CMS32L051 User Manual |Chapter 4 Clock Generation Circuit
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4.4.3 High-speed internal oscillator
The CMS32L051 has a built-in high-speed internal oscillator. The frequency can be selected from 64MHz,
48MHz, 32MHz, 24MHz, 16MHz, 12MHz, 8MHz, 6MHz, 4MHz, 3MHz and 2MHz via the option byte (000C2H).
The oscillation can be controlled via bit 0 (HIOSTOP) of the Clock Operation Status Control Register (CSC).
After the power-on reset is released, the high-speed internal oscillator automatically begins to oscillate.
4.4.4 Low-speed internal oscillator
The CMS32L051 has a built-in low-speed internal oscillator.
The low-speed internal oscillator clock is used as the watchdog timer, real-time clock, 15-bit interval timer,
and the external reference clock for the SysTick timer, as well as a CPU clock and a peripheral module clock.
When option byte (000C0H) bit4 (WDTON) or the subsystem clock provides a mode control register
(OSMC) of bit4(). WUTMMCK0) is 1, the low-speed internal oscillator oscillates.
When the watchdog timer stops running and the WUTMMCK0 bit is not 0, the low-speed internal oscillator
continues to oscillate. However, if the watchdog timer is running and the WUTMMCK0 bit is 0, the low-speed
internal oscillator stops oscillating when the WDSTBYON bit is 0 and in sleep mode, deep sleep mode. When
the watchdog timer is running, the low-speed internal oscillator clock does not stop running, even if the program
is out of control.
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