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Rishi Vasuki

Rishi has been with Microchip Technology since 2001.  He has experience in developing portable music players and designing a wide variety of embedded applications (audio, security, motor control, power supplies and smart sensor).  His current focus includes PIC(R) XLP MCUs for eXtreme Low Power applications as well as Microchip's mTouch solutions using 8-bit PIC18 & 16-bit PIC24 MCUs.

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  • Hi,

     

    I am trying to transmit and recieve block of few bytes through USART. I am using PIC18F452 and PIC18F252 at two kits. I am programming in assembly language. Tranmission is @1200 baud and Procesoor clock @4Mhz.

     

    My problem is,

     

    I cant recieve byte unless insert a delay at transmitter. But it slows the communication. What could be the solution ?

     

    concerned code is copied here. How to speedup the communication eliminating <<Delay1>> between consecutive bytes.

     

     

    TRANS  
       bsf RCSTA,SPEN    ;Enable serial port
       bsf RCSTA,CREN    ;cont recieve mode
       bsf RCSTA,RX9    ;9'th bit recieve enable
      
       movlw 0x33  
    		;for 1200 baud
       movwf SPBRG    
       bcf TXSTA,BRGH    ;Lo spped baud select
       bsf TXSTA,TXEN    ;Transmit enable TXEN-1
       bsf TXSTA,TX9    ;9'th bit transmit enable
      

       movff CMD_T,TXREG    ;byte to transmit
       return

    ;-----------------------------

    TRAX   

       

    TX_L

        bcf TXSTA,TX9D    ;CLR bit 9

        movff PWM_D,CMD_T

        call TRANS

       

        call Delay1

      

    TX_H

        bsf TXSTA,TX9D    ;set bit 9

        movff PWM_V,CMD_T

        call TRANS

     

        return

     


    ...

    Delay1

       

        movlw    H'FF'

        movwf   Dx

    L2   

        movwf     Dy

        clrwdt

    L1    decfsz    Dy

        goto    L1

        decfsz  Dx

        goto    L2

        return

     

    ;;;; recieve iterrupt service routine is .....

     

    ISR_RX

     

        btfss RCSTA,RX9D

        goto LB

        goto HB

       

    HB     movff RCREG,FDBK_H

        goto OVER_RCV

       

    LB    movff RCREG,FDBK_L

       

    OVER_RCV       

       

        retfie

       

    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Reply

  • Hi,

     

    I am trying to transmit and recieve block of few bytes through USART. I am using PIC18F452 and PIC18F252 at two kits. I am programming in assembly language. Tranmission is @1200 baud and Procesoor clock @4Mhz.

     

    My problem is,

     

    I cant recieve byte unless insert a delay at transmitter. But it slows the communication. What could be the solution ?

     

    concerned code is copied here. How to speedup the communication eliminating <<Delay1>> between consecutive bytes.

     

     

    TRANS  
       bsf RCSTA,SPEN    ;Enable serial port
       bsf RCSTA,CREN    ;cont recieve mode
       bsf RCSTA,RX9    ;9'th bit recieve enable
      
       movlw 0x33  
    		;for 1200 baud
       movwf SPBRG    
       bcf TXSTA,BRGH    ;Lo spped baud select
       bsf TXSTA,TXEN    ;Transmit enable TXEN-1
       bsf TXSTA,TX9    ;9'th bit transmit enable
      

       movff CMD_T,TXREG    ;byte to transmit
       return

    ;-----------------------------

    TRAX   

       

    TX_L

        bcf TXSTA,TX9D    ;CLR bit 9

        movff PWM_D,CMD_T

        call TRANS

       

        call Delay1

      

    TX_H

        bsf TXSTA,TX9D    ;set bit 9

        movff PWM_V,CMD_T

        call TRANS

     

        return

     


    ...

    Delay1

       

        movlw    H'FF'

        movwf   Dx

    L2   

        movwf     Dy

        clrwdt

    L1    decfsz    Dy

        goto    L1

        decfsz  Dx

        goto    L2

        return

     

    ;;;; recieve iterrupt service routine is .....

     

    ISR_RX

     

        btfss RCSTA,RX9D

        goto LB

        goto HB

       

    HB     movff RCREG,FDBK_H

        goto OVER_RCV

       

    LB    movff RCREG,FDBK_L

       

    OVER_RCV       

       

        retfie

       

    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

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