Power-On Detection; Power Reduction Modes - Philips P89LPC938 User Manual

Philips Semiconductors
Table 26: Brownout options
BOE PMOD1/
(UCFG1.5) PMOD0
(PCON[1:0])
0 (erased) XX
1(program 11 (total
med) power-down)
≠ 11 (any mode
other than total
power-down)
[1] Cannot be used with operation above 12 MHz as this requires V

6.2 Power-on detection

The Power-On Detect has a function similar to the Brownout Detect, but is designed to
work as power initially comes up, before the power supply voltage reaches a level where
the Brownout Detect can function. The POF flag (RSTSRC.4) is set to indicate an initial
power-on condition. The POF flag will remain set until cleared by software by writing a
logic 0 to the bit. Note that if BOE (UCFG1.5) is programmed, BOF (RSTSRC.5) will be
set when POF is set. If BOE is unprogrammed, BOF is meaningless.

6.3 Power reduction modes

The P89LPC938 supports three different power reduction modes as determined by SFR
bits PCON[1:0] (see
User manual
[1]
BOPD BOI
(PCON.5) (PCON.4)
X X
X X
1 (brownout X
detect
power-down)
0 (brownout 0 (brownout
detect active) detect
generates
reset)
1 (brownout
detect
generates an
interrupt)
Table 27).
Rev. 03 — 7 June 2005
EBO EA (IEN0.7)
(IEN0.5)
X X
X X
X X
X X
1 (enable 1 (global
brownout interrupt
interrupt) enable)
0 X
X 0
of 3.0 V or above.
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UM10119
P89LPC938 User manual
Description
Brownout disabled. V
DD
operating range is 2.4 V to 3.6 V.
Brownout disabled. V
DD
operating range is 2.4 V to 3.6 V.
However, BOPD is default to
logic 0 upon power-up.
Brownout reset enabled. V
operating range is 2.7 V to 3.6 V.
Upon a brownout reset, BOF
(RSTSRC.5) will be set to
indicate the reset source. BOF
can be cleared by writing a
logic 0 to the bit.
Brownout interrupt enabled. V
operating range is 2.7 V to 3.6 V.
Upon a brownout interrupt, BOF
(RSTSRC.5) will be set. BOF can
be cleared by writing a logic 0 to
the bit.
Both brownout reset and
interrupt disabled. V operating
DD
range is 2.4 V to 3.6 V. However,
BOF (RSTSRC.5) will be set
when V falls to the Brownout
DD
Detection trip point. BOF can be
cleared by writing a logic 0 to the
bit.
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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