ST STM32F410 Reference Manual page 103

RM0401
Bit 16 HSEON: HSE clock enable
Bits 15:8 HSICAL[7:0]: Internal high-speed clock calibration
Bits 7:3 HSITRIM[4:0]: Internal high-speed clock trimming
Bit 2 Reserved, must be kept at reset value.
Bit 1 HSIRDY: Internal high-speed clock ready flag
Bit 0 HSION: Internal high-speed clock enable
Set and cleared by software.
Cleared by hardware to stop the HSE oscillator when entering Stop or Standby mode. This
bit cannot be reset if the HSE oscillator is used directly or indirectly as the system clock.
0: HSE oscillator OFF
1: HSE oscillator ON
These bits are initialized automatically at startup.
These bits provide an additional user-programmable trimming value that is added to the
HSICAL[7:0] bits. It can be programmed to adjust to variations in voltage and temperature
that influence the frequency of the internal HSI RC.
Set by hardware to indicate that the HSI oscillator is stable. After the HSION bit is cleared,
HSIRDY goes low after 6 HSI clock cycles.
0: HSI oscillator not ready
1: HSI oscillator ready
Set and cleared by software.
Set by hardware to force the HSI oscillator ON when leaving the Stop or Standby mode or in
case of a failure of the HSE oscillator used directly or indirectly as the system clock. This bit
cannot be cleared if the HSI is used directly or indirectly as the system clock.
0: HSI oscillator OFF
1: HSI oscillator ON
RM0401 Rev 3
Reset and clock control (RCC)
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