this bit is set by
hardware. An interrupt can be generated if enabled in the
(RCC_CIR).
The HSE Crystal can be switched on and off using the HSEON bit in the
register (RCC_CR).
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Figure 13. HSE/ LSE clock sources

Hardware configuration
External
source
C
L1
RCC clock control register
Figure
RCC clock control register (RCC_CR)
RM0401 Rev 3
OSC_OUT
(HI-Z)
OSC_IN OSC_OUT
C
Load
capacitors
(RCC_CR). The external clock
13.
Figure 13. Refer to the electrical
indicates if the high-speed
RCC clock interrupt register
RM0401
L2
RCC clock control