p89lpc904 NXP Semiconductors, p89lpc904 Datasheet - Page 23

• Manufacturer Part Number: p89lpc904
• Description: 8-bit Microcontrollers With Two-clock Accelerated 80c51 Core 1 Kb 3 V Byte-erasable Flash With 8-bit A/d Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13521
Preliminary data
8.13.7 Additional port features
8.14.1 Brownout detection
8.14.2 Power-on detection
8.14 Power monitoring functions
8.15 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 P89LPC904 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
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 P89LPC904 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 P89LPC904 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.
The P89LPC904 supports three different power reduction modes. These modes are
Idle mode, Power-down mode, and total Power-down mode.
•
•
BO
After power-up all I/O pins, except P1.5, may be configured by software.
Pin P1.5 is input only.
(see
BO
Table 8 “DC electrical
. If brownout detection is disabled, the operating voltage range for V
Rev. 02 — 25 June 2004
8-bit microcontrollers with two-clock accelerated 80C51 core
Table 8 “DC electrical characteristics”
Table 8 “DC electrical characteristics”
characteristics”), and is negated when V
DD
falls below the brownout trip voltage,
DD
rise and fall times must be
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89LPC904
for specifications.
for detailed
DD
is 2.7 V to 3.6 V,
DD
rises
DD
23 of 41
is