Thread: 8051 micro controller programming

An Application software requires an accurate 0.25 second delay function
to flash an LED. Show how you would program the C8051F020 to
generate such a delay using interrupts.

A student needs to do his homework. Show us some effort.

kk.... sory .. i have done it with timer 2 ... bt i dont know how to specify the time delay... :-)

prog:

Code:

//-- Filename : Lab3A.c
//-- This program makes the 4 green LEDs (on P5.4 to P5.7) blink (all together)
//-- Uses Timer 2 and interrupts to control the blinking (on/off) period.
//-- (Using Timer 4 is very similar to Timer 2)
//-- Uses 2 MHz internal Oscillator (default)

#include <c8051f020.h>			  // SFR declarations

//------------------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F02x
//------------------------------------------------------------------------------------

sfr16 DP     = 0x82;            // data pointer
sfr16 TMR3RL = 0x92;            // Timer3 reload value
sfr16 TMR3   = 0x94;            // Timer3 counter
sfr16 ADC0   = 0xBE;            // ADC0 data
sfr16 ADC0GT = 0xC4;            // ADC0 greater than window
sfr16 ADC0LT = 0xC6;            // ADC0 less than window
sfr16 RCAP2  = 0xCA;            // Timer2 capture/reload
sfr16 T2     = 0xCC;            // Timer2
sfr16 RCAP4  = 0xE4;            // Timer4 capture/reload
sfr16 T4     = 0xF4;            // Timer4
sfr16 DAC0   = 0xD2;            // DAC0 data
sfr16 DAC1   = 0xD5;            // DAC1 data

enum {NORMAL, HIGH};
unsigned char count;

//------------------------------------------------------------------------------------
// Function PROTOTYPES
//------------------------------------------------------------------------------------
void init_Port(void);         		// general system initialization
void Init_Timer2(unsigned int counts);
void Timer2_ISR(void);		//-- ISR for Timer 2

void main(void)
{
	unsigned char blink_speed = NORMAL;
	count = 0;

	EA = 0;		//-- disable global interrupts
				//-- It is a good idea to disable interrupts before all the initialisation
				//-- is complete

	//-- disable watchdog timer
	WDTCN = 0xDE;
	WDTCN = 0xAD;

	init_Port();

	if (blink_speed == NORMAL)
		Init_Timer2(7203);	//-- Initialise Timer2 to generate interrupts every 350ms
	else	//-- blink_speed is HIGH
		Init_Timer2(53036);	//-- Initialise Timer2 to generate interrupts every 75ms

	P5 = P5 & 0xFF;			//-- turn ON the four LEDs

	EA = 1;		//-- enable global interrupts

	while (1);	//-- go on forever (endless loop)

}

void init_Port(void)
{
	//----- Configure the XBRn Registers
	XBR0 = 0x00;
	XBR1 = 0x00;
	XBR2 = 0x40;					  // Enable the crossbar, weak pullups enabled
	// To disable weak pull-ups, XBR2 = 0xC0;

	//------ Port configuration (0 = Open Drain Output, 1 = Push Pull Output)
	P0MDOUT = 0x00;				  // Output configuration for P0 
	P1MDOUT = 0x00;				  // Output configuration for P1
	P2MDOUT = 0x00;				  // Output configuration for P2 
	P3MDOUT = 0x00;				  // Output configuration for P3 

	//-- Port 7-4 I/O Lines
	P74OUT = 0x08;				  // Output configuration for P4-7
								  // (P5[7:4] Push Pull) - 4 LEDs
								  // (P5[3:0] Open Drain) - 4 Push-Button Switches (input)
								  // (P4 Open Drain) - 8 DIP Switches (input)

	//-- Write a logic 1 to those pins which are to be used for input
	P5 |= 0x0F;
	P4 = 0xFF;
}

//-- Configure Timer2 to auto-reload and generate an interrupt at interval
//-- specified by <counts> using SYSCLK/12 as its time base.
void Init_Timer2 (unsigned int counts)
{
	CKCON = 0x00;		//-- Define clock (T2M). Timer 2 uses system clock DIV BY 12
//	CKCON |= 0x20;		//-- if you want to use system clock
	T2CON = 0x00;		//-- T2CON.1 = 0 -->T2 set for Timer function (C/T2) i.e.
						//--				incremented by clock defined by T2M
						//-- T2CON.0 = 0 -->Allow Auto-reload on Timer2 overflow (CP/RL2)
						//-- T2CON.3 = 0 -->High-to-Low transitions on T2EX ignored (EXEN2)
						//-- T2CON.2 = 0 -->Disable Timer2

	RCAP2 = counts;	//-- Init reload values in the Capture registers
	T2 = 0xFFFF;		//-- count register set to reload immediately when the first clock occurs
	IE |= 0x20;			//-- IE.5, Enable Timer 2 interrupts (ET2)
	T2CON |= 0x04;		//-- start Timer2 by setting TR2 (T2CON.2) to 1
}

//-- Interrupt Service Routine
//-- This routine changes the state of the LEDs whenever Timer2 overflows.
void Timer2_ISR (void) interrupt 5
{
	T2CON &= ~(0x80);		//-- clear TF2. This is not automatically cleared, must be
							//-- done by software upon overflow.

	P5 = P5 ^ 0xF0;			//-- toggle the four LEDs using EX-OR with '1'
}