Arizona Picdem 17 User Manual

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 2001 Microchip Technology Inc.

DS39024B-page 67

//****************************************************

//*   SWITCH.C

//****************************************************

//*   Rodger Richey

//*   Principal Applications Engineer

//*   Microchip Technology Incorporated

//****************************************************

//*   2 December 1998

//*   Compiled using MPLAB C17 C Compiler V2.20

//****************************************************

//*   This program toggles the state of the memory

//*   mapped LEDs when the corresponding memory mapped

//*   switch is pressed.

//****************************************************

//*   Uses an oscillator of 16MHz

//****************************************************

#include <p17c756.h>

#include <delays.h>

void main(void)

{

unsigned int LEDbuf;

unsigned int SWTbuf;

unsigned int TEMPbuf;

unsigned int Temp;

rom int *LEDptr;

rom int *SWTptr;

// Initialize pointers to the memory mapped device

LEDptr = (rom int *)0xfffd;

SWTptr = (rom int *)0xfffc;

// Initialize the LEDs and other variables

*LEDptr = 0x00ff;

LEDbuf = 0x00ff;

SWTbuf = 0x00ff;

while(1)

{

// Read the state of the switches

TEMPbuf = *SWTptr & 0x00ff;

// Determine what switch states have changed

Temp = TEMPbuf ^ SWTbuf;

// If a switch state has changed and the change

// was a switch press

if(Temp && TEMPbuf != 0x00ff)

{

// If need to toggle LED low

if(Temp&LEDbuf)

// Mask off desired 

LED

LEDbuf &= ~Temp;

// Else need to toggle LED high