Reset and clock control (RCC) RM0390
126/1328 RM0390 Rev 4
Internal/external clock measurement using TIM11 channel1
TIM11 has an input multiplexer which allows choosing whether the input capture is triggered
by the I/O, by SPDIF-Rx Frame Synch or by an internal clock. This selection is performed
through TI1_RMP [1:0] bits in the TIM11_OR register. The HSE_RTC clock (HSE divided by
a programmable prescaler) is connected to channel 1 input capture to have a rough
indication of the external crystal frequency. This requires that the HSI is the system clock
source. This can be useful for instance to ensure compliance with the IEC 60730/IEC 61335
standards which require to be able to determine harmonic or subharmonic frequencies (–
50/+100% deviations).
Figure 17. Frequency measurement with TIM11 in Input capture mode
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