Philips Semiconductors

User’s Manual - Preliminary -

 

 

 

 

 

 

I/O PORTS

P89LPC901/902/903

 

 

4. I/O PORTS

 

 

The P89LPC901/902/903 has between 3 and 6 I/O pins. The exact number of I/O pins available depends on the clock and reset options chosen:

Table 4-1: Number of I/O Pins Available

 

 

 

 

Number of I/O

Clock Source

Reset Option

Pins

 

 

 

 

8-Pin Package

On-chip oscillator or watchdog

No external reset(except during power-up)

6

oscillator

External

 

pin supported

5

RST

External clock input

No external reset(except during power-up)

5

 

 

 

 

 

 

 

 

External RST pin supported

4

 

Low/medium/high speed oscillator

No external reset(except during power-up)

4

(external crystal or resonator)

 

 

 

 

 

 

 

 

External RST pin supported

3

(P89LPC901)

 

 

 

 

 

 

 

 

 

Port Configurations

All but one I/O port pin on the P89LPC901/902/903 may be configured by software to one of four types on a pin-by-pin basis, as shown in Table . These are: quasi-bidirectional (standard 80C51 port outputs), push-pull, open drain, and input-only. Two configuration registers for each port select the output type for each port pin. P1.5 (RST) can only be an input and cannot be configured.

Table 4-2: Port Output Configuration Settings

PxM1.y

PxM2.y

Port Output Mode

0

0

Quasi-bidirectional

 

 

 

0

1

Push-Pull

 

 

 

1

0

Input Only (High Impedance)

 

 

 

1

1

Open Drain

 

 

 

Quasi-Bidirectional Output Configuration

Quasi-bidirectional outputs can be used both as 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 large current. There are three pullup transistors in the quasi-bidirectional output that serve different purposes.

One of these pullups, called the "very weak" pullup, is turned on whenever the port latch for the pin contains a logic 1. This very weak pullup sources a very small current that will pull the pin high if it is left floating.

A second pullup, called the "weak" pullup, is turned on when the port latch for the pin contains a logic 1 and the pin itself is also at a logic 1 level. This pullup provides the primary source current for a quasi-bidirectional pin that is outputting a 1. If this pin is pulled low by an external device, this weak pullup turns off, and only the very weak pullup remains on. In order to pull the pin low under these conditions, the external device has to sink enough current to overpower the weak pullup and pull the port pin below its input threshold voltage.

2003 Dec 8

39

Page 38 Page 40
Page 39
Image 39
Philips P89LPC901, P89LPC903, P89LPC902 user manual Port Configurations, Quasi-Bidirectional Output Configuration, Rst
Page 38 Page 40

P89LPC903, P89LPC902, P89LPC901 specifications

The Philips P89LPC901, P89LPC902, and P89LPC903 are a series of 8-bit microcontrollers designed for embedded system applications. These models, which belong to the LPC900 series, are notable for their affordability and versatility, making them an attractive choice for both hobbyists and professional developers.

One of the core features of the P89LPC901, P89LPC902, and P89LPC903 microcontrollers is their powerful 8-bit architecture. Operating at clock speeds up to 20 MHz, they deliver efficient performance suited for a range of tasks. Each model includes a comprehensive instruction set that supports various data manipulation and arithmetic functions, enabling extensive programming capabilities.

These microcontrollers come with built-in memory, with configurations that vary among the three models. The P89LPC901 typically features 4 KB of Flash memory and 256 bytes of RAM, while the P89LPC902 and P89LPC903 offer enhanced memory options. This Flash memory allows for reprogrammability, making it easier to update and modify applications as needed.

Another significant characteristic of the LPC900 series is their integrated peripherals. These models are equipped with a variety of I/O ports, allowing for easy interfacing with other devices and components. The P89LPC901 supports up to 32 I/O pins, while the P89LPC902 and P89LPC903 provide additional features such as analog-to-digital converters (ADCs), timers, and serial communication interfaces. This broad range of peripherals empowers developers to design complex applications without needing extra hardware.

Power consumption is also a key consideration for microcontroller applications. The P89LPC901, P89LPC902, and P89LPC903 are designed with low power consumption in mind, making them ideal for battery-operated devices and energy-efficient projects. They can operate in various power modes, allowing for greater flexibility in deployment.

In terms of technology, these microcontrollers utilize advanced CMOS technology, ensuring high reliability and durability. Their design offers a robust solution for numerous applications, including consumer electronics, industrial controls, and automation systems.

In summary, the Philips P89LPC901, P89LPC902, and P89LPC903 microcontrollers present an attractive combination of performance, integrated peripherals, low power consumption, and versatility. Their features cater to a wide array of applications, keeping them relevant in a rapidly evolving technology landscape. For hobbyists and professionals alike, these microcontrollers represent a reliable foundation for embedded system development.
Top Page Image Contents