lpc1778 NXP Semiconductors, lpc1778 Datasheet - Page 61

• Manufacturer Part Number: lpc1778
• Description: 32-bit Arm Cortex-m3 Microcontroller; Up To 512 Kb Flash And 96 Kb Sram; Usb Device/host/otg; Ethernet; Lcd; Emc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC178x_7x
Objective data sheet
7.28.1 Features
7.27 Motor control PWM
7.28 Quadrature Encoder Interface (QEI)
7.29 ARM Cortex-M3 system tick timer
7.30 Windowed WatchDog Timer (WWDT)
The LPC178x/7x contain one motor control PWM.
The motor control PWM is a specialized PWM supporting 3-phase motors and other
combinations. Feedback inputs are provided to automatically sense rotor position and use
that information to ramp speed up or down. An abort input is also provided that causes the
PWM to immediately release all motor drive outputs. At the same time, the motor control
PWM is highly configurable for other generalized timing, counting, capture, and compare
applications.
Remark: The QEI is available on parts LPC1788/87/86 and LPC1778/77/76
A quadrature encoder, also known as a 2-channel incremental encoder, converts angular
displacement into two pulse signals. By monitoring both the number of pulses and the
relative phase of the two signals, the user can track the position, direction of rotation, 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.
The ARM Cortex-M3 includes a system tick timer (SYSTICK) that is intended to generate
a dedicated SYSTICK exception at a 10 ms interval. In the LPC178x/7x, this timer can be
clocked from the internal AHB clock or from a device pin.
The purpose of the watchdog is to reset the controller if software fails to periodically
service it within a programmable time window.
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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).
Connected to APB.
All information provided in this document is subject to legal disclaimers.
Rev. 00.04 — 8 July 2010
32-bit ARM Cortex-M3 microcontroller
LPC178x/7x
© NXP B.V. 2010. All rights reserved.
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