P89LPC938 NXP Semiconductors, P89LPC938 Datasheet - Page 26

• Manufacturer Part Number: P89LPC938
• Description: The P89LPC938 is a single-chip microcontroller, available in low cost packages, based ona high performance processor architecture that executes instructions in two to four clocks,six times the rate of standard 80C51 devices
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14051
Product data sheet
7.14.1 Brownout detection
7.14.2 Power-on detection
7.15.1 Idle mode
7.15.2 Power-down mode
7.15 Power reduction modes
The brownout detect function determines if the power supply voltage drops below a
certain level. The default operation is for a brownout detection to cause a processor reset,
however it may alternatively be configured to generate an interrupt.
Brownout detection may be enabled or disabled in software.
If brownout detection is enabled, the brownout condition occurs when V
brownout trip voltage, V
when V
can be below 2.7 V, BOE should be left in the unprogrammed state so that the device can
operate at 2.4 V, otherwise continuous brownout reset may prevent the device from
operating.
For correct activation of brownout detect, the V
Please see
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. The POF flag in the RSTSRC register is set to indicate an
initial power-up condition. The POF flag will remain set until cleared by software.
The P89LPC938 supports three different power reduction modes. These modes are Idle
mode, Power-down mode, and total Power-down mode.
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.
The Power-down mode stops the oscillator in order to minimize power consumption. The
P89LPC938 exits Power-down mode via any reset, or certain interrupts. In Power-down
mode, the power supply voltage may be reduced to the data retention voltage (V
retains the RAM contents at the point where Power-down mode was entered. SFR
contents are not guaranteed after V
recommended to wake up the processor via reset in this case. V
within the operating range before the Power-down mode is exited.
Some chip functions continue to operate and draw power during Power-down mode,
increasing the total power used during power-down. These include: brownout detect,
watchdog timer, comparators (note that comparators can be powered-down separately),
and RTC/system timer. The internal RC oscillator is disabled unless both the RC oscillator
has been selected as the system clock and the RTC is enabled.
DD
rises above V
Table 10 “DC electrical characteristics”
Rev. 01 — 25 February 2005
bo
bo
. If the P89LPC938 device is to operate with a power supply that
(see
Table 10 “DC electrical
DD
has been lowered to V
8-bit microcontroller with 10-bit A/D converter
DD
rise and fall times must be observed.
for specifications.
characteristics”), and is negated
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
DDR
DD
P89LPC938
, therefore it is highly
must be raised to
DD
falls below the
DDR
). This
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