lpc2377 NXP Semiconductors, lpc2377 Datasheet - Page 32

• Manufacturer Part Number: lpc2377
• Description: Single-chip 16-bit/32-bit Microcontroller; 512 Kb ?ash With Isp/iap, Ethernet, Usb 2.0, Can, And 10-bit Adc/dac
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2377_78_4
Product data sheet
7.25.4.4 Power domains
7.26.1 Reset
7.26 System control
On the wake-up of power-down mode, if the IRC was used before entering power-down
mode, it will take IRC 60 s to start-up. After this 4 IRC cycles will expire before the code
execution can then be resumed if the code was running from SRAM. In the meantime, the
flash wake-up timer then counts 4 MHz IRC clock cycles to make the 100 s flash start-up
time. When it times out, access to the flash will be allowed. The customers need to
reconfigure the PLL and clock dividers accordingly.
The LPC2377/78 provides two independent power domains that allow the bulk of the
device to have power removed while maintaining operation of the RTC and the battery
RAM.
On the LPC2377/78, I/O pads are powered by the 3.3 V (V
V
the CPU and most of the peripherals.
Depending on the LPC2377/78 application, a design can use two power options to
manage power consumption.
The first option assumes that power consumption is not a concern and the design ties the
V
supply for both pads, the CPU, and peripherals. While this solution is simple, it does not
support powering down the I/O pad ring “on the fly” while keeping the CPU and
peripherals alive.
The second option uses two power supplies; a 3.3 V supply for the I/O pads (V
a dedicated 3.3 V supply for the CPU (V
converter powered independently from the I/O pad ring enables shutting down of the I/O
pad power supply “on the fly”, while the CPU and peripherals stay active.
The VBAT pin supplies power only to the RTC and the battery RAM. These two functions
require a minimum of power to operate, which can be supplied by an external battery.
When the CPU and the rest of chip functions are stopped and power removed, the RTC
can supply an alarm output that may be used by external hardware to restore chip power
and resume operation.
Reset has four sources on the LPC2377/78: the RESET pin, the Watchdog reset,
power-on reset, and the BrownOut Detection (BOD) circuit. The RESET pin is a Schmitt
trigger input pin. Assertion of chip Reset by any source, once the operating voltage attains
a usable level, starts the Wake-up timer (see description in
timer”), causing reset to remain asserted until the external Reset is de-asserted, the
oscillator is running, a fixed number of clocks have passed, and the flash controller has
completed its initialization.
When the internal Reset is removed, the processor begins executing at address 0, which
is initially the Reset vector mapped from the Boot Block. At that point, all of the processor
and peripheral registers have been initialized to predetermined values.
DD(DCDC)(3V3)
DD(3V3)
and V
pin powers the on-chip DC-to-DC converter which in turn provides power to
DD(DCDC)(3V3)
Rev. 04 — 19 November 2008
pins together. This approach requires only one 3.3 V power
DD(DCDC)(3V3)
Single-chip 16-bit/32-bit microcontroller
). Having the on-chip DC-to-DC
DD(3V3)
Section 7.25.3 “Wake-up
LPC2377/78
) pins, while the
© NXP B.V. 2008. All rights reserved.
DD(3V3)
32 of 55
) and