Code:
list p=16F84A
#include<P16F84A.INC>
__CONFIG _PWRTE_ON & _WDT_OFF & _XT_OSC
errorlevel -302
;******************************************************************
;* Variablen *
;******************************************************************
x_start Equ 0x20
x_data1 Equ 0x21
data1 Equ 0x22
x_bytes Equ 0x23
x_bit Equ 0x24
x_onetime Equ 0x25
cycl_1 Equ 0x26
cycl_2 Equ 0x27
cnt Equ 0x28
cnt1 Equ 0x29
;******************************************************************
;* Programmstart *
;******************************************************************
org 0x00
clrf PCLATH
clrf STATUS
clrf INTCON
goto INIT
org 0x04
goto INT_RT
;******************************************************************
;* Initialisierung *
;******************************************************************
INIT
bsf STATUS, RP0
movlw b'00000001'
movwf TRISB
movlw .0
movwf TRISA
movlw b'00000111'
movwf OPTION_REG
bcf STATUS, RP0
movlw b'10110000'
movwf INTCON
clrf PORTB
clrf x_start
clrf data1
clrf x_onetime
org 0x20
sl
sleep
goto $-1
;*****************************************************************
;* Interrupt Routine *
;*****************************************************************
INT_RT
btfss x_start, 0 ; got header already?
goto INT_naglowek ; NO
goto INT_bity ; YES --> get bits
;*****************************************************************
;* detect header *
;*****************************************************************
INT_naglowek ; get header
movlw .6 ; set counter for data1
movwf x_data1 ;
bsf STATUS, RP0
movlw b'10000010' ; Prescaler 1.795ms (2.4)
movwf OPTION_REG ; for header!
bcf STATUS, RP0
bcf INTCON, T0IF
movlw .34 ; loading TMR0 to count 1.8ms
movwf TMR0
btfss INTCON, T0IF ; TMR0 overflowed??
goto $-1 ; t < t < 3t
btfsc PORTB, 0 ; YES.. if RB0=0 got header
goto fehler ; header detection failed
bsf x_start, 0 ; marking that header already detected
bcf INTCON, T0IF ;
bcf INTCON, INTF ; Clearing interrupt flags
retfie ; sleep and wait for 1st bit
;*******************************************************************
; detect bits *
;*******************************************************************
INT_bity ; Initialization due to bit detection
bsf PORTB, 2 ; debug LED
; btfsc x_onetime, 0
; goto fehler
bsf STATUS, RP0
movlw b'00000001' ; Prescaler TMR0 0.8ms
movwf OPTION_REG
bcf STATUS, RP0
bcf INTCON, T0IF
movlw .35
movwf TMR0
btfss INTCON, T0IF ; TMR0 overflowed??
goto $-1 ; 1t < t < 2t
btfss PORTB, 0 ; if after 0.903ms RB=1
goto sv_one ; one was detected, store it !!
goto sv_zero ; zero was detected, store it !!
;*******************************************************************
;* speichere 0 in data1 || store a zero in data1 *
;*******************************************************************
sv_zero
btfsc x_data1, 7 ; data1 full ??
goto got_it ; YES -> continue with data2 !!
bcf STATUS, C ; NO --> move zero in C !!
rrf data1, F ; move C in data1.
decf x_data1, F ; in order to detect if data1 is full.
bcf INTCON, T0IF ;
bcf INTCON, INTF ; Clearing interrupt flags.
retfie ; sleep and wait for NEXT bit !!
;******************************************************************
;* speichere 1 in data1 || store a one in data1 *
;******************************************************************
sv_one
btfsc x_data1, 7 ; data1 full ??
goto got_it ; YES -> continue with data2 !!
bsf STATUS, C ; NO --> move one in C !!
rrf data1, F ; move C in data1.
decf x_data1, F ; in order to detect if data1 is full.
bcf INTCON, T0IF ;
bcf INTCON, INTF ; Clearing interrupt flags.
retfie ; sleep and wait for NEXT bit !!
got_it
bsf x_onetime, 0
;******************************************************************
;* send 7 bits to RS232 || 9600bds 7n1 *
;******************************************************************
movlw .7 ; sending 7 bits
movwf cycl_1
bsf PORTB, 1
call Warte_s ; 1 Stopbit (1)
bcf PORTB, 1
call Warte_s ; 1 Startbit (0)
Send_1
rlf data1, f ; Bit into C flag !!
btfsc STATUS, C
bsf PORTB, 1 ; Hi if Bit = 1
btfss STATUS, C
bcf PORTB, 1 ; Lo if Bit = 0
call Warte_s ; wait 1 bit long !!
decfsz cycl_1, f ; already sent 7 bits ??
goto Send_1 ; NO
bsf PORTB, 1 ; YES -> send stopBit
call Warte_s ; wait 1 bit long !!
; call wrt ; loop (at the end)
goto fehler
Warte_s
movlw .16 ; 9600 Bps / 4 MHz
movwf cycl_2
Warte1
nop
nop
nop
decfsz cycl_2, 1
goto Warte1
return
fehler
bcf PORTB, 2 ; debug LED
bcf INTCON, T0IF ;
bcf INTCON, INTF ; Clearing interrupt flags.
retfie ; sleep and wait for header !!
;******************************************************************
;* loop *
;******************************************************************
;wrt
; movlw .255
; movwf cnt
; movwf cnt1
;wrt2
; decfsz cnt, F
; goto wrt3
; return
;
;wrt3
; decfsz cnt1, F
; goto wrt3
; goto wrt2
end
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