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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
52 of 808
NXP Semiconductors
UM10360
Chapter 4: LPC17xx Clocking and power control
Upon wake-up from Power-down mode, if the IRC was used before entering Power-down
mode, after IRC-start-up time (about 60
μ
s), the 2-bit IRC timer starts counting and
expiring in 4 cycles. Code execution can then be resumed immediately following the
expiration of the IRC timer if the code was running from SRAM. In the meantime, the flash
wake-up timer measures flash start-up time of about 100
μ
s. When it times out, access to
the flash is enabled. The user must remember to re-configure any required PLLs and
clock dividers after the wake-up.
Wake-up from Power-down mode can be brought about by NMI, External Interrupts EINT0
through EINT3, GPIO interrupts, the Ethernet Wake-on-LAN interrupt, Brownout Detect,
an RTC Alarm interrupt, a USB input pin transition (USB activity interrupt), or a CAN input
pin transition, when the related interrupt is enabled.
8.4 Deep Power-down mode
In Deep Power-down mode, power is shut off to the entire chip with the exception of the
Real-Time Clock, the RESET pin, the WIC, and the RTC backup registers. Entry to Deep
Power-down mode causes the DPDFLAG bit in PCON to be set, see
.
To optimize power conservation, the user has the additional option of turning off or
retaining power to the 32 kHz oscillator. It is also possible to use external circuitry to turn
off power to the on-chip regulator via the V
DD(REG)(3V3)
pins after entering Deep
Power-down mode.Power to the on-chip regulator must be restored before device
operation can be restarted.
Wake-up from Deep Power-down mode will occur when an external reset signal is
applied, or the RTC interrupt is enabled and an RTC interrupt is generated.
8.5 Peripheral power control
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. This is
detailed in the description of the PCONP register.
8.6 Register description
The Power Control function uses registers shown in
. More detailed
descriptions follow.
[1]
Reset Value reflects the data stored in used bits only. It does not include reserved bits content.
Table 43.
Power Control registers
Name
Description
Access Reset
value
Address
PCON
Power Control Register. This register
contains control bits that enable some
reduced power operating modes of the
LPC17xx. See
R/W
0x00
0x400F 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
0x400F C0C4