VTech Alphabert s Magic Readport User Manual download pdf (Page 45)

BM Dept., Govt. Engg. College, Gandhinagar Page 45

MOV TH1,#0FDh ;Count value for baud rate 9600

MOV SCON,#50h ;8 bit UART mode, REN enable

MOV P0,#00h ;Port P0 output port

SETB TR1 ;Start timer 1 to generated baud rate.

CHECK:

JNB RI,CHECK ; Check whether data byte is received or not

MOV P0,SBUF ; Display received data on port P0

CLR RI ; Clear RI flag

SJMP CHECK ;Repeat task

END

Program 2: Serial data reception using interrupt method:

In interrupt method, instead of checking RI flag continuously we use serial port

interrupt. When RI flag set, program will automatically jump to the location 0023h which is

vector location of serial interrupt. In this program we read port P1 continuously and display its

content on port P2.

ORG 00h

AJMP start

ORG 23h ;Location for serial interrupt

MOV P0,SBUF ; Display received data on port P0.

start: CLR RI

RETI ;Return from the ISR

MOV P1,#0ffh ;Make P1 output port

MOV P2,#00h ;Make P2 output port

MOV TMOD,#20h ;Timer 1, mode-2 ( auto reload mode)

MOV TH1,#0FDh ;Count value for baud rate 9600

MOV SCON,#50h ;8 bit UART mode, REN enable

MOV IE,#90h ; Enable serial interrupt and EA bit

SETB TR1 ;Start timer 1 to generated baud rate.

next: MOV A, P1 ; Read port P1

MOV P2,A ; Display content of port P1 on port P2.

SJMP next ;Repeat task

END

Program 3: Program at computer side:

Program for serial communication in “C” language is given here. Alternately we can use

hyper terminal or XTalk software for serial communication.

#include <dos.h>

#include <stdio.h>

#include <conio.h>

#define PORT1 0x3F8

/* Defines Serial Ports Base Address */

/* COM1 0x3F8 COM2 0x2F8 COM3 0x3E8 COM4 0x2E8 */

void main(void)

{

int c,ch;

outportb(PORT1 + 1 , 0); /* Turn off interrupts - Port1 */

outportb(PORT1 + 0 , 0x0C); /* Baud rate 9600 */

/* Set Baud rate - Divisor Latch Low Byte */

/* Default 0x03 = 38,400 BPS 0x01 = 115,200 BPS 0x02 = 57,600 BPS

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VTech Alphabert s Magic Readport User Manual Page 45

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