Peripheral migration

AN4617

12/26

DocID027161 Rev 1

2.4

Reset and clock controller (RCC) interface

The main differences related to the RCC (Reset and clock controller) between the STM32F0

and the STM32L0 series are presented in Table 6.

Note:

NA = Not applicable - Feature not available

When migrating between STM32F0 and STM32L0 series user should respect the possible

system frequency limitations and check and update the setting if necessary:

a)

System clock frequency while respecting limits related to applied voltage range

b)

Flash parameters with respect to applied system frequency and voltage range

c)

PLL configuration in case PLL is used as the system clock source (L0 has no

implemented pre-divider on HSE, and programmable one on HSI PLL source input

paths).

Both F0 and L0 series running at maximum performance (system clock at 48 MHz / 32 MHz)

require Flash configured with 1 wait state.

Table 6. RCC differences between STM32F0 and STM32L0 series

RCC

STM32F0 series

STM32L0 series

MSI

NA

Multispeed internal RC clock

(default system clock at startup)

HSI14

High speed internal oscillator dedicated to ADC NA

HSI

8 MHz RC factory-trimmed

16 MHz RC factory-trimmed

HSI48

48 MHz RC clock (USB, PLL)

48 MHz RC clock (USB, RNG)

LSI

40 kHz RC

38 kHz RC

HSE

1 - 32 MHz

0 - 32 MHz

1 - 32 MHz with PLL or CSS

LSE

32.768 kHz

(RTC)

32.768 kHz

(RTC, LPTIMER, LCD, UARTs)

PLL

Main PLL

Main PLL

System clock

source

HSI, HSE or PLL (opt. HSI48)

HSI, MSI, HSE or PLL

System clock

frequency

Up to 48 MHz

Up to 32 / 16 / 4.2 MHz

(depending on power range)

APB1,2/APB

frequency

Up to 48 MHz

Up to 32 MHz

(depending on power range)

RTC clock source LSI, LSE or divided HSE

LSI, LSE or divided HSE

MCO clock source

MCO pin: (PA8)

SYSCLK, HSI, HSE, HSI14, PLLCLK/2,

LSE, LSI, (HSI48, PLL)

SYSCLK, HSI16, HSI48, MSI, HSE, PLL, LSI,

LSE

Internal oscillator

measurement /

calibration

LSE / LSI / HSI / HSI14 / HSI48 / HSE clocks

can be measured indirectly through MCO by

the timer TIM14 input capture channel 1 with

respect to HSI / HSE clock feeding the timer

LSE / LSI / MSI / HSE_RTC clocks can be

measured by the timer TIM21 input capture

channel 1 with respect to HSI / MSI / HSE

clock feeding the timer

Firewall internal

reset source

NA

Yes