GD32F10x User Manual
113
select by ENET_PHY_SEL bit in AFIO_PCF0 register.
The RTC is clocked by LXTAL clock or IRC40K clock or HXTAL clock divided by 128 (defined
which select by RTCSRC bit in backup domain control register (RCU_BDCTL). After the RTC
select HXTAL clock divided by 128, the clock disappeared when the 1.2V core domain power
off. After the RTC select IRC40K, the clock disappeared when V
DD
power off
.
After the RTC
select LXTAL, the clock disappeared when V
DD
and V
BAT
power off
.
The FWDGT is clocked by IRC40K clock, which is forced on when FWDGT started.
The FMC is clocked by IRC8M clock, which is forced on when IRC8M started.
5.5.2.
Characteristics
3 to 25 MHz High Speed crystal oscillator (HXTAL) .
Internal 8 MHz RC oscillator (IRC8M).
32,768 Hz Low Speed crystal oscillator (LXTAL).
Internal 40KHz RC oscillator (IRC40K).
PLL clock source can be HXTAL or IRC8M.
HXTAL clock monitor.
5.5.3.
Function overview
High speed crystal oscillator (HXTAL)
The high speed external crystal oscillator (HXTAL), which has a frequency from 3 to 25 MHz,
produces a highly accurate clock source for use as the system clock. A crystal with a specific
frequency must be connected and located close to the two HXTAL pins. The external resistor
and capacitor components connected to the crystal are necessary for proper oscillation.
Figure 5-7. HXTAL clock source
OSCIN
OSCOUT
C1
C2
Cryst al
The HXTAL crystal oscillator can be switched on or off using the HXTALEN bit in the control
register RCU_CTL. The HXTALSTB flag in control register RCU_CTL indicates if the high-
speed external crystal oscillator is stable. When the HXTAL is powered up, it will not be
released for use until this HXTALSTB bit is set by the hardware. This specific delay period is
known as the oscillator “Start-up time”. As the HXTAL becomes stable, an interrupt will be
Содержание GD32F10 Series
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