[51] 8051 Serial communication interrupt and delay

[shoaib88]

Hi, i am using AT89C51ED2 microcontroller to perform serial communication using interrupt 4. The main purpose of code program is send received data to hyper-terminal using interrupt 4 (serial interrupt, echo received data) while the led connected at P1^0 will continuously blink with a delay of 1 sec.

PROBLEM:
when i produce a delay using timer, serial communication doesn't work(timer-1 for serial communication and timer-0 for delay). On the other hand if i produce delay using for loop then it works. :thinker:

can you please help me,

here is my code.

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Code C - [expand]
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#include <reg51.h>
    
    char uart_data;
    int i;
    sbit led1 = P1^0;
        
    void serial_int_initialization();
    void SendKey (unsigned char Key);
    void delay (unsigned int sec);
 
    void main()
    {
        serial_int_initialization();
        
        while(1)
        {
            led1 = 0;
            delay(1);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            
            led1 = 1;
                                    
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            for (i = 0; i <20000; i++);
            
            delay(1);
        
                 } /* endless */
 
    }
 
 
    /**
     * FUNCTION_PURPOSE: serial interrupt, echo received data.
     * FUNCTION_INPUTS: P3.0(RXD) serial input
     * FUNCTION_OUTPUTS: P3.1(TXD) serial output
     */
    
    void serial_IT(void) interrupt 4 
    {
        if (RI == 1) 
        { /* if reception occur */
             RI = 0; /* clear reception flag for next reception */
             uart_data = SBUF; /* Read receive data */
             SendKey (uart_data);
             
        }
        else TI = 0; /* if emission occur */
    } /* clear emission flag for next emission*/
 
 
    void serial_int_initialization()   // Serial port initialization with timer-1 interrupt
    {
        SCON = 0x50; /* uart in mode 1 (8 bit), REN=1 */
        TMOD = TMOD | 0x20 ; /* Timer 1 in mode 2 */
//      TH1 = 0xFD; /* 9600 Bds at 11.059MHz */
//      TL1 = 0xFD; /* 9600 Bds at 11.059MHz */
        TH1 = 0xE8; /* 2400 Bds at 22.1184MHz */     // baud rate 19200bps,FD //baud rate 9600,FA
        TL1 = 0xE8; /* 2400 Bds at 22.1184MHz */
        ES = 1; /* Enable serial interrupt*/     
        EA = 1; /* Enable global interrupt */
        TR1 = 1; /* Timer 1 run */
    }
    
    
    void SendKey (unsigned char Key)
    {
        TI = 0;
        SBUF = Key;
        while (TI == 0);
    }
    
    //--------------------------- Delay Function -----------------------------
    
    void delay (unsigned int sec)                           // Timer function to produce a delay of 1 sec
    {
        unsigned int i;
        for(i=0; i<=50*sec; i++)      //when multiplied by 50 it produces a delay of 1 sec
        {
            TMOD=0x01;                //This timer produces a delay of 20ms
            TL0=0xFE;
            TH0=0x6F;
            TR0=1;
            while(TF0==0); 
            TR0=0;
            TF0=0;
        }
    }

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[milan.rajik]

TH1 will be used for baudrate generation. Use TMR0 for creating delay. Start TMR0 after initializing UART interrupt.

 

[shoaib88]

TH1 will be used for baudrate generation. Use TMR0 for creating delay. Start TMR0 after initializing UART interrupt.

Thank you for your reply milan.
yes i am already using TMR0 for delay. I after initializing UART interrupt, i tried to run TMR0 but still it is not working.
Can you please elaborate it?

- - - Updated - - -

Thank you for your reply.
Yes i am already using Timer-0 for delay.
I tried to start TMR0 after UART interrupt but it is not working. Can you please elaborate it further?

 

[milan.rajik]

Please zip and post you complete project files.

 

[Venkadesh_M]

Try using timer0 ISR.