© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
User manual
Rev. 01 — 15 August 2005
35
Philips Semiconductors
UM10139
Volume 1
Chapter 3: System Control Block
3.9 Power control
The LPC2141/2/4/6/8 supports two reduced power modes: Idle mode and Power-down
mode. In Idle mode, execution of instructions is suspended until either a Reset or interrupt
occurs. Peripheral functions continue operation during Idle mode and may generate
interrupts to cause the processor to resume execution. Idle mode eliminates power used
by the processor itself, memory systems and related controllers, and internal buses.
In Power-down mode, the oscillator is shut down and the chip receives no internal clocks.
The processor state and registers, peripheral registers, and internal SRAM values are
preserved throughout Power-down mode and the logic levels of chip pins remain static.
The Power-down mode can be terminated and normal operation resumed by either a
Reset or certain specific interrupts that are able to function without clocks. Since all
dynamic operation of the chip is suspended, Power-down mode reduces chip power
consumption to nearly zero.
Entry to Power-down and Idle modes must be coordinated with program execution.
Wakeup from Power-down or Idle modes via an interrupt resumes program execution in
such a way that no instructions are lost, incomplete, or repeated. Wake up from
Power-down mode is discussed further in
Section 3.12 “Wakeup timer” on page 41
A Power Control for Peripherals feature allows individual peripherals to be turned off if
they are not needed in the application, resulting in additional power savings.
3.9.1 Register
description
The Power Control function contains two registers, as shown in
. More detailed
descriptions follow.
[1]
Reset value reflects the data stored in used bits only. It does not include reserved bits content.
3.9.2 Power
Control
register (PCON - 0xE01F COCO)
The PCON register contains two bits. Writing a one to the corresponding bit causes entry
to either the Power-down or Idle mode. If both bits are set, Power-down mode is entered.
Table 24:
Power control registers
Name
Description
Access Reset
value
Address
PCON
Power Control Register. This register contains
control bits that enable the two reduced power
operating modes of the microcontroller. See
.
R/W
0x00
0xE01F C0C0
PCONP Power Control for Peripherals Register. This
register contains control bits that enable and
disable individual peripheral functions,
Allowing elimination of power consumption by
peripherals that are not needed.
R/W
0x0018 17BE
0xE01F C0C4