Embedded Systems Design Europe - February 2008 - (Page 13)

feature High-end concepts typically aren’t applied to an 8-bit MCU. But don’t rule them out just yet. The basics of embedded multitasking on a BY GAMAL ALI LABIB A pplying multitasking to an embedded system based on a PIC microcontroller may look appealing. It permits full use of the PIC resources by serving more than one task at a time rather than staying idle waiting for an external event to occur and reacting accordingly from within an application. However, multitasking can turn applications into memory-hungry monsters that barely ﬁt in your PIC. Task reentrancy is one approach that tackles expanded memory tasks, especially in small to medium PICs. In this, the ﬁrst part one of a three part series about reentrant multitasking and how you can realize it with two working examples of a Microchip’s PICmicro MCU, I begin with an introduction to multitasking. In part two and three, available on www.embedded.com, I’ll get more into the meat of multitasking on the PIC. Embedded multitasking is not new. It goes back some 30 years. The Intel 8080, Zilog Z80, and Motorola 68000 were popular microcontrollers 30 years ago. Interestingly, they were very similar in processing capabilities to many of today’s microcontrollers. Those ancient devices had multiple general-purpose and index registers that could perform arithmetic and logic operations, and supported vectored interrupts and I/O ports. They had data buses with widths up to 16 bits, and address buses up to 24-bits wide. They also had large and powerful instruction sets that gave way to efﬁcient programming and ran at moderate speeds of around 10 MHz. What’s changed over the years is that today, that same processor is packaged with RAM and EPROM. Adding analogto-digital modules and EEPROM gives us today’s “microcontrollers.” PIC www.embedded.com/europe | embedded systems design europe | JANUARY – FEBRUARY 2008 13 013-014-016-017_ESDE.indd 13 7/02/08 11:38:21 http://www.embedded.com/europe

Table of Contents Feed for the Digital Edition of Embedded Systems Design Europe - February 2008

Embedded Systems Design Europe - February 2008 Contents ARTEMIS and ENIAC Get Parlimentary Approval Product Teardown Videos Come On Screen Esterel and Abslnt Integrate Products Microsoft Opens Windows to Networked Embedded Applications Trango Embeds Virtualization Tool in Cavium's Multicore CPUs MindTree - ADI Develop Security DVR Platform NXP Extends Deal with ARM to Cover MCUs Automotive and Embedded to Dominate DATE 08 ZigBee Spec Gets Smart On Energy Updated Card Spec Provides for Power-On Boot The Basics of Embedded Multitasking On a PIC Cover Feature: The Art of FPGA Construction Is Symmetric Multiprocessing For You? Accelerating MATLAB Using MEX-Files ARM Provides the Microcontroller Solution Embedded World Advertising Contracts

Embedded Systems Design Europe - February 2008

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