Clock multiplexer of USART2 in STM32F051R8?

[ihartavi]

Dear all,

The MCU : STM32F051R8T on Discovery Board

Issue : USART1 and USART2 are required. The clock of USART1 can be configured by CubeMX. However, it is not possible for that of USART2

Details

1. The clock source of USART1 can be configured using USART1SW bits in RCC_CFGR3. This is clearly shown in reference manual rev.9 (page133)
2. The clock source of USART2 can be configured using USART2SW bits in RCC_CFGR3. This is clearly shown in reference manual rev.9, but, only for STM32F07x and STM32F09x devices (page132)
3. I made a check through the CubeMX and found:

This creates big confusion.

• No clock MUX for USART2 in F051, but, USART2 is there. So, which clock does it use?
• Both F070 and F072 have USART2. The latter has dedicated Mux, but, former.

I welcome any approximation, or explanation.

Thanks for help in advance!

Best regards!

[waclawek.jan]

> No clock MUX for USART2 in F051, but, USART2 is there. So, which clock does it use?

PCLK, i.e. APB clock.

> Both F070 and F072 have USART2. The latter has dedicated Mux, but, former[ not]

Accept it as a fact.

Note, that 'F0x0 have a separate RM, RM0360; whereas the non-zero-ending parts have RM0091.

JW

[ihartavi]

Thanks for the reply!