M058SFAN Datasheet, PDF (29/72 Pages) List of Unclassifed Manufacturers – 32-bit Microcontroller

NuMicro M058S Series Datasheet
6.2.6 System Timer (SysTick)
The Cortex^® -M0 includes an integrated system timer, SysTick. SysTick 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 0, and reload (wrap) to the value in the SysTick Reload Value Register
(SYST_RVR) on the next clock edge, then decrement on subsequent clocks. When the counter
transitions to 0, 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 will count from the SYST_RVR value
rather than an arbitrary value when it is enabled.
If the SYST_RVR is 0, the timer will be maintained with a current value of 0 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 documents “ARM^® Cortex^® -M0 Technical
Reference Manual” and “ARM^® v6-M Architecture Reference Manual”.
Nov. 27, 2014
Page 29 of 72
Rev.1.03