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ATSAM4S-XPLD
210
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
12.10.1.1SysTick Control and Status
Name:
SYST_CSR
Access: Read-write
Reset: 0x000000000
The SysTick SYST_CSR register 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
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
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 register and then counts down. On reach-
ing 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.
ing 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
–
7
6
5
4
3
2
1
0
CLKSOURCE
TICKINT
ENABLE