
SysTick Registers
134
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Cortex-M4 Peripherals
2.3.1 STCTRL Register (Offset = 0x10) [reset = 0x0]
SysTick Control and Status Register (STCTRL)
NOTE:
This register can be accessed only from privileged mode.
The SysTick STCTRL register enables the SysTick features.
STCTRL is shown in
and described in
.
Return to
Figure 2-3. STCTRL Register
31
30
29
28
27
26
25
24
RESERVED
R-0x0
23
22
21
20
19
18
17
16
RESERVED
COUNT
R-0x0
R-0x0
15
14
13
12
11
10
9
8
RESERVED
R-0x0
7
6
5
4
3
2
1
0
RESERVED
CLK_SRC
INTEN
ENABLE
R-0x0
R/W-0x0
R/W-0x0
R/W-0x0
Table 2-11. STCTRL Register Field Descriptions
Bit
Field
Type
Reset
Description
31-17
RESERVED
R
0x0
16
COUNT
R
0x0
Count Flag
This bit is cleared by a read of the register or if the STCURRENT
register is written with any value. If read by the debugger using the
DAP, this bit is cleared only if the MasterType bit in the AHB-AP
Control Register is clear. Otherwise, the COUNT bit is not changed
by the debugger read. See the Arm Debug Interface V5 Architecture
Specification for more information on MasterType.
0x0 = The SysTick timer has not counted to 0 since the last time this
bit was read.
0x1 = The SysTick timer has counted to 0 since the last time this bit
was read.
15-3
RESERVED
R
0x0
2
CLK_SRC
R/W
0x0
Clock Source
0x0 = Precision internal oscillator (PIOSC) divided by 4
1 = System clock
1
INTEN
R/W
0x0
Interrupt Enable
0 = Interrupt generation is disabled. Software can use the COUNT
bit to determine if the counter has ever reached 0.
1 = An interrupt is generated to the NVIC when SysTick counts to 0.
0
ENABLE
R/W
0x0
Enable
0 = The counter is disabled.
1 = Enables SysTick to operate in a multi-shot way. That is, the
counter loads the RELOAD value and begins counting down. On
reaching 0, the COUNT bit is set and an interrupt is generated if
enabled by INTEN. The counter then loads the RELOAD value again
and begins counting.