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GD32F10x User Manual
114
generated if the related interrupt enable bit HXTALSTBIE in the Interrupt register RCU_INT
is set. At this point the HXTAL clock can be used directly as the system clock source or the
PLL input clock.
Select external clock bypass mode by setting the HXTALBPS and HXTALEN bits in the
control register RCU_CTL. During bypass mode, the signal is connected to OSCIN, and
OSCOUT remains in the suspended state, as shown in
Figure 5-8. HXTAL clock source in
.The CK_HXTAL is equal to the external clock which drives the OSCIN pin.
Figure 5-8. HXTAL clock source in bypass mode
OSCIN
OSCOUT
Exte rnal cl ock
Internal 8M RC oscillators (IRC8M)
The internal 8M RC oscillator, IRC8M, has a fixed frequency of 8 MHz and is the default clock
source selection for the CPU when the device is powered up. The IRC8M oscillator provides
a lower cost type clock source as no external components are required. The IRC8M RC
oscillator can be switched on or off using the IRC8MEN bit in the control register RCU_CTL.
The IRC8MSTB flag in the control register RCU_CTL is used to indicate if the internal 8M RC
oscillator is stable. The start-up time of the IRC8M oscillator is shorter than the HXTAL crystal
oscillator. An interrupt can be generated if the related interrupt enable bit, IRC8MSTBIE, in
the clock interrupt register, RCU_INT, is set when the IRC8M becomes stable. The IRC8M
clock can also be used as the system clock source or the PLL input clock.
The frequency accuracy of the IRC8M can be calibrated by the manufacturer, but its operating
frequency is still less accurate than HXTAL. The application requirements, environment and
cost will determine which oscillator type is selected.
If the HXTAL or PLL is the system clock source, to minimize the time required for the system
to recover from the Deep-sleep Mode, the hardware forces the IRC8M clock to be the system
clock when the system initially wakes-up.
Phase locked loop (PLL)
There are three internal Phase Locked Loop, including PLL, PLL1 and PLL2.
The PLL can be switched on or off by using the PLLEN bit in the RCU_CTL register. The
PLLSTB flag in the RCU_CTL register will indicate if the PLL clock is stable. An interrupt can
be generated if the related interrupt enable bit, PLLSTBIE, in the RCU_INT Register, is set
as the PLL becomes stable.
Содержание GD32F10 Series
Страница 1: ...GigaDevice Semiconductor Inc GD32F10x Arm Cortex M3 32 bit MCU User Manual Revision 2 6 Jun 2022 ...
Страница 63: ...GD32F10x User Manual 63 programmed during the chip production ...
Страница 117: ...GD32F10x User Manual 117 010 1 0 011 0 9 ...
Страница 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
Страница 427: ...GD32F10x User Manual 427 value ...
Страница 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...