
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
317 of 487
20.1 How to read this chapter
The SysTick timer is available on all LPC82x parts.
20.2 Features
•
Simple 24-bit timer.
•
Uses dedicated exception vector.
•
Clocked internally by the system clock or the system clock/2.
20.3 Basic configuration
The system tick timer is configured using the following registers:
1. The system tick timer is enabled through the SysTick control register (
system tick timer clock is fixed to half of the system clock frequency.
2. Enable the clock source for the SysTick timer in the SYST_CSR register (
3. The calibration value of the SysTick timer is contained in the SYSTCKCAL register in
the system configuration block SYSCON (see
).
20.4 Pin description
The SysTick has no configurable pins.
20.5 General description
The block diagram of the SysTick timer is shown in
.
UM10800
Chapter 20: LPC82x System tick timer (SysTick)
Rev. 1.2 — 5 October 2016
User manual
Fig 51. System tick timer block diagram
system clock
reference clock
= system clock/2
SYST_CALIB
SYST_RVR
SYST_CVR
24-bit down counter
ENABLE
SYST_CSR
private
peripheral
bus
System Tick
interrupt
TICKINT
COUNTFLAG
load
under -
flow
count
enable
clock
load data
1
0
SYST_CSR
bit CLKSOURCE