4.4.2. SysTick Reload Value Register

The SYST_RVR register specifies the start value to load into the SYST_CVR register. See the register summary in Table 4.33 for its attributes. The bit assignments are:

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Table 4.35. SYST_RVR bit assignments

BitsNameFunction
[31:24]-Reserved
[23:0]RELOADValue to load into the SYST_CVR register when the counter is enabled and when it reaches 0, see Calculating the RELOAD value

Calculating the RELOAD value

The RELOAD value can be any value in the range 0x00000001-0x00FFFFFF. A start value of 0 is possible, but has no effect because the SysTick exception request and COUNTFLAG are activated when counting from 1 to 0.

The RELOAD value is calculated according to its use. For example, to generate a multi-shot timer with a period of N processor clock cycles, use a RELOAD value of N-1. If the SysTick interrupt is required every 100 clock pulses, set RELOAD to 99.

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