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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
54 of 808
NXP Semiconductors
UM10360
Chapter 4: LPC17xx Clocking and power control
8.7.1 Encoding of Reduced Power Modes
The PM1and PM0 bits in PCON allow entering reduced power modes as needed. The
encoding of these bits allows backward compatibility with devices that previously only
supported Sleep and Power-down modes.
below shows the encoding for the
three reduced power modes supported by the LPC17xx.
8.8 Wake-up from Reduced Power Modes
Any enabled interrupt can wake up the CPU from Sleep mode. Certain interrupts can
wake up the processor if it is in either Deep Sleep mode or Power-down mode.
Interrupts that can occur during Deep Sleep or Power-down mode will wake up the CPU if
the interrupt is enabled. After wake-up, execution will continue to the appropriate interrupt
service routine. These interrupts are NMI, External Interrupts EINT0 through EINT3, GPIO
interrupts, Ethernet Wake-on-LAN interrupt, Brownout Detect, and RTC Alarm. In addition,
the watchdog timer can wake up the part from Deep Sleep mode if the watchdog timer is
being clocked by the IRC oscillator.
Additional functions that can wake up the CPU from Deep Sleep or Power-down mode are
the CAN Activity Interrupt, generated by activity on the CAN bus pins, and the USB
Activity Interrupt, generated by activity on the USB bus pins. For the wake-up process to
take place, the related function must be mapped to a pin, and the corresponding interrupt
must be enabled.
8.9 Power Control for Peripherals register (PCONP - 0x400F C0C4)
The PCONP register allows turning off selected peripheral functions for the purpose of
saving power. This is accomplished by gating off the clock source to the specified
peripheral blocks. A few peripheral functions cannot be turned off (i.e. the Watchdog timer,
the Pin Connect block, and the System Control block).
Some peripherals, particularly those that include analog functions, may consume power
that is not clock dependent. These peripherals may contain a separate disable control that
turns off additional circuitry to reduce power. Information on peripheral specific power
saving features may be found in the chapter describing that peripheral.
Each bit in PCONP controls one peripheral as shown in
If a peripheral control bit is 1, that peripheral is enabled. If a peripheral control bit is 0, that
peripheral’s clock is disabled (gated off) to conserve power. For example if bit 19 is 1, the
I
2
C1 interface is enabled. If bit 19 is 0, the I
2
C1 interface is disabled.
Table 45.
Encoding of reduced power modes
PM1, PM0
Description
00
Execution of WFI or WFE enters either Sleep or Deep Sleep mode as defined
by the SLEEPDEEP bit in the Cortex-M3 System Control Register.
01
Execution of WFI or WFE enters Power-down mode if the SLEEPDEEP bit in
the Cortex-M3 System Control Register is 1.
10
Reserved, this setting should not be used.
11
Execution of WFI or WFE enters Deep Power-down mode if the SLEEPDEEP
bit in the Cortex-M3 System Control Register is 1.