GD32W51x User Manual
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The frequency of AHB, APB2 and the APB1 domains can be configured by each prescaler.
The maximum frequency of the AHB and the APB2/APB1 domains is 180MHz/90MHz/45
MHz. The Cortex-M33 System Timer (SysTick) external clock is clocked with the AHB clock
(HCLK) divided by 8. The SysTick can work either with this clock or with the AHB clock
(HCLK), configurable in the SysTick Control and Status Register.
The ADCs are clocked by the clock of APB2 divided by 2, 4, 6, 8 or by the clock of AHB
divided by 5, 6, 10, 20, which defined by ADCCK in ADC_CCTL register.
The TIMERs are clocked by the clock divided from CK_AHB. The frequency of TIMERs clock
is equal to CK_APBx, twice the CK_APBx or four times the CK_APBx. Please refer to
TIMERSEL bit in RCU_CFG1 for detail.
The USBFS /TRNG/ clocks are selected from the clock of PLL or PLLDIG.
The SDIO is clocked by PLL or PLLDIG or
IRC16M clock or HXTAL clock, which selected by
SDIOSEL bits in RCU_ADDCTL register.
The I2S is clocked by the clock of PLLI2SR or External PIN I2S_CKIN which defined by
I2SSEL bit in RCU_ADDCTL register.
The RTC is clocked by LXTAL clock or IRC32K clock or HXTAL clock divided by 2 to 32
(defined by RTCDIV bits in RCU_CFG0) which select by RTCSRC bit in Backup Domain
Control Register (RCU_BDCTL). After the RTC select HXTAL clock divided by 2 to 31
(defined by RTCDIV bits in RCU_CFG0), the clock disappeared when the 1.2V core domain
power off. After the RTC select IRC32K, the clock disappeared when V
DD
power off
.
When the
RTC select LXTAL, the clock disappeared when V
DD
and V
BAT
power off
.
The FWDGT is clocked by IRC32K clock, which is forced on when FWDGT started.
The USART0/2 is clocked by IRC16M clock or LXTAL clock or
System clock or APB2 clock,
which selected by USART0SEL bits in RCU_CFG1 register.
The I2C0 is clocked by IRC16M clock or
System clock or APB1 clock, which selected by
I2C0SEL bits in RCU_CFG1 register.
The HPDF is clocked by PCLK2 clock or System clock, which selected by HPDFSEL bit in
RCU_ADDCTL register.
The HPDF_AUDIO is clocked by PLLI2S or External I2S_CKIN PIN or PLL or IRC16M which
defined by HPDFADUIOSEL bit in RCU_ADDCTL register.
6.2.2.
Characteristics
20 to 52 MHz High Speed crystal oscillator (HXTAL)
Internal 16 MHz RC oscillator (IRC16M)
32,768 Hz Low Speed crystal oscillator (LXTAL)
Internal 32KHz RC oscillator (IRC32K)
PLL clock source can be HXTAL or IRC16M