Use the SysTick Reload Value Register to specify the start value to load into the current value register when the counter reaches 0. It can be any value between 0 and 0x00FFFFFF. A start value of 0 is possible, but has no effect because the SysTick interrupt and COUNTFLAG are activated when counting from 1 to 0. The reset value of this register is UNKNOWN. To generate a multi-shot timer with a period of N processor clock cycles, use a RELOAD value of N-1. For example, if the SysTick interrupt is required every 100 clock pulses, set RELOAD to 99.
RELOAD | Value to load into the SysTick Current Value Register when the counter reaches 0. |