ISD94100 Series Technical Reference Manual
Sep 9, 2019
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6.2.12.2 System Timer Control Register Description
SysTick Control and Status Register (SYST_CTRL)
Register
Offset
R/W Description
Reset Value
SYST_CTRL
0x10
R/W SysTick Control and Status Register
0x0000_0000
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
COUNTFLAG
15
14
13
12
11
10
9
8
Reserved
7
6
5
4
3
2
1
0
Reserved
CLKSRC
TICKINT
ENABLE
Bits
Description
[31:17]
Reserved
Reserved. Any values read should be ignored. When writing to this field always write with
reset value.
[16]
COUNTFLAG
System Tick Counter Flag
Returns 1 if timer counted to 0 since last time this register was read.
COUNTFLAG is set by a count transition from 1 to 0.
COUNTFLAG is cleared on read or by a write to the Current Value register.
[15:3]
Reserved
Reserved. Any values read should be ignored. When writing to this field always write with
reset value.
[2]
CLKSRC
System Tick Clock Source Selection
0 = Clock source is the (optional) external reference clock.
1 = Core clock used for SysTick.
[1]
TICKINT
System Tick Interrupt Enabled
0 = Counting down to 0 does not cause the SysTick exception to be pended. Software can
use COUNTFLAG to determine if a count to zero has occurred.
1 = Counting down to 0 will cause the SysTick exception to be pended. Clearing the SysTick
current value register by a register write in software will not cause SysTick to be pended.
[0]
ENABLE
System Tick Counter Enabled
0 = Counter Disabled.
1 = Counter will operate in a multi-shot manner.
