Datasheet

LPC2377_78 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6.1 — 16 October 2013 30 of 69
NXP Semiconductors
LPC2377/78
Single-chip 16-bit/32-bit microcontrollers
7.23 Watchdog timer
The purpose of the watchdog is to reset the microcontroller within a reasonable amount of
time if it enters an erroneous state. When enabled, the watchdog will generate a system
reset if the user program fails to ‘feed’ (or reload) the watchdog within a predetermined
amount of time.
7.23.1 Features
• Internally resets chip if not periodically reloaded.
• Debug mode.
• Enabled by software but requires a hardware reset or a watchdog reset/interrupt to be
disabled.
• Incorrect/Incomplete feed sequence causes reset/interrupt if enabled.
• Flag to indicate watchdog reset.
• Programmable 32-bit timer with internal prescaler.
• Selectable time period from (T
cy(WDCLK)
 256  4) to (T
cy(WDCLK)
 2
32
 4) in
multiples of T
cy(WDCLK)
 4.
• The Watchdog Clock (WDCLK) source can be selected from the RTC clock, the
Internal RC oscillator (IRC), or the APB peripheral clock. This gives a wide range of
potential timing choices of watchdog operation under different power reduction
conditions. It also provides the ability to run the WDT from an entirely internal source
that is not dependent on an external crystal and its associated components and
wiring, for increased reliability.