Скачать или смотреть Microcontroller PIC16F887 Video 39 How To Enable Timer 1 Interrupt

Interrupt

A single microcontroller can serve several devices. There are two methods by which devices receive service from the microcontroller: interrupts or polling. In polling, the microcontroller continuously monitors the status of a given device; when the status condition is met, it performs the serviced. After that it moves on to monitor the next device until each one is serviced. In the interrupt method, whenever any device needs the microcontroller’s service, the device notifies it by sending an interrupt signal. Upon receiving an interrupt signal, the microcontroller stops whatever it is doing and serves the device. The program associated with the interrupt is called the interrupt service routine (ISR).

The first thing the microcontroller does when an interrupt request arrives is to execute the current instruction and then stops the regular program execution. As a result, the current program memory address is automatically pushed onto the stack and the default address (predefined by the manufacturer) is written to the program counter. The location from where the program proceeds with execution is called an interrupt vector.

Enabling Timer-1 Interrupt

All interrupts are disabled by default. The interrupts must be enable by software in order for the microcontroller to respond to them. The INTCON register is responsible for enabling and disabling the interrupts.

Project Description

The 7 segments display are connected to PORTC of a PIC16F887 microcontroller, and the microcontroller operated with a 4MHz crystal. Current limiting resistors are used on each segment of the display. Each digit is enabled using a BC108-type transistor connected to pins RD6 and RD7 of the microcontroller. A segment is turned on when a logic 1 is applied to the base of the corresponding segment transistor.

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