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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
298 of 571
NXP Semiconductors
UM10316
Chapter 20: LPC29xx WatchDog Timer (WDT)
4.1 Watchdog timer-control register
The WTCR is used to control the operation of the timer counter. The Watchdog key - as
stored in the Watchdog Key register - is used to prevent unintentional control. This key
must be XOR-ed with the two control bits so that it is only possible to start the timer by
writing ‘251D 8951h’. All other values are ignored. Resetting the timer (e.g. just before
entering power-down mode) is only possible by writing ‘251D 8952h’. The counting
process starts on CLK_SAFE once the COUNTER_ENABLE bit is set. The process can
be reset by setting the COUNTER_RESET bit. The TC and TR remain in the reset state
for as long as the COUNTER_RESET bit is active.
FD4h
R
0000 00C8h
reserved
Reserved
FD8h
W
0000 0101h
INT_CLR_ENABLE
Interrupt clear-enable register
see
FDCh
W
-
INT_SET_ENABLE
Interrupt set-enable register
see
FE0h
R
0000 0000h
INT_STATUS
Interrupt status register
see
FE4h
R
0000 0000h
INT_ENABLE
interrupt enable register
see
FE8h
W
-
INT_CLR_STATUS
Interrupt clear-status register
see
FECh
W
-
INT_SET_STATUS
Interrupt set-status register
see
FFCh
R
3012 2900h
reserved
Reserved
Table 251. Watchdog timer register overview (base address 0xE004 0000)
Address
offset
Access
Reset value
Name
Description
Reference
Table 252. WTCR register bit description (WTCR, address: 0xE004 0000)
* = reset value
Bit
Variable name
Access
Value
Description
31 to 3
WD_KEY
R/W
Protection key, see above. Writes to the
WTCR register are ignored if a value other
than the Watchdog key is written to this
field, read as logic 0
0000
0000h*
2
PAUSE_ENABLE
R/W
1
Enables the pause feature of the
Watchdog timer. If this bit is set the
counters (timer and prescale counter) will
be stopped when the ARM processor is in
debug mode (connected to
ARM9_DBGACK)
0*