### SysTick_CTRL

Bit Field | Read/Write | Field Name | Description
--- | --- | --- | ---
16 | R | COUNTFLAG | Reads as 1 if SYSTICK counter has reached 0 since the last time the timer has reached 0. Clears to 0 on read.
2 | RW | CLKSOURCE | SYSTICK timer clock source
1 | RW | TICKINT | SYSTICK timer interrupt enable
0 | RW | ENABLE | SYSTICK timer enable

Bit Field | Field Name | Value Symbol | Value Description | Hex Value
--- | --- | --- | --- | ---
16 | COUNTFLAG | SYSTICK_COUNTFLAG_NOT_ZERO | SYSTICK counter has not reached zero since last read | 0x0*
|  | SYSTICK_COUNTFLAG_ZERO | SYSTICK counter has reached zero since last read | 0x1
2 | CLKSOURCE | SYSTICK_CLKSOURCE_EXTREF_CLK | Use external reference clock (STCLK) | 0x0*
|  | SYSTICK_CLKSOURCE_CORE_CLK | Use the core clock | 0x1
1 | TICKINT | SYSTICK_TICKINT_DISABLE | Disable interrupt generation when SYSTICK timer reaches 0 | 0x0*
|  | SYSTICK_TICKINT_ENABLE | Enable interrupt generation when SYSTICK timer reaches 0 | 0x1
0 | ENABLE | SYSTICK_DISABLE | Disable SYSTICK timer | 0x0*
|  | SYSTICK_ENABLE | Enable SYSTICK Timer | 0x1