p87lpc778 NXP Semiconductors, p87lpc778 Datasheet - Page 43

• Manufacturer Part Number: p87lpc778
• Description: Cmos Single-chip 8-bit 80c51 Microcontroller 128-byte Data Ram, 8 Kb Otp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 12378
Product data
8.11.2 Power-on detection
8.12.1 Idle mode
8.12.2 Power-down mode
8.12 Power reduction modes
If the Brownout Detect function is not required in an application, it may be disabled,
thus saving power. Brownout Detect is disabled by setting the control bit BOD in the
AUXR1 register (AUXR1.6).
The Power-on Detect has a function similar to the Brownout Detect, but is designed to
work as power comes up initially, before the power supply voltage reaches a level
where Brownout Detect can work. When this feature is activated, the POF flag in the
PCON register is set to indicate an initial power up condition. The POF flag will
remain set until cleared by software.
The P87LPC778 supports Idle and Power-down modes of power reduction.
The Idle mode leaves peripherals running in order to allow them to activate the
processor when an interrupt is generated. Any enabled interrupt source or Reset may
terminate Idle mode. Idle mode is entered by setting the IDL bit in the PCON register
(see Tables
The Power-down mode stops the oscillator in order to absolutely minimize power
consumption. Power-down mode is entered by setting the PD bit in the PCON register
(see Tables
The processor can be made to exit Power-down mode via Reset or one of the
interrupt sources shown in
priority is higher than any interrupt currently in progress.
In Power-down mode, the power supply voltage may be reduced to the RAM
keep-alive voltage V
Power-down mode was entered. SFR contents are not guaranteed after V
been lowered to V
Reset in this case. V
Power-down mode is exited. Since the Watchdog timer has a separate oscillator, it
may reset the processor upon overflow if it is running during Power-down.
Note that if the Brownout Detect reset is enabled, the processor will be put into reset
as soon as V
as an interrupt and is enabled, it will wake up the processor from Power-down mode
when V
When the processor wakes up from Power-down mode, it will start the oscillator
immediately and begin execution when the oscillator is stable. Oscillator stability is
determined by counting 1024 CPU clocks after start-up when one of the crystal
oscillator configurations is used, or 256 clocks after start-up for the internal RC or
external clock input configurations.
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drops below the brownout voltage.
41
41
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and 42).
and 42).
drops below the brownout voltage. If Brownout Detect is configured
RAM
Rev. 01 — 31 March 2004
RAM
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, therefore it is recommended to wake up the processor via
must be raised to within the operating range before the
. This retains the RAM contents at the point where
Table
40. This will occur if the interrupt is enabled and its
CMOS single-chip 8-bit microcontroller
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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