UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
918 of 1269
34.1 How to read this chapter
The WWDT is available on all LPC43xx parts.
34.2 Basic configuration
The WWDT is configured as follows:
•
See
for clocking and power control. The only clock source for the WWDT
clock (WDCLK) is the IRC.
•
The WWDT cannot be reset by software.
•
The WWDT interrupt is connected to slot # 7 in the Event router and slot #49 in the
M4 NVIC.
•
The branch clock CLK_M4_WWDT must be enabled to trigger the WWDT interrupt.
•
The WWDT registers can be accessed by the GPDMA as memory-to-memory
transfer.
34.3 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 reset if enabled.
•
The watchdog reload value can optionally be protected such that it can only be
changed after the “warning interrupt” time is reached.
UM10503
Chapter 34: LPC43xx Windowed Watchdog timer (WWDT)
Rev. 1.3 — 6 July 2012
User manual
Table 771. WWDT clocking and power control
Base clock
Branch clock
Operating
frequency
Notes
Clock to WWDT register interface
(PCLK)
BASE_M4_CLK
CLK_M4_WWDT up to 204 MHz
Enable this branch
clock when the WWDT
is running.
Watchdog clock (WDCLK)
BASE_SAFE_CLK
-
12 MHz (fixed
frequency)
-