Hello , I need to send one word with the serial port from the PIC16F877 =
on a bus . I made a program that reads in the state of a switch . When =
the switch is "one"(5V) he must send the word , when it's 'zero' he =
sends nothing .=20

My program must be seriously wrong because i get nothing out on my =
serial port .(I have always 5 V) Maybe i must make use of interrupts ?? =
I dont know . This is my program :

list p=3D16f877

#include <p16f877.inc>


__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & =
_WRT_ENABLE_ON & _CPD_OFF

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

; REGISTERS AND PORTS

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


RT equ 0x23


org 0x00

goto main

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

; MAIN

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

main



movlw d'8' ;8bits to send

movwf RT ;move '8' to register RT


bcf STATUS,RP1

bsf STATUS,RP0 ;BANK1


movlw b'00000010' ;PORTB-bit1 : Input of the switch

movwf TRISB

movlw b'11000000' ;PORTC-6/7 : Serial ports

movwf TRISC

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

; Transmit configuration

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

bsf TXSTA,BRGH ;Fast Mode

bcf TXSTA,SYNC

bcf STATUS,RP0 ;BANK0

bsf TXSTA,SPEN

bsf PIR1,TXIF=20

bsf RCSTA,SPEN ;enable asynchronous port

bsf STATUS,RP0 ;BANK1

bsf TXSTA,TXEN ;enable transmission

bsf TXSTA,TRMT ;set TRMT bit

bcf STATUS,RP0 ;BANK0



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

; TRANSMIT

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

w1

btfss PORTB,1 ;If the switch is 'zero' , stay in the loop w1

goto w1=20

call zend1 ;Switch=3D'1' , go to subroutine zend1

loop1 btfsc PORTB,1 ;Switch is still '1' , stay in loop1

goto loop1

goto w1 ;switch is zero , goto w1


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

; Zend1

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



zend1

movlw b'00100100' ;put the word in w

movwf TXREG ;transmit the word

loop2 decfsz RT,1 ;decrement 8

goto loop2

return=20

end

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