Datasheet

LPC2109_2119_2129_5 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 05 — 7 March 2007 19 of 35
NXP Semiconductors
LPC2109/2119/2129
Single-chip 16/32-bit microcontrollers
• Four external outputs per timer corresponding to match registers, with the following
capabilities:
– Set LOW on match.
– Set HIGH on match.
– Toggle on match.
– Do nothing on match.
6.17 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.
6.17.1 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 pre-scaler.
• Selectable time period from (T
cy(PCLK)
× 256 × 4) to (T
cy(PCLK)
× 2
32
× 4) in multiples of
T
cy(PCLK)
× 4.
6.18 Real-time clock
The RTC is designed to provide a set of counters to measure time when normal or idle
operating mode is selected. The RTC has been designed to use little power, making it
suitable for battery powered systems where the CPU is not running continuously (Idle
mode).
6.18.1 Features
• Measures the passage of time to maintain a calendar and clock.
• Ultra low power design to support battery powered systems.
• Provides Seconds, Minutes, Hours, Day of Month, Month, Year, Day of Week, and
Day of Year.
• Programmable reference clock divider allows adjustment of the RTC to match various
crystal frequencies.