Hello Everybody,

I've got a program, that should when it's finished receive a character in
the range A-G from the UART, and depending on the character received perform
an AD Conversion of one of the pins, and transfer the result back to a PC

now I've got the Serial Input Working, and the A/D Conversion, and (some
form of transmission back)., but I think theres a problem in my logic to
find out what character was being received.

I thought that if I took the letter that received (the hex equilanant off
anyway) and then checking the set/clear status of the Z bit, then I could
find out which letter was received, ie. H'42' - H'42' would equal Z bit set.
But that doesn't seem to be happening, can anybody suggest a problem with
that, either logically (ie I'm being stupid) or from the code below.

Please Help.
Andrew.



loop
     call               ser_in                  ; Call ser_in,
     call               doconverstion           ; when finished in ser_in
goto transmit w
     goto       loop                    ; when finished transmitted, start
ago.

ser_in
        btfsc   rcsta,oerr              ; does rcsta indicate an overflow
error
        goto    overerror               ; if so goto overerr
        btfsc   rcsta,ferr              ; does rcsta indicate an frameing
error
        goto    frameerror              ; if so goto frameing error.

uart_ready

        btfss   pir1,rcif               ; Check If Data Received.
        goto    ser_in          ; If Not goback and recheck.

uart_gotit
        bcf     intcon,gie              ; Clear This Pin
        btfsc intcon,gie                ; Check If Cleared.
        goto    uart_gotit              ; If Not Clear reset.

        movf    rcreg,w                 ; recover UART data
        bsf     intcon,gie              ; reanable interrupts
        movwf   rx_data         ; save for later

        return

overerror
                                        ; This Would Be Called if the UART
                                        ; Subsystem went into a failure

        bcf     rcsta,cren              ; recover from the error
        movf    rcreg,w                 ; Flush The Input Buffer
        movf    rcreg,w
        movf    rcreg,w                 ; As Its Three Deep it will be fine
now
        bsf     rcsta,cren              ; turn the cren back on.
        bcf     PORTB,7                 ; Turn On the LEDS So That A Problem
Is Indicated
        bcf     PORTB,5
        bsf     PORTB,6

        movf    'Z',txreg               ; Here We Transmit to z to the HOST
so that
        movf    'Z',txreg               ; if these are received then the
host knows
                                        ; that it needs to resend the
command.

        goto    ser_in

frameerror

        bcf     rcsta,cren              ; recover from the error
        movf    rcreg,w                 ; Flush The Input Buffer
        movf    rcreg,w
        movf    rcreg,w                 ; As Its Three Deep it will be fine
now
        bsf     rcsta,cren              ; turn the cren back on.
        bcf     PORTB,7                 ; Turn On the LEDS So That A Problem
Is Indicated
        bsf     PORTB,5
        bcf     PORTB,6

        movf    'Z',txreg               ; Here We Transmit to z to the HOST
so that
        movf    'Z',txreg               ; if these are received then the
host knows
                                        ; that it needs to resend the
command.

        goto    ser_in

doconverstion

        bcf     pir1,rcif               ; Here We Clear The Received
Characters Flag,
                                        ; Only because we have to do it
sometime, and
                                        ; to get this far we have to have
received a char.

        movf    rcreg,w                 ; move the received char into the w
register

        subwf   'A',w                   ; subtract the char received from
the contents
                                        ; if we received a 'A' zero flag of
the status
                                        ; register. If we didn;t then it
should have skipped

        btfsc   status,Z
        call    do_A_Converstion

        movf    rx_data,w
        subwf   'B',w                   ; did we receive a b
        btfsc   status,Z
        call    do_B_Converstion
        bcf     status,z
        goto ser_in

do_A_Converstion

        movf    rcreg,txreg

        return

do_B_Converstion

        movf    rcreg,txreg

        return

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