Datasheet
LPC1850_30_20_10 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 6.4 — 18 August 2014 77 of 150
NXP Semiconductors
LPC1850/30/20/10
32-bit ARM Cortex-M3 microcontroller
and velocity. In addition, a third channel, or index signal, can be used to reset the position
counter. The quadrature encoder interface decodes the digital pulses from a quadrature
encoder wheel to integrate position over time and determine direction of rotation. In
addition, the QEI can capture the velocity of the encoder wheel.
7.15.3.1 Features
• Tracks encoder position.
• Increments/decrements depending on direction.
• Programmable for 2 or 4 position counting.
• Velocity capture using built-in timer.
• Velocity compare function with “less than” interrupt.
• Uses 32-bit registers for position and velocity.
• Three position-compare registers with interrupts.
• Index counter for revolution counting.
• Index compare register with interrupts.
• Can combine index and position interrupts to produce an interrupt for whole and
partial revolution displacement.
• Digital filter with programmable delays for encoder input signals.
• Can accept decoded signal inputs (clk and direction).
7.15.4 Repetitive Interrupt (RI) timer
The repetitive interrupt timer provides a free-running 32-bit counter which is compared to
a selectable value, generating an interrupt when a match occurs. Any bits of the timer
compare function can be masked such that they do not contribute to the match detection.
The repetitive interrupt timer can be used to create an interrupt that repeats at
predetermined intervals.
7.15.4.1 Features
• 32-bit counter. Counter can be free-running or be reset by a generated interrupt.
• 32-bit compare value.
• 32-bit compare mask. An interrupt is generated when the counter value equals the
compare value, after masking. This mechanism allows for combinations not possible
with a simple compare.
7.15.5 Windowed WatchDog Timer (WWDT)
The purpose of the watchdog is to reset the controller if software fails to periodically
service it within a programmable time window.
7.15.5.1 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.