MINI58LDE Datasheet, PDF (38/83 Pages) List of Unclassifed Manufacturers – 32-bit Microcontroller

MINI58DE
6.2.7 System Timer (SysTick)
The Cortex^® -M0 includes an integrated system timer, SysTick, which provides a simple, 24-bit
clear-on-write, decrementing, wrap-on-zero counter with a flexible control mechanism. The
counter can be used as a Real Time Operating System (RTOS) tick timer or as a simple counter.
When system timer is enabled, it will count down from the value in the SysTick Current Value
Register (SYST_CVR) to zero, and reload (wrap) to the value in the SysTick Reload Value
Register (SYST_RVR) on the next clock edge, and then decrement on subsequent clocks. When
the counter transitions to zero, the COUNTFLAG status bit is set. The COUNTFLAG bit clears on
reads.
The SYST_CVR value is UNKNOWN on reset. Software should write to the register to clear it to
zero before enabling the feature. This ensures the timer to count from the SYST_RVR value
rather than an arbitrary value when it is enabled.
If the SYST_RVR is zero, the timer will be maintained with a current value of zero after it is
reloaded with this value. This mechanism can be used to disable the feature independently from
the timer enable bit.
For more detailed information, please refer to the “ARM^® Cortex^® -M0 Technical Reference
Manual” and “ARM^® v6-M Architecture Reference Manual”.
Dec. 09, 2015
Page 38 of 83
Rev.1.02