Datasheet

LPC2104_2105_2106_7 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 07 — 20 June 2008 20 of 41
NXP Semiconductors
LPC2104/2105/2106
Single-chip 32-bit microcontrollers
• Programmable 32-bit timer with internal pre-scaler.
• Selectable time period from (T
cy(PCLK)
× 256 × 4) to (T
cy(PCLK)
× 2
32
× 4) in multiples of
T
cy(PCLK)
× 4.
6.16 Real time clock
The Real Time Clock (RTC) is designed to provide a set of counters to measure time
when normal or idle operating mode is selected. The RTC has been designed to use little
power, making it suitable for battery powered systems where the CPU is not running
continuously (Idle mode).
6.16.1 Features
• Measures the passage of time to maintain a calendar and clock.
• Ultra Low Power design to support battery powered systems.
• 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 LPC2104/2105/2106. 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.
It also includes four capture inputs to save the timer value when an input signal transitions,
and optionally generate an interrupt when those events occur. The PWM function is in
addition to these features, and is 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.