31.6 SysTick External Clock

When the processor selects the SysTick external clock, the calibration value is fixed to 150000. This allows the generation of a time base of 1 ms with the SysTick clock at the maximum frequency on HCLK divided by 2.

The SysTick counter may miss a number of counts if an external clock source is selected when entering the sleep mode.

Refer to the section “Arm Cortex-M7 Processor” for details on selecting the SysTick external clock.