P89LPC920FDH PHILIPS [NXP Semiconductors], P89LPC920FDH Datasheet - Page 20

• Manufacturer Part Number: P89LPC920FDH
• Description: 8-bit microcontrollers with two-clock 80C51 core 2 kB/4 kB/8 kB 3 V low-power Flash with 256-byte data RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 12285
Product data
8.12.7 Additional port features
8.13.1 Brownout detection
8.13.2 Power-on detection
8.13 Power monitoring functions
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 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 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 operating voltage range for V
and the brownout condition occurs when V
V
above V
2.4 V to 3.6 V. If the P89LPC920/921/922 device is to 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.
•
•
BO
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.
(see
BO
Table 8 “DC electrical
. If brownout detection is disabled, the operating voltage range for V
Rev. 06 — 21 November 2003
Table 8 “DC electrical characteristics”
characteristics”), and is negated when V
8-bit microcontrollers with two-clock 80C51 core
Table 8 “DC electrical characteristics”
P89LPC920/921/922
DD
falls below the brownout trip voltage,
DD
rise and fall times must be
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
for specifications.
DD
is 2.7 V to 3.6 V,
DD
rises
for
20 of 45
DD
is