INTEL 8259 Datasheet

The INTEL 8259 Programmable Interrupt Controller (PIC) is a vital component in many x86-based computer systems. Understanding its function and configuration is key to comprehending how hardware interrupts are managed. This article explores the details within the INTEL 8259 Datasheet, offering insights into its operation and significance.

Delving into the INTEL 8259 Datasheet and Its Significance

The INTEL 8259 Datasheet is more than just a technical document; it’s the definitive guide to understanding the 8259 PIC’s architecture, functionality, and programming. It outlines the chip’s pinout, its various operating modes, and the command words necessary for configuring and controlling it. These command words, sent through the microprocessor, allow the programmer to determine which interrupt requests (IRQs) are enabled, their priority, and how they are handled. The datasheet is crucial for any developer working with systems that rely on the 8259 to manage hardware interrupts efficiently.

The 8259 acts as a traffic controller for interrupt requests. Imagine a busy intersection where different roads (hardware devices) need to signal for passage (CPU attention). The 8259 prioritizes these requests and passes the highest-priority one to the CPU. This allows the CPU to respond to critical events, such as a disk drive needing attention or a network card receiving data, without constantly polling each device. Here’s a simplified view of its core functionality:

• Receives interrupt requests (IRQs) from multiple devices.
• Prioritizes these requests based on a configurable priority scheme.
• Sends an interrupt request to the CPU when a high-priority interrupt occurs.
• Provides information about the interrupting device to the CPU.

To appreciate the datasheet’s value, consider a few ways the 8259 is used. In early PC systems, it managed interrupts from devices like the keyboard, serial ports, and floppy disk controller. Modern systems often use Advanced Programmable Interrupt Controllers (APICs), but understanding the 8259 provides a strong foundation for grasping interrupt handling in general. The datasheet explains exactly how to configure the 8259 to cascade, enabling multiple 8259 chips to handle more than eight interrupt lines. Here’s a comparison of some modes:

For those looking to truly understand the intricacies of interrupt handling within older x86 systems, consult the official INTEL 8259 Datasheet. It provides the necessary detailed explanations to master this fundamental component.