LPC2212 datasheet(21/45 Pages) PHILIPS

21 / 45 page

LPC2212_2214_4

Product data sheet

Rev. 04 — 3 January 2008

21 of 45

NXP Semiconductors

LPC2212/2214

16/32-bit ARM microcontrollers

• 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.

6.17 Pulse width modulator

The PWM is based on the standard Timer block and inherits all of its features, although

only the PWM function is pinned out on the LPC2212/2214. The Timer is designed to

count cycles of the peripheral clock (PCLK) and optionally generate interrupts or perform

other actions when speciﬁed timer values occur, based on seven match registers. The

PWM function is also based on match register events.

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 (MR0) 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 MR0 match occurs.

Three match registers can be used to provide a PWM output with both edges controlled.

Again, the MR0 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).

6.17.1 Features

• Seven match registers allow up to six single edge controlled or three 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.

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