PIC18F BTFSS, BTFSC

[davorin]

It is a while though since I last did some PIC assembly....but this one is driving me nuts the whole afternoon (o;

After reset I poll an input for a time pulse from an external device....so a combination of btfss/btfsc is the solution:

Code: [Select]

Pulse_1:
    BTFSC   PORTA, 4
    GOTO    Pulse_1

    CALL    Wait_0
Pulse_2:
    BTFSS   PORTA, 4
    GOTO    Pulse_2

    CALL    Wait_1
Pulse_3:
    BTFSC   PORTA, 4
    GOTO    Pulse_3

So this one works...but not always...sometimes hangs before "Pulse_3"...

When I try the other way around:

Code: [Select]

Pulse_1:
    BTFSS   PORTA, 4
    GOTO    Pulse_1

    CALL    Wait_0
Pulse_2:
    BTFSC   PORTA, 4
    GOTO    Pulse_2

    CALL    Wait_1
Pulse_3:
    BTFSS   PORTA, 4
    GOTO    Pulse_3

..it always hangs before "Pulse_3"....the "CALL Wait_1" and "CALL Wait_2" are just subroutines displaying LED debugging information...

Is there something special about the PIC18F4550?

Think I have configured the PORTA correctly...

Code: [Select]

    MOVLW   0Fh
    MOVWF   ADCON1
    MOVLW   7
    MOVWF   CMCON
    MOVLW   h'ff'
    MOVWF   TRISA


[davorin]

Stupid me (o;

Of course btfsc/btfss continues with an external 1Hz pulse (o;

Just realized that the GPS module already sends data to the UART, causing to overrun....
therefore a new character received was never detected...so it just hanged...

Seem clearing bit CREN in RXSTA seems to solve the problem....