UM10850
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User manual
Rev. 2.4 — 13 September 2016
251 of 464
NXP Semiconductors
UM10850
Chapter 19: LPC5410x CPU system tick timer (SYSTICK)
19.5 Register description
The systick timer registers are located on the private peripheral bus of each CPU (see
[1]
Reset Value reflects the data stored in used bits only. It does not include content of reserved bits.
19.5.1 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 CPU.
This register determines the clock source for the system tick timer.
19.5.2 System Timer Reload value register
The SYST_RVR register is set to the value that will be loaded into the SysTick timer
whenever it counts down to zero. This register is loaded by software as part of timer
initialization. The SYST_CALIB register may be read and used as the value for
SYST_RVR register if the CPU is running at the frequency intended for use with the
SYST_CALIB value.
Table 296. 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
0
SYST_RVR
R/W
0x014
System Timer Reload value register
0
SYST_CVR
R/W
0x018
System Timer Current value register
0
SYST_CALIB
RO
0x01C
System Timer Calibration value register
0
Table 297. SysTick Timer Control and status register (SYST_CSR - 0xE000 E010) bit description
Bit
Symbol
Description
Reset
value
0
ENABLE
System Tick counter enable. When 1, the counter is enabled. When 0, the counter is
disabled.
0
1
TICKINT
System Tick interrupt enable. When 1, the System Tick interrupt is enabled. When 0, the
System Tick interrupt is disabled. When enabled, the interrupt is generated when the
System Tick counter counts down to 0.
0
2
CLKSOURCE
System Tick clock source selection. When 1, the system clock is selected. When 0, the
output clock from the system tick clock divider (SYSTICKCLKDIV, see
and
) is selected as the reference clock.
Remark:
When the system tick clock divider is selected as the clock source, the CPU clock
must be at least 2.5 times faster than the divider output.
0
15:3
-
Reserved. Read value is undefined, only zero should be written.
NA
16
COUNTFLAG
Returns 1 if the SysTick timer counted to 0 since the last read of this register.
0
31:17
-
Reserved. Read value is undefined, only zero should be written.
NA
Table 298. System Timer Reload value register (SYST_RVR - 0xE000 E014) bit description
Bit
Symbol
Description
Reset
value
23:0
RELOAD
This is the value that is loaded into the System Tick counter when it counts down to 0.
0
31:24
-
Reserved. Read value is undefined, only zero should be written.
NA