Hi!

I'm having a problem with serial overrun errors, and I can't
see how.  I'm hoping someone can give me a clue.

I'm using HiTech PICC, version 8.02 with a PIC16F877 at
18.43Mhz.

I have 3 interrupts that can occur, one is a periodic
TMR1 interrupt at 2Khz, one is a TX interrupt (very
occasional), and a RX interrupt (say about about 60 chars
per second, timed sporaticly), with TX and RX at 115Kbaud
(so about 1ms per character).

Originally, my (simplified) interrupt code looked like this:

interrupt void isr()
   {
   if (TMR1IF)
      { /* fairly long processing, but well under 500us */ }
   if (TXIF)
      { /* TXIF code, seems to work */ }
   while (RCIF)
      {
      if (RCSTA & 0x06)  /* if OERR or FERR */
         { /* error processing */ }
      else
         txbuf[txbufptr++] = RCREG;
      }
   }

However, I was getting overrun errors.  No clue as to how.
So, I changed my (simplified) interrupt code to:

interrupt void isr()
   {
   if (TMR1IF)
      { /* fairly long processing, but well under 500us */ }
   if (TXIF)
      { /* TXIF code, seems to work */ }
   while ((RCIF) || (RCSTA & 0x06))
      {
      if (RCSTA & 0x06)  /* if OERR or FERR */
         { /* error processing */ }
      else
         txbuf[txbufptr++] = RCREG;
      }
   }

Yet, somehow, I'm still getting overrun errors.

I've verified that I'm getting RCIF interrupts indepedent
of TMR1IF interrupts.

Clues?

Thanks!
   Bill

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