p89lpc9401 NXP Semiconductors, p89lpc9401 Datasheet - Page 22

• Manufacturer Part Number: p89lpc9401
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 8 Kb 3 V Byte-erasable Flash With 32 Segment X 4 Lcd Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
P89LPC9401_1
Preliminary data sheet
7.13.1.1 Quasi-bidirectional output configuration
7.13.1.2 Open-drain output configuration
7.13.1.3 Input-only configuration
7.13.1.4 Push-pull output configuration
7.13.2 Port 0 analog functions
Quasi-bidirectional output type can be used as both an input and output without the need
to reconfigure the port. This is possible because when the port outputs a logic HIGH, it is
weakly driven, allowing an external device to pull the pin LOW. When the pin is driven
LOW, it is driven strongly and able to sink a fairly large current. These features are
somewhat similar to an open-drain output except that there are three pull-up transistors in
the quasi-bidirectional output that serve different purposes.
The P89LPC9401 is a 3 V device, but the pins are 5 V-tolerant. In quasi-bidirectional
mode, if a user applies 5 V on the pin, there will be a current flowing from the pin to V
causing extra power consumption. Therefore, applying 5 V in quasi-bidirectional mode is
discouraged.
A quasi-bidirectional port pin has a Schmitt trigger input that also has a glitch suppression
circuit.
The open-drain output configuration turns off all pull-ups and only drives the pull-down
transistor of the port driver when the port latch contains a logic 0. To be used as a logic
output, a port configured in this manner must have an external pull-up, typically a resistor
tied to V
An open-drain port pin has a Schmitt trigger input that also has a glitch suppression
circuit.
The input-only port configuration has no output drivers. It is a Schmitt trigger input that
also has a glitch suppression circuit.
The push-pull output configuration has the same pull-down structure as both the
open-drain and the quasi-bidirectional output modes, but provides a continuous strong
pull-up when the port latch contains a logic 1. The push-pull mode may be used when
more source current is needed from a port output. A push-pull port pin has a Schmitt
trigger input that also has a glitch suppression circuit.
The P89LPC9401 incorporates two analog comparators. In order to give the best analog
function performance and to minimize power consumption, pins that are being used for
analog functions must have the digital outputs and digital inputs disabled.
Digital outputs are disabled by putting the port output into the Input-Only
(high-impedance) mode.
Digital inputs on Port 0 may be disabled through the use of the PT0AD register, bits 1:5.
On any reset, PT0AD[1:5] defaults to logic 0s to enable digital functions.
1. P1.5 (RST) can only be an input and cannot be configured.
2. P1.2 (SCL/T0) and P1.3 (SDA/INT0) may only be configured to be either input-only or
open-drain.
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8-bit two-clock 80C51 microcontroller with 32 segment
Rev. 01 — 5 September 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
P89LPC9401
4 LCD driver
22 of 59
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