P89LPC9211 datasheet(34/75 Pages) NXP

34 / 75 page

P89LPC92X1

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Product data sheet

Rev. 2 — 1 December 2010

34 of 75

NXP Semiconductors

P89LPC9201/9211/922A1/9241/

8-bit microcontroller with 8-bit ADC

7.17.1 Brownout detection

The brownout detect function determines if the power supply voltage drops below a

certain level. Enhanced brownout detection has 3 independent functions: BOD reset,

BOD interrupt and BOD FLASH.

BOD reset is always on except in total Power-down mode. It could not be disabled in

software. BOD interrupt may be enabled or disabled in software. BOD FLASH is always

on, except in Power-down modes and could not be disabled in software.

BOD reset and BOD interrupt, each has four trip voltage levels. BOE1 bit (UCFG1.5) and

BOE0 bit (UCFG1.3) are used as trip point configuration bits of BOD reset. BOICFG1 bit

and BOICFG0 bit in register BODCFG are used as trip point configuration bits of BOD

interrupt. BOD reset voltage should be lower than BOD interrupt trip point. BOD FLASH is

used for flash programming/erase protection and has only 1 trip voltage of 2.4 V. Please

refer to P89LPC9201/9211/922A1/9241/9251 User manual for detail configurations.

If brownout detection is enabled the brownout condition occurs when VDD falls below the

brownout trip voltage and is negated when VDD rises above the brownout trip voltage.

For correct activation of brownout detect, the VDD rise and fall times must be observed.

Please see Table 12 “Static characteristics” for specifications.

7.17.2 Power-on detection

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.

7.18 Power reduction modes

The P89LPC9201/9211/922A1/9241/9251 supports three different power reduction

modes. These modes are Idle mode, Power-down mode, and total Power-down mode.

7.18.1 Idle 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.

7.18.2 Power-down mode

The Power-down mode stops the oscillator in order to minimize power consumption. The

P89LPC9201/9211/922A1/9241/9251 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 supply voltage VDDR. This retains the RAM contents at the point where

Power-down mode was entered. SFR contents are not guaranteed after VDD has been

lowered to VDDR, therefore it is highly recommended to wake-up the processor via reset in

this case. VDD must be raised to within the operating range before the Power-down mode

is exited.

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