LPC2939 NXP Semiconductors, LPC2939 Datasheet - Page 49

• Manufacturer Part Number: LPC2939
• Description: The LPC2939 combine an ARM968E-S CPU core with two integrated TCM blocksoperating at frequencies of up to 125 MHz, Full-speed USB 2
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2939_3
Product data sheet
6.15.6.1 Pin description
6.15.6.2 Clock description
6.15.7 Quadrature Encoder Interface (QEI)
MSCSS timer 0 has no external pins.
MSCSS timer 1 has a PAUSE pin available as external pin. The PAUSE pin is combined
with other functions on the port pins of the LPC2939.
external pin.
Table 25.
The Timer modules in the MSCSS are clocked by CLK_MSCSS_MTMRx (x = 0 to 1), see
Section
power management. The frequency of all these clocks is identical to CLK_MSCSS_APB
since they are derived from the same base clock BASE_MSCSS_CLK.
Note that, unlike the timer modules in the Peripheral SubSystem, the actual timer counter
registers run at the same clock as the APB system interface CLK_MSCSS_APB. This
clock is independent of the AHB system clock.
If a timer module is not used its CLK_MSCSS_MTMRx branch clock can be switched off.
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 QEI has the following features:
Symbol
MSCSS PAUSE
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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
6.7.2. Note that each timer has its own CLK_MSCSS_MTMRx branch clock for
MSCSS timer 1 pin
All information provided in this document is subject to legal disclaimers.
Direction
IN
Rev. 03 — 7 April 2010
Description
pause pin for MSCSS timer 1
ARM9 microcontroller with CAN, LIN, and USB
Table 25
shows the MSCSS timer 1
LPC2939
© NXP B.V. 2010. All rights reserved.
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