System Timer (Systick) - Nuvoton ISD94124BYI Technical Reference Manual

Isd arm cortex-m4f soc

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6.2.12 System Timer (SysTick)

-M4 integrates a 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

(SYST_LOAD) on the next clock cycle, and then decrement on subsequent clocks. When the

counter decrements to zero, the COUNTFLAG status bit is set. A read or write on Current Value

The SYST_VAL 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_LOAD value

rather than an arbitrary value when it is enabled.

If the SYST_LOAD 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

v6-M Architecture Reference Manual".

6.2.12.1 System Timer Control Register Map

R: read only, W: write only, R/W: both read and write

SYST Base Address:

SCS_BA = 0xE000_E000

Any register not listed here is reserved and must not be written. The result of a read operation on these bits is undefined.

The reserved register fields that listed in register description must be written to their reset value. Writing reserved fields with

other than reset values may produce undefined results.

ISD94100 Series Technical Reference Manual

R/W Description

R/W SysTick Control and Status Register

R/W SysTick Reload Value Register

R/W SysTick Current Value Register

Page 98 of 928

Cortex™-M4 Technical Reference Manual"

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