DRAFT
DRAFT DRAFT DR
DRAFT DRAFT DRAFT
D
RAF
DRAFT DRAFT DRA
FT D
RAFT DR
AFT D
DRA
FT DRAFT DRAFT
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DRAFT
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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
146 of 313
12.1 How to read this chapter
The watchdog timer is identical on all LPC800 parts.
12.2 Features
•
Internally resets chip if not reloaded during the programmable time-out period.
•
Optional windowed operation requires reload to occur between a minimum and
maximum time-out period, both programmable.
•
Optional warning interrupt can be generated at a programmable time prior to
watchdog time-out.
•
Programmable 24-bit timer with internal fixed pre-scaler.
•
Selectable time period from 1,024 watchdog clocks (T
WDCLK
256
4) to over 67
million watchdog clocks (T
WDCLK
2
24
4) in increments of 4 watchdog clocks.
•
“Safe” watchdog operation. Once enabled, requires a hardware reset or a Watchdog
reset to be disabled.
•
Incorrect feed sequence causes immediate watchdog event if enabled.
•
The watchdog reload value can optionally be protected such that it can only be
changed after the “warning interrupt” time is reached.
•
Flag to indicate Watchdog reset.
•
The Watchdog clock (WDCLK) source is the WatchDog oscillator.
•
The Watchdog timer can be configured to run in Deep-sleep or Power-down mode.
•
Debug mode.
12.3 Basic configuration
The WWDT is configured through the following registers:
•
Power to the register interface (WWDT PCLK clock): In the SYSAHBCLKCTRL
register, set bit 17 in
•
Enable the WWDT clock source (the watchdog oscillator) in the PDRUNCFG register
(
). This is the clock source for the timer base.
•
For waking up from a WWDT interrupt, enable the watchdog interrupt for wake-up in
the STARTERP1 register (
12.4 Pin description
The WWDT has no external pins.
UM10601
Chapter 12: LPC800 Windowed Watchdog Timer (WWDT)
Rev. 1.0 — 7 November 2012
Preliminary user manual