Datasheet

227
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
12.10.1.1 SysTick Control and Status
Name: SYST_CSR
Access: Read/Write
Reset: 0x000000000
The SysTick SYST_CSR enables the SysTick features.
COUNTFLAG: Count Flag
Returns 1 if the timer counted to 0 since the last time this was read.
CLKSOURCE: Clock Source
Indicates the clock source:
0: External Clock.
1: Processor Clock.
TICKINT: SysTick Exception Request Enable
Enables a SysTick exception request:
0: Counting down to zero does not assert the SysTick exception request.
1: Counting down to zero asserts the SysTick exception request.
The software can use COUNTFLAG to determine if SysTick has ever counted to zero.
ENABLE: Counter Enable
Enables the counter:
0: Counter disabled.
1: Counter enabled.
When ENABLE is set to 1, the counter loads the RELOAD value from the SYST_RVR and then counts down. On reaching 0, it
sets the COUNTFLAG to 1 and optionally asserts the SysTick depending on the value of TICKINT. It then loads the RELOAD
value again, and begins counting.
31 30 29 28 27 26 25 24
23 22 21 20 19 18 17 16
COUNTFLAG
15 14 13 12 11 10 9 8
76543210
CLKSOURCE TICKINT ENABLE