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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
301 of 368
NXP Semiconductors
UM10375
Chapter 18: LPC13xx WatchDog Timer (WDT)
18.7 Register description
The Watchdog contains four registers as shown in
below.
[1]
Reset Value reflects the data stored in used bits only. It does not include reserved bits content.
18.7.1 Watchdog Mode register (WDMOD - 0x4000 0000)
The WDMOD register controls the operation of the Watchdog through the combination of
WDEN and RESET bits. Note that a watchdog feed must be performed before any
changes to the WDMOD register take effect.
Once the
WDEN
and/or
WDRESET
bits are set they can not be cleared by software. Both
flags are cleared by reset or a Watchdog timer underflow.
WDTOF
The Watchdog time-out flag is set when the Watchdog times out. This flag is
cleared by software or any reset except the WDT reset.
WDINT
The Watchdog interrupt flag is set when the Watchdog times out. This flag is
cleared when any reset occurs. Once the watchdog interrupt is serviced, it can be
disabled in the NVIC or the watchdog interrupt request will be generated indefinitely. the
intent of the watchdog interrupt is to allow debugging watchdog activity without resetting
the device when the watchdog overflows.
Table 289. Register overview: Watchdog timer (base address 0x4000 4000)
Name
Access Address
offset
Description
Reset
Value
WDMOD
R/W
0x000
Watchdog mode register. This register contains the
basic mode and status of the Watchdog Timer.
0
WDTC
R/W
0x004
Watchdog timer constant register. This register
determines the time-out value.
0xFF
WDFEED
WO
0x008
Watchdog feed sequence register. Writing 0xAA
followed by 0x55 to this register reloads the
Watchdog timer with the value contained in WDTC.
NA
WDTV
RO
0x00C
Watchdog timer value register. This register reads
out the current value of the Watchdog timer.
0xFF
Table 290. Watchdog Mode register (WDMOD - address 0x4000 4000) bit description
Bit
Symbol
Description
Reset Value
0
WDEN
WDEN Watchdog enable bit (Set Only). When one, the
watchdog timer is running.
0
1
WDRESET WDRESET Watchdog reset enable bit (Set Only). When 1,
a watchdog time-out will cause a chip reset.
0
2
WDTOF
WDTOF Watchdog time-out flag. Set when the watchdog
timer times out, cleared by software.
0 (After any
reset except
WDT)
3
WDINT
WDINT Watchdog interrupt flag (Read Only, not clearable
by software).
0
7:4
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
-
31:8
-
reserved
-