P89LPC970FDH datasheet(26/66 Pages) NXP

26 / 66 page

P89LPC97X_2

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Product data sheet

Rev. 02 — 27 April 2010

26 of 66

NXP Semiconductors

P89LPC970/971/972

8-bit microcontroller with accelerated two-clock 80C51 core

7.16.1.3

Input-only configuration

The input-only port configuration has no output drivers. It is a Schmitt trigger input that

also has a glitch suppression circuit.

7.16.1.4

Push-pull output configuration

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 triggered input that also has a glitch suppression circuit. The P89LPC970/971/972

device has high current source on eight pins in push-pull mode. See Table 10 “Limiting

values”.

7.16.2 Port 0 analog functions

The P89LPC970/971/972 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.

7.16.3 Additional port features

After power-up, all pins are in input-only mode. Please note that this is different from

the LPC76x series of devices.

• 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 are configurable for either input-only or

open-drain.

Every output on the P89LPC970/971/972 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 Table 11 “Static characteristics” for 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.

7.16.4 Pin remap

This feature allows the functions of UART/I2C/SPI to be remapped to other pins.

Configuration register controls the multiplexers to allow connection between the pins and

the on chip peripherals. See Table 8 “SPI/I2C/UART pin remap”.

UART/I2C/SPI, each has two options of pin configuration: primary pin map and alternative

pin map. After reset, UART/I2C/SPI chooses the primary pin map as default. User can

adjust to the alternative pin map through configuring PINCON register according to the

application.

Please refer to P89LPC970/971/972 User manual for detail configurations.

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