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<strong>STM32W108C8</strong><br />
System modules<br />
Figure 5 shows a block diagram of the clocks in the <strong>STM32W108C8</strong>. This simplified view<br />
shows all the clock sources and the general areas of the chip to which they are routed.<br />
Figure 5.<br />
Clocks block diagram<br />
OSC24M_CTRL[0]<br />
12MHz<br />
RC<br />
Failover monitor<br />
(selects RC when<br />
XTAL fails )<br />
24MHz<br />
XTAL<br />
oscillator<br />
OSC24M_CTRL[1]<br />
OSCHF<br />
OSC 24M<br />
SCLK<br />
/2<br />
PCLK<br />
ADC<br />
SigmaDelta<br />
Produces 6MHz<br />
or 1MHz<br />
10kHz<br />
RC<br />
OSCRC<br />
/N<br />
(nominal 10)<br />
CLK1K<br />
ADC_CFG[2]<br />
CPU_CLKSEL[0]<br />
32kHz<br />
XTAL<br />
oscillator<br />
OSC32K<br />
FLITF<br />
bus<br />
Flash<br />
32kHz<br />
digital in<br />
SLEEPTMR _CLKEN[0]<br />
bus<br />
FCLK<br />
CPU<br />
bus<br />
RAM CTRL<br />
bus<br />
RAM<br />
Watchdog<br />
counter<br />
SysTick<br />
counter<br />
Sleep Timer<br />
counter<br />
/(2^N)<br />
ST _CSR[2]<br />
SLEEPTMR _CFG[7:4]<br />
SLEEPTMR _CFG[0]<br />
MAC Timer<br />
counter<br />
TIMx<br />
counter<br />
TIMx_SMCR[2:0]<br />
TIMxCLK<br />
digital in<br />
SCx<br />
RATEGEN<br />
SCxSCLK<br />
digital i /o<br />
TIMx_OR[1:0]<br />
DEBUG_EMCR[24]<br />
AND<br />
/2<br />
TRACECLK<br />
digital out<br />
6.3.1 High-frequency internal RC oscillator (OSCHF)<br />
The high-frequency RC oscillator (OSCHF) is used as the default system clock source when<br />
power is applied to the core domain. The nominal frequency coming out of reset is 12 MHz.<br />
Most peripherals, excluding the radio peripheral, are fully functional using the OSCHF clock<br />
source. Application software must be aware that peripherals are clocked at different speeds<br />
depending on whether OSCHF or OSC24M is being used. Since the frequency step of<br />
OSCHF is 0.5 MHz and the high-frequency crystal oscillator is used for calibration, the<br />
Doc ID 018587 Rev 2 38/215
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