GD32F20x User Manual
82
Figure 5-2. Clock tree
/2
3-25 MHz
HXTAL
8 MHz
IRC8M
×2,3,4
…,32
PLL
Clock
Monitor
PLLSEL
PLLMF
0
1
00
01
10
CK_IRC8M
CK_HXTAL
CK_PLL
CK_SYS
120 MHz max
AHB
Prescaler
÷
1,2...512
CK_AHB
120 MHz max
APB1
Prescaler
÷
1,2,4,8,16
TIMER1,2,3,4,5,6,
11,12,13 if(APB1
prescale =1)x1
else x 2
APB2
Prescaler
÷
1,2,4,8,16
TIMER0,7,8,9,10
if(APB2 prescale
=1)x1
else x 2
ADC
Prescaler
÷
2,4,6,8,12,1
6
CK_APB2
120 MHz max
Peripheral enable
PCLK2
to APB2 peripherals
CK_APB1
60 MHz max
Peripheral enable
PCLK1
to APB1 peripherals
TIMERx
enable
CK_TIMERx
to TIMER0,7,8,9,10
TIMERx
enable
CK_TIMERx
to TIMER1,2,3,4,5,
6,11,12,13
CK_ADCX to ADC0,1,2
28 MHz max
AHB enable
HCLK
(to AHB bus,Cortex-M3,SRAM,DMA)
EXMC enable
CK_EXMC
(to EXMC)
÷8
CK_CST
(to Cortex-M3 SysTick)
FCLK
(free running clock)
USBFS
Prescaler
÷1,1.5,2,2.5
CK_USBFS(=48 MHz)
or CK_TRNG(<=48 MHz)
(to USBFS or TRNG )
32.768 KHz
LXTAL
11
10
01
40 KHz
IRC40K
CK_RTC
CK_FWDGT
(to RTC)
(to FWDGT)
/128
CK_OUT0
SCS[1:0]
RTCSRC[1:0]
PREDV0
0
1
CK_PLL
CK_HXTAL
CK_IRC8M
CK_SYS
/2
0111
00xx
NO CLK
0100
0101
0110
CKOUT0SEL[3:0]
EXT1
/2
1000
1001
1010
CK_PLL1
CK_PLL2
1011
CK_PLL2
/1,2,3
…
15,16
PREDV1
×8,9,10
…,
14,16,20
PLL1
PLL1MF
PLL2MF
×8,9,10
…,
14,16,20
PLL2
CK_PLL1
CK_PLL2
/1,2,3
…
15,16
x2
I2S1/2SEL
0
1
CK_I2S
(to I2S1,2)
1
/2,20
0
1
CK_MACTX
0
1
CK_MACRX
CK_FMC
(to FMC)
Ethernet
PHY
EXT1 to
CK_OUT
CK_MACRMII
PREDV0SEL
CKOUT0DIV
÷
1,2...64
CK_OUT1
CK_PLL
CK_HXTAL
CK_IRC8M
CK_SYS
/2
0111
00xx
NO CLK
0100
0101
0110
CKOUT1SEL[3:0]
EXT1
/2
1000
1001
1010
CK_PLL1
CK_PLL2
1011
CK_PLL2
CKOUT1DIV
÷
1,2...64
CK_DCI
(to DCI)
Peripheral enable
CK_CAU
(to CAU )
Peripheral enable
CK_HAU
(to HAU)
Peripheral enable
PLLTSEL
1
0
CK_HXTAL
PLLT prescaler
(
PLLTPSC
)
÷
2,3...63
PLLT input clock
VCO input clock ×49,50,
…,432
PLLTMF
CK_VCO
PLLTR prescaler
(
PLLTRPSC
)
÷
2,3...7
CK_PLLTR
TLI prescaler
(TLIPSC )
÷2,4,8,16
CK_TLI
CK_IRC8M
CK_SDIO
(to SDIO)
Peripheral enable
The RCU controller of connectivity line devices has three PLLs(PLL, PLL1, PLL2) and can
provide a variety of configuration of clock frequency to meet the needs of microcontrollers.
The frequency of AHB, APB2 and the APB1 domains can be configured by each prescaler.
The maximum frequency of the AHB, APB2 and APB1 domains is 120 MHz/120 MHz/60 MHz.
The RCU is used as the external clock of Cortex system Timer(SysTick) after the AHB clock
(HCLK) divided by 8. The SysTick can work either with this clock or with the AHB clock (HCLK)
by configuring the SysTick Control and Status Register.
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...