LPC1777 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
LPC1777
NXP Semiconductors.
'LPC1777' PDF : 120 Pages View PDF
NXP Semiconductors
LPC178x/7x
32-bit ARM Cortex-M3 microcontroller
The alternate PLL accepts an input clock frequency from the main oscillator in the range
of 10 MHz to 25 MHz only. When used as the USB clock, the input frequency is multiplied
up to a multiple of 48 MHz (192 MHz or 288 MHz as described above).
7.33.3 Wake-up timer
The LPC178x/7x begin operation at power-up and when awakened from Power-down
mode by using the 12 MHz IRC oscillator as the clock source. This allows chip operation
to resume quickly. If the main oscillator or the PLL is needed by the application, software
will need to enable these features and wait for them to stabilize before they are used as a
clock source.
When the main oscillator is initially activated, the wake-up timer allows software to ensure
that the main oscillator is fully functional before the processor uses it as a clock source
and starts to execute instructions. This is important at power on, all types of reset, and
whenever any of the aforementioned functions are turned off for any reason. Since the
oscillator and other functions are turned off during Power-down mode, any wake-up of the
processor from Power-down mode makes use of the wake-up Timer.
The wake-up timer monitors the crystal oscillator to check whether it is safe to begin code
execution. When power is applied to the chip, or when some event caused the chip to exit
Power-down mode, some time is required for the oscillator to produce a signal of sufficient
amplitude to drive the clock logic. The amount of time depends on many factors, including
the rate of VDD(3V3) ramp (in the case of power on), the type of crystal and its electrical
characteristics (if a quartz crystal is used), as well as any other external circuitry (e.g.,
capacitors), and the characteristics of the oscillator itself under the existing ambient
conditions.
7.33.4 Power control
The LPC178x/7x support a variety of power control features. There are four special
modes of processor power reduction: Sleep mode, Deep-sleep mode, Power-down mode,
and Deep power-down mode. The CPU clock rate may also be controlled as needed by
changing clock sources, reconfiguring PLL values, and/or altering the CPU clock divider
value. This allows a trade-off of power versus processing speed based on application
requirements. In addition, the peripheral power control allows shutting down the clocks to
individual on-chip peripherals, allowing fine tuning of power consumption by eliminating all
dynamic power use in any peripherals that are not required for the application. Each of the
peripherals has its own clock divider which provides even better power control.
The integrated PMU (Power Management Unit) automatically adjusts internal regulators
to minimize power consumption during Sleep, Deep-sleep, Power-down, and Deep
power-down modes.
The LPC178x/7x also implement a separate power domain to allow turning off power to
the bulk of the device while maintaining operation of the RTC and a small set of registers
for storing data during any of the power-down modes.
7.33.4.1 Sleep mode
When Sleep mode is entered, the clock to the core is stopped. Resumption from the Sleep
mode does not need any special sequence other than re-enabling the clock to the ARM
core.
LPC178X_7X
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5.5 — 26 April 2016
© NXP Semiconductors N.V. 2016. All rights reserved.
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