P89LPC920_921_922_9221 NXP Semiconductors, P89LPC920_921_922_9221 Datasheet - Page 21

• Manufacturer Part Number: P89LPC920_921_922_9221
• Description: The P89LPC920/921/922/9221 are single-chip microcontrollers designed forapplications demanding high-integration, low cost solutions over a wide range ofperformance requirements
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14469
Product data
8.12.7 Additional port features
8.13.1 Brownout detection
8.13.2 Power-on detection
8.13 Power monitoring functions
8.14 Power reduction modes
After power-up, all pins are in Input-Only mode. Please note that this is different
from the LPC76x series of devices.
Every output on the P89LPC920/921/922/9221 has been designed to sink typical
LED drive current. However, there is a maximum total output current for all ports
which must not be exceeded. Please refer to
detailed specifications.
All ports pins that can function as an output have slew rate controlled outputs to limit
noise generated by quickly switching output signals. The slew rate is factory-set to
approximately 10 ns rise and fall times.
The P89LPC920/921/922/9221 incorporates power monitoring functions designed to
prevent incorrect operation during initial power-up and power loss or reduction during
operation. This is accomplished with two hardware functions: Power-on Detect and
Brownout detect.
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
the brownout trip voltage, V
negated when V
operate with a power supply that 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
observed. 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 P89LPC920/921/922/9221 supports three different power reduction modes.
These modes are Idle mode, Power-down mode, and total Power-down mode.
•
•
After power-up, all I/O pins except P1.5, may be configured by software.
Pin P1.5 is input only. Pins P1.2 and P1.3 and are configurable for either input-only
or open-drain.
DD
Rev. 08 — 15 December 2004
rises above V
Table 8 “DC electrical characteristics”
BO
(see
P89LPC920/921/922/9221
8-bit microcontrollers with two-clock 80C51 core
BO
Table 8 “DC electrical
. If the P89LPC920/921/922/9221 device is to
Table 8 “DC electrical characteristics”
DD
rise and fall times must be
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
characteristics”), and is
for specifications.
DD
falls below
21 of 46
for