lpc1778 NXP Semiconductors, lpc1778 Datasheet - Page 60

• 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
7.26.1 Features
The ability to separately control rising and falling edge locations allows the PWM to be
used for more applications. For instance, multi-phase motor control typically requires
three non-overlapping PWM outputs with individual control of all three pulse widths and
positions.
Two match registers can be used to provide a single edge controlled PWM output. One
match register (PWMMR0) controls the PWM cycle rate, by resetting the count upon
match. The other match register controls the PWM edge position. Additional single edge
controlled PWM outputs require only one match register each, since the repetition rate is
the same for all PWM outputs. Multiple single edge controlled PWM outputs will all have a
rising edge at the beginning of each PWM cycle, when an PWMMR0 match occurs.
Three match registers can be used to provide a PWM output with both edges controlled.
Again, the PWMMR0 match register controls the PWM cycle rate. The other match
registers control the two PWM edge positions. Additional double edge controlled PWM
outputs require only two match registers each, since the repetition rate is the same for all
PWM outputs.
With double edge controlled PWM outputs, specific match registers control the rising and
falling edge of the output. This allows both positive going PWM pulses (when the rising
edge occurs prior to the falling edge), and negative going PWM pulses (when the falling
edge occurs prior to the rising edge).
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LPC178x/7x has two PWM blocks with Counter or Timer operation (may use the
peripheral clock or one of the capture inputs as the clock source).
Seven match registers allow up to 6 single edge controlled or 3 double edge
controlled PWM outputs, or a mix of both types. The match registers also allow:
– Continuous operation with optional interrupt generation on match.
– Stop timer on match with optional interrupt generation.
– Reset timer on match with optional interrupt generation.
Supports single edge controlled and/or double edge controlled PWM outputs. Single
edge controlled PWM outputs all go high at the beginning of each cycle unless the
output is a constant low. Double edge controlled PWM outputs can have either edge
occur at any position within a cycle. This allows for both positive going and negative
going pulses.
Pulse period and width can be any number of timer counts. This allows complete
flexibility in the trade-off between resolution and repetition rate. All PWM outputs will
occur at the same repetition rate.
Double edge controlled PWM outputs can be programmed to be either positive going
or negative going pulses.
Match register updates are synchronized with pulse outputs to prevent generation of
erroneous pulses. Software must ‘release’ new match values before they can become
effective.
May be used as a standard 32-bit timer/counter with a programmable 32-bit prescaler
if the PWM mode is not enabled.
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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