STM8S003F3 STM8S003K3
Product overview
4.5
Clock controller
The clock controller distributes the system clock (f
coming from different oscillators
MASTER)
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. The clock signal is not switched until the new clock
source is ready. The design guarantees glitch-free switching.
•
•
Clock management: To reduce power consumption, the clock controller can stop the
clock to the core, individual peripherals or memory.
Master clock sources: Four different clock sources can be used to drive the master
clock:
–
–
–
–
1-16 MHz high-speed external crystal (HSE)
Up to 16 MHz high-speed user-external clock (HSE user-ext)
16 MHz high-speed internal RC oscillator (HSI)
128 kHz low-speed internal RC (LSI)
•
•
•
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 an HSE
clock failure occurs, the internal RC (16 MHz/8) is automatically selected by the CSS
and an interrupt can optionally be generated.
Configurable main clock output (CCO): This outputs an external clock for use by the
application.
Table 2. Peripheral clock gating bit assignments in CLK_PCKENR1/2 registers
Peripheral
clock
Peripheral
clock
Peripheral
clock
Peripheral
clock
Bit
Bit
Bit
Bit
PCKEN17
PCKEN16
PCKEN15
PCKEN14
TIM1
TIM3
TIM2
TIM4
PCKEN13
UART1
PCKEN27 Reserved PCKEN23
ADC
AWU
PCKEN12 Reserved PCKEN26 Reserved PCKEN22
PCKEN11
PCKEN10
SPI
I2C
PCKEN25 Reserved PCKEN21 Reserved
PCKEN24 Reserved PCKEN20 Reserved
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