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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
478 of 808
NXP Semiconductors
UM10360
Chapter 23: LPC17xx System Tick Timer
5.
Register description
[1]
Reset Value reflects the data stored in used bits only. It does not include content of reserved bits.
5.1 System Timer Control and status register (STCTRL - 0xE000 E010)
The STCTRL register contains control information for the System Tick Timer, and provides
a status flag.
Fig 116. System Tick Timer block diagram
cclk
STCALIB
STRELOAD
STCURR
24-bit down counter
ENABLE
STCTRL
private
peripheral
bus
System Tick
interrupt
STCLK pin
CLKSOURCE
TICKINT
COUNTFLAG
load
under-
flow
count
enable
clock
D
Q
load data
Table 419. System Tick Timer register map
Name
Description
Access
Reset value
Address
STCTRL
System Timer Control and status register
R/W
0x4
0xE000 E010
STRELOAD
System Timer Reload value register
R/W
0
0xE000 E014
STCURR
System Timer Current value register
R/W
0
0xE000 E018
STCALIB
System Timer Calibration value register
R/W
0x000F 423F
0xE000 E01C
Table 420. System Timer Control and status register (STCTRL - 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 CPU clock is selected.
When 0, the external clock pin (STCLK) is selected.
1