Philips Semiconductors

User’s Manual - Preliminary -

 

 

 

 

 

 

I/O PORTS

P89LPC901/902/903

 

The third pullup is referred to as the "strong" pullup. This pullup is used to speed up low-to-high transitions on a quasi-bidirectional port pin when the port latch changes from a logic 0 to a logic 1. When this occurs, the strong pullup turns on for two CPU clocks quickly pulling the port pin high .

The quasi-bidirectional port configuration is shown in Figure 4-1.

Although the P89LPC901/902/903 is a 3V device the pins are 5V-tolerant (except for XTAL1 and XTAL2). If 5V is applied to a pin configured in quasi-bidirectional mode, there will be a current flowing from the pin to VDD causing extra power consumption. Therefore, applying 5V to pins configured in quasi-bidirectional mode is discouraged.

A quasi-bidirectional port pin has a Schmitt-triggered input that also has a glitch suppression circuit. (Please refer to the P89LPC901/902/903 datasheet, AC Characteristics for glitch filter specifications)

VDD

VDD

VDD

port latch data

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2 CPU

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

clock delay

 

 

 

 

 

 

 

 

 

strong

 

 

 

 

 

very

 

 

 

 

 

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input data

glitch rejection

Figure 4-1: Quasi-Bidirectional Output

Open Drain Output Configuration

The open drain output configuration turns off all pullups and only drives the pulldown transistor of the port pin 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 pullup, typically a resistor tied to VDD. The pulldown for this mode is the same as for the quasi-bidirectional mode.

The open drain port configuration is shown in Figure 4-2.

An open drain port pin has a Schmitt-triggered input that also has a glitch suppression circuit .(Please refer to the P89LPC901/ 902/903 datasheet, AC Characteristics for glitch filter specifications).

port latch data

input data

port

pin

glitch rejection

Figure 4-2: Open Drain Output

2003 Dec 8

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Philips P89LPC903, P89LPC901, P89LPC902 user manual Open Drain Output Configuration, Quasi-Bidirectional Output
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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.
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