
RM0008
Connectivity line devices: reset and clock control (RCC)
Doc ID 13902 Rev 12
123/1096
Figure 11.
Clock tree
1.
When the HSI is used as a PLL clock input, the maximum system clock frequency that can be achieved is
36 MHz.
2.
For full details about the internal and external clock source characteristics, please refer to the “Electrical
characteristics” section in your device datasheet.
The advanced clock controller features 3 PLLs to provide a high degree of flexibility to the
application in the choice of the external crystal or oscillator to run the core and peripherals
at the highest frequency and guarantee the appropriate frequency for the Ethernet and USB
OTG FS.
A single 25 MHz crystal can clock the entire system and all peripherals including the
Ethernet and USB OTG FS peripherals. In order to achieve high-quality audio performance,
an audio crystal can be used. In this case, the I2S master clock can generate all standard
sampling frequencies from 8 kHz to 96 kHz with less than 0.5% accuracy.
For more details about clock configuration for applications requiring Ethernet, USB OTG FS
and/or I
2
S (audio), please refer to "Appendix A Applicative block diagrams" in your
connectivity line device datasheet.
PLLMUL
PLL2MUL
PLL
3
MUL
PLLCLK
PLL2CLK
PLL
3
CLK to MCO
PREDIV1
S
CR
PREDIV2
x4, x5,... x9,
x6.5
x
8
, x9,... x14,
x16, x20
x
8
, x9,... x14,
x16, x20
/1,2,
3
....
..../15, /16
/1,2,
3
....
..../15, /16
H
S
E
O
S
C
8
MHz
H
S
I RC
/2
H
S
I
H
S
E
S
W
S
Y
S
CLK
/12
8
PREDIV1
PLL
S
CR
C
SS
L
S
E
O
S
C
L
S
I
RC
/2,
3
U
S
B pre
s
c
a
ler
RTC
S
EL[1:0]
L
S
E
L
S
I
IWDGCLK
to independent w
a
tchdog
to RTC
RTCCLK
OTGF
S
CLK
4
8
MHz
to U
S
B OTG F
S
3
-25 MHz
3
2.76
8
kHz
40 kHz
to I2
S3
interf
a
ce
to I2
S
2 interf
a
ce
to MCO
O
S
C
3
2_IN
O
S
C
3
2_OUT
O
S
C_IN
O
S
C_OUT
XT1 to MCO
AHB pre
s
c
a
ler
/1,/2 ../512
APB1 pre
s
c
a
ler
/1, 2, 4,
8
, 16
APB2 pre
s
c
a
ler
/1, 2, 4,
8
, 16
TIM2,
3
,4,5,6,7
If(APB1 pre
s
c
a
ler =1) x1
el
s
e x2
TIM1
If(APB2 pre
s
c
a
ler =1) x1
el
s
e x2
ADC pre
s
c
a
ler
/2, 4, 6,
8
TIMxCLK
to TIM2,
3
,4,5,
6 & 7
Peripher
a
l clock en
ab
le
3
6 MHz m
a
x
PCLK1
to APB1 peripher
a
l
s
Peripher
a
l clock en
ab
le
72 MHz m
a
x
PCLK2
to APB2 peripher
a
l
s
TIMxCLK
to TIM1
Peripher
a
l clock en
ab
le
Peripher
a
l clock en
ab
le
HCLK to AHB
bus
, core memory
a
nd DMA
/
8
to Cortex
S
y
s
tem timer
FCLK Cortex free r
u
nning clock
ADCCLK
to ADC1,2
S
Y
S
CLK
72 MHz m
a
x.
H
S
E
H
S
I
PLLCLK/2
PLL2CLK
PLL
3
CLK/2
PLL
3
CLK
XT1
MCO[
3
:0]
MCO
Ethernet
PHY
ETH_MII_TX_CLK
ETH_MII_RX_CLK
/2, /20
to Ethernet MAC
MACTXCLK
MACRXCLK
MACRMIICLK
(
s
ee note1)
s
y
s
tem clock
to Fl
as
h prog. IF
FLITFCLK
PLLVCO (2 × PLLCLK)
MII_RMII_
S
EL
in AFIO_MAPR
a
i15699d
14 MHz m
a
x
PLL
3
VCO
(2 × PLL
3
CLK)