Datasheet

Functional overview STM8L052C6
14/52 Doc ID 022924 Rev 2
3.4 Clock management
The clock controller distributes the system clock (SYSCLK) coming from different oscillators
to the core and the peripherals. It also manages clock gating for low power modes and
ensures clock robustness.
Features
● Clock prescaler: To get the best compromise between speed and current
consumption the clock frequency to the CPU and peripherals can be adjusted by a
programmable prescaler.
● Safe clock switching: Clock sources can be changed safely on the fly in run mode
through a configuration register.
● Clock management: To reduce power consumption, the clock controller can stop the
clock to the core, individual peripherals or memory.
● System clock sources: 4 different clock sources can be used to drive the system
clock:
– 1-16 MHz High speed external crystal (HSE)
– 16 MHz High speed internal RC oscillator (HSI)
– 32.768 kHz Low speed external crystal (LSE)
– 38 kHz Low speed internal RC (LSI)
● RTC and LCD clock sources: The above four sources can be chosen to clock the
RTC and the LCD, whatever the system clock.
● Startup clock: After reset, the microcontroller restarts by default with an internal
2 MHz clock (HSI/8). The prescaler ratio and clock source can be changed by the
application program as soon as the code execution starts.
● Clock security system (CSS): This feature can be enabled by software. If a HSE clock
failure occurs, the system clock is automatically switched to HSI.
● Configurable main clock output (CCO): This outputs an external clock for use by the
application.