Datasheet

DocID15056 Rev 5 11/80
STM32F102x8, STM32F102xB Description
79
Figure 2. Clock tree
1. For the USB function to be available, both HSE and PLL must be enabled, with the USB clock output
(USBCLK) at 48 MHz.
2. To have an ADC conversion time of 1.2 µs, APB2 must be at 12 MHz, 24 MHz or 48 MHz.
3. The Flash memory programming interface clock (FLITFCLK) is always the HSI clock.
HSE OSC
4-16 MHz
OSC_IN
OSC_OUT
OSC32_IN
OSC32_OUT
LSE OSC
32.768 kHz
LSI RC
40 kHz
HS
I R
C
8 MHz
to Independent Watchdog (IWDG)
PLL
x2, x3, x4
PLLMUL
Legend:
MCO
Clock Output
Main
PLLXTPRE
/2
..., x16
AHB
Prescaler
/1, 2..512
/2
PLLCLK
HSI
HSE
APB1
Prescaler
/1, 2, 4, 8, 16
ADC
Prescaler
/2, 4, 6, 8
ADCCLK
PCLK1
HCLK
PLLCLK
to AHB bus, core,
memory and DMA
USBCLK
to USB interface
to TIM2, 3
and 4
USB
Prescaler
/1, 1.5
to ADC
LSE
LSI
HSI
/128
/2
HSI
HSE
peripherals
to APB1
Peripheral Clock
Enable (13 bits)
Enable (3 bits)
P
eripheral Clock
APB2
Prescaler
/1, 2, 4, 8, 16
PCLK2
peripherals
to APB2
Peripheral Clock
Enable (11 bits)
48 MHz
48 MHz max
48 MHz
48 MHz max
24 MHz max
to RTC
PLLSRC
SW
MCO
CSS
to Cortex System timer
/8
Clock
Enable (3 bits)
SYSCLK
max
RTCCLK
RTCSEL[1:0]
TIMXCLK
IWDGCLK
SYSCLK
FCLK Cortex
free running clock
TIM2,3, 4
If (APB1 prescaler =1) x1
else x2
HSE = high-speed external clock signal
HSI = high-speed internal clock signal
LSI = low-speed internal clock signal
LSE = low-speed external clock signal
ai14994b
To Flash prog. if FLITFCLK