RTC STM32F1xx

Calibration clock output

RTC clock calibration register (BKP_RTCCR). 

Bit 7 CCO: Calibration clock output

0: No effect

1: Setting this bit outputs the RTC clock with a frequency divided by 64 on the TAMPER pin.

The TAMPER pin must not be enabled while the CCO bit is set in order to avoid unwanted Tamper detection.

Note: This bit is reset when the V DD supply is powered off.

Event control register (AFIO_EVCR).

Bits 31:8 Reserved

Bit 7 EVOE: Event output enable
Set and cleared by software. When set the EVENTOUT Cortex output is connected to the
I/O selected by the PORT[2:0] and PIN[3:0] bits.

Bits 6:4 PORT[2:0]: Port selection
Set and cleared by software. Select the port used to output the Cortex EVENTOUT signal.
Note: The EVENTOUT signal output capability is not extended to ports PF and PG.
000: PA selected
001: PB selected
010: PC selected
011: PD selected
100: PE selected

Bits 3:0 PIN[3:0]: Pin selection (x = A .. E)
Set and cleared by software. Select the pin used to output the Cortex EVENTOUT signal.
0000: Px0 selected
0001: Px1 selected
0010: Px2 selected
0011: Px3 selected
...
1111: Px15 selected

Programm realisation for STM32F103:

AFIO->EVCR =0xAD; //PC13-calibration clock output enable
BKP->RTCCR |= BKP_RTCCR_CCO; //Setting this bit outputs the
//RTC clock with a frequency divided by 64 on the TAMPER pin