Overview

In this course we mainly learned about:

• Structure of Microcomputer
• I/O Interface and Interrupt Mechanism
• Programmable Digital Interface circuit: Timer 8253, Parallel Interface 8255 and Interrupt Controller 8259.

一、Structure of Microcomputer

The Structure of microcomputer is just like the structure of normal computer.

See it in principles of computer composition.

二、I/O Interface and Interrupt

1) I/P Interface

I/O Interface is the bridge between CPU and external equipments.

It solves the problem like speed mismatch and signal drive.

The structure of I/O Interface:

2) Interrupt

Sometimes during the working of CPU, some random events will occur. Then the CPU has to stop to handle these events.

We call these unexpectable events interrupts. There are many types of interrupts. Some of them can be ignored and some of them not.

The process of an interrupt os as follows:

In order to quickly find the corresponding interrupt handler, we store the entry address of the handler in the interrupt vector table

三、Programmable Digital Interface Circuit

We can use assembly language to control these there chips.

1) Timer 8253

8253 can realize counting and timing.

The working mode is subtraction counting, when the count value becomes 0, the control signal we want is output.

2) Parallel Interface 8255

8255 is mainly used for data input and output.

It contains 3 independent parallel I/O ports, each of them can be used as an input/output port.

3) Interrupt Controller 8259

We can use 8259 to control interrupts from external devices and selectively pass the interrupts to the CPU.