UM10429
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User manual
Rev. 1 — 20 October 2010
138 of 258
NXP Semiconductors
UM10429
Chapter 15: LPC1102 System tick timer
15.6.1 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
Section 19.5.4 “System timer, SysTick”
.
15.6.2 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.
15.6.3 System Timer Current value register
The SYST_CVR register returns the current count from the System Tick counter when it is
read by software.
15.6.4 System Timer Calibration value register (SYST_CALIB - 0xE000 E01C)
The value of the SYST_CALIB register is driven by the value of the SYSTCKCAL register
in the system configuration block (see
).
Table 136. 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, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA
Table 137. System Timer Current value register (SYST_CVR - 0xE000 E018) bit description
Bit
Symbol
Description
Reset
value
23:0
CURRENT Reading this register returns the current value of the System Tick
counter. Writing any value clears the System Tick counter and the
COUNTFLAG bit in STCTRL.
0
31:24
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
NA
Table 138. System Timer Calibration value register (SYST_CALIB - 0xE000 E01C) bit
description
Bit
Symbol
Value
Description
Reset
value
23:0
TENMS
<tbd>
0x4
29:24
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
NA
30
SKEW
<tbd>
0
31
NOREF
<tbd>
0