NUMICRO-SDK Nuvoton Technology Corporation of America, NUMICRO-SDK Datasheet - Page 154

• Manufacturer Part Number: NUMICRO-SDK
• Description: KIT EVAUATION NUC100/120/130/140
• Manufacturer: Nuvoton Technology Corporation of America
• Series: NuMicro™r
• Type: MCUr

Specifications of NUMICRO-SDK

• Contents: Board, Cable, CD, Nu-Link
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: NUC100, NUC120, NUC130, NUC140

NuMicro™ NUC100 Series Technical Reference Manual
5.2.6
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 zero, 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 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 will 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 documents “ARM
Cortex™-M0 Technical
®
Reference Manual” and “ARM
v6-M Architecture Reference Manual”.
Publication Release Date: Dec. 22, 2010
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Revision V1.06