UM10462
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User manual
Rev. 5.5 — 21 December 2016
380 of 523
NXP Semiconductors
UM10462
Chapter 18: LPC11U3x/2x/1x System tick timer
Since the SysTick timer is a part of the Cortex-M0, it facilitates porting of software by
providing a standard timer that is available on Cortex-M0 based devices. The SysTick
timer can be used for:
•
An RTOS tick timer which fires at a programmable rate (for example 100 Hz) and
invokes a SysTick routine.
•
A high-speed alarm timer using the core clock.
•
A simple counter. Software can use this to measure time to completion and time used.
•
An internal clock source control based on missing/meeting durations. The
COUNTFLAG bit-field in the control and status register can be used to determine if an
action completed within a set duration, as part of a dynamic clock management
control loop.
Refer to the
Cortex-M0 User Guide
for details.
18.5 Register description
The systick timer registers are located on the ARM Cortex-M0 private peripheral bus (see
), and are part of the ARM Cortex-M0 core peripherals. For details, see
[1]
Reset Value reflects the data stored in used bits only. It does not include content of reserved bits.
18.5.1 System Timer Control and status register
The SYST_CSR register contains control information for the SysTick timer and provides a
status flag. This register is part of the ARM Cortex-M0 core system timer register block.
For a bit description of this register, see
.
This register determines the clock source for the system tick timer.
Table 345. Register overview: SysTick timer (base address 0xE000 E000)
Name
Access
Address
offset
Description
Reset value
Reference
SYST_CSR
R/W
0x010
System Timer Control and status register
0x000 0000
SYST_RVR
R/W
0x014
System Timer Reload value register
0
SYST_CVR
R/W
0x018
System Timer Current value register
0
SYST_CALIB
R/W
0x01C
System Timer Calibration value register
0x4