Ian Cameron wrote:
>
> > I am working on two PIC16C63 projects. Both involve serial communication
> > with other (Dallas) controller. Reception is interrupt driven (just one
> > byte to receive). Both interrupt service routines are almost identical
> > (interrupt enables, reception enables etc.) Nevertheless, while in one
> > project communication is flawless, in other project reception stops at
> > certain point and never happens again until program restarts (the rest
> > of the program still working just fine).
> > Will appreciate any advice.
>
> Is it possible that you are getting receiver overruns ?  I had this
> problem on a 16C63 where it would appear to lock up and would not
> receive any more characters.
>
> The way I did it was to check RCSTA:FERR.  If an overrun had
> ocurred I read RCREG twice to empty the receive shift register, and
> then reset the receiver by clearing RCSTA:CREN, and then setting it
> again.
>
> Hope this helps.
>
> Cheers, Ian.

Well, you are right. I've checked and I do get an overrun error (no
framing errors though).
I am trying to do everything to correct the problem (read buffer twice,
reset the receiver, check one more time for data in a buffer), but
anyway it finally ends up with overrun error and no reception. Will
really appreciate if anybody can point to me where the problem is. Here
is my interrupt routine (no other interrupts are enabled):
;===========================
RECEIVE_ROUTINE
        clrwdt
;
        btfss   STATUS,RP0      ;Check bank
        goto    NOTSET
        bcf     STATUS,RP0
        call    DEVELOP_MESSAGE
        bsf     STATUS,RP0      ;Restore bank
        retfie
NOTSET
        call    INTMAIN
        bcf     STATUS,RP0      ;Restore bank
        retfie
;-------------
DEVELOP_MESSAGE
        movwf   TEMP_W          ;Save context
        swapf   STATUS,W
        movwf   TEMP_STATUS
;
        bank1
        bcf     PIE1,RCIE       ;for any reason - disable serial interrupt
;
CHECK_OVERRUN
        bank0
        btfss   RCSTA,  OERR    ;If overrun - read twice, reset and get out
        goto    READ_SERIAL_NORMAL
CORRECT_SERIAL
        movf    RCREG,W
        movf    RCREG,W
        bcf     RCSTA,CREN
        bsf     RCSTA,CREN
        goto    OUT_SER
READ_SERIAL_NORMAL
        bank0
        movf    RCREG,0         ;read serial buffer
        movwf   TEMPREBUF       ;store in temp location
;
....... MESSAGE DEVELOPMENT
;
OUT_SERIAL1
        bank0
        btfsc   PIR1,RCIF       ;If buffer is not empty - read again
        goto    READ_SERIAL_NORMAL
OUT_SER
        bank1
        bsf     PIE1,RCIE       ;enable serial interrupt
        bank0
;
        swapf   TEMP_W,F        ;Restore context
        swapf   TEMP_STATUS,W
        movwf   STATUS
        swapf   TEMP_W,W
;
        return
;====================================
(bank0 and bank1 are macros defining RP0)

It seems pretty straightforward.
Is there anything I've overlooked? Is there any way around?

Gennady Palitsky
gennadyp@mainlink.net