Datasheet

LPC111X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 9.2 — 26 March 2014 52 of 127
NXP Semiconductors
LPC1110/11/12/13/14/15
32-bit ARM Cortex-M0 microcontroller
• 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 24-bit timer with internal prescaler.
• Selectable time period from (T
cy(WDCLK)
 256  4) to (T
cy(WDCLK)
 2
24
 4) in
multiples of T
cy(WDCLK)
 4.
• The Watchdog Clock (WDCLK) source can be selected from the Internal RC oscillator
(IRC), the Watchdog oscillator, or the main 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.
7.15 Windowed WatchDog Timer (LPC1100L and LPC1100XL series)
Remark: The windowed watchdog timer is available on the LPC1100L and LPC1100XL
series only.
The purpose of the watchdog is to reset the controller if software fails to periodically
service it within a programmable time window.
7.15.1 Features
• Internally resets chip if not periodically reloaded during the programmable time-out
period.
• Optional windowed operation requires reload to occur between a minimum and
maximum time period, both programmable.
• Optional warning interrupt can be generated at a programmable time prior to
watchdog time-out.
• Enabled by software but requires a hardware reset or a watchdog reset/interrupt to be
disabled.
• Incorrect feed sequence causes reset or interrupt if enabled.
• Flag to indicate watchdog reset.
• Programmable 24-bit timer with internal prescaler.
• Selectable time period from (T
cy(WDCLK)
 256  4) to (T
cy(WDCLK)
 2
24
 4) in
multiples of T
cy(WDCLK)
 4.
• The Watchdog Clock (WDCLK) source can be selected from the IRC or the dedicated
watchdog oscillator (WDO). This gives a wide range of potential timing choices of
watchdog operation under different power conditions.
7.16 Clocking and power control
7.16.1 Crystal oscillators
The LPC1110/11/12/13/14/15 include three independent oscillators. These are the system
oscillator, the Internal RC oscillator (IRC), and the Watchdog oscillator. Each oscillator can
be used for more than one purpose as required in a particular application.