Reset and clock control (RCC) RM0453
310/1450 RM0453 Rev 5
7.4.2 RCC internal clock sources calibration register (RCC_ICSCR)
Address offset: 0x004
Reset value: 0x40XX 00XX
The reset value of HSICAL[7:0] and MSICAL[7:0] is factory-programmed.
Access: no wait state, word, half-word and byte access
Bit 0 MSION: MSI clock enable
This bit is set and cleared by software. It is also cleared by hardware to stop the MSI
oscillator when entering Stop, Standby or Shutdown mode. This bit is set by hardware to
force the MSI oscillator on when exiting Standby or Shutdown mode. It is set by hardware to
force the MSI oscillator on when STOPWUCK = 0 when exiting from Stop modes, or in case
of a HSE32 oscillator failure. This bit is set by hardware when used directly or indirectly as
system clock. It cannot be reset if the MSI oscillator is used directly or indirectly as system
clock.
0: MSI oscillator off
1: MSI oscillator on
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res. HSITRIM[6:0] HSICAL[7:0]
rwrwrwrwrwrwrwrrrrrr r r
1514131211109 8 765432 1 0
MSITRIM[7:0] MSICAL[7:0]
rwrwrwrwrwrwrwrwrrrrrr r r
Bit 31 Reserved, must be kept at reset value.
Bits 30:24 HSITRIM[6:0]: HSI16 clock trimming
These bits provide an additional user-programmable trimming value that is added to the
HSICAL[7:0] bits. They can be programmed to adjust to variations in voltage and
temperature that influence the HSI16 frequency.
The default value is 64 that, when added to the HSICAL value, must trim the HSI16 to
16 MHz ± 1 %.
Bits 23:16 HSICAL[7:0]: HSI16 clock calibration
These bits are initialized at startup with the factory-programmed HSI16 calibration trim value.
When HSITRIM is written, HSICAL is updated with the sum of HSITRIM and the factory trim
value.
Bits 15:8 MSITRIM[7:0]: MSI clock trimming
These bits provide an additional user-programmable trimming value that is added to the
MSICAL[7:0] bits. It can be programmed to adjust to variations in voltage and temperature
that influence the frequency of the MSI.
The default value is 0, that, when added to the MSICAL value, must trim the MSI to its mid
frequency.
Bits 7:0 MSICAL[7:0]: MSI clock calibration
These bits are initialized at startup with the factory-programmed MSI calibration trim value.
When MSITRIM is written, MSICAL is updated with the sum of MSITRIM and the factory trim
value.
Note: Adding a MSITRIM value with the MSB set results in a subtraction.
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