Setting interrupt flag when a specific key has be enter

 void sio_irq (void) __irq {
  volatile char dummy;
  volatile char IIR;
  struct buf_st *p;

  /*------------------------------------------------
  Repeat while there is at least one interrupt source.
  ------------------------------------------------*/

  while (((IIR = U1IIR) & 0x01) == 0) {
     switch (IIR & 0x0E) {
       case 0x06: /* Receive Line Status */
         dummy = U1LSR;  /* Just clear the interrupt source */
         break;

       case 0x04: /* Receive Data Available */
       case 0x0C: /* Character Time-Out */

         p = &rbuf;

         if (((p->in - p->out) & ~(RBUF_SIZE-1)) == 0) {
           p->buf [p->in & (RBUF_SIZE-1)] = U1RBR;
           p->in++;
         }
         break;

       case 0x02: /* THRE Interrupt */
         p = &tbuf;

         if (p->in != p->out) {
           U1THR = p->buf [p->out & (TBUF_SIZE-1)];

           p->out++;
           tx_restart = 0;
         }
         else {
           tx_restart = 1;
         }
         break;

       case 0x00: /* Modem Interrupt */
         dummy = U1MSR;  /* Just clear the interrupt source */
         break;

       default:
         break;
     }
  }

  VICVectAddr = 0; /* Acknowledge Interrupt */
}

int __swi(8) com_putchar (int c);
int __SWI_8              (int c) {
  struct buf_st *p = &tbuf;




  /*------------------------------------------------
  If the buffer is full, return an error value.
  ------------------------------------------------*/
  if (SIO_TBUFLEN >= TBUF_SIZE)
    return (-1);




  /*------------------------------------------------
  Add the data to the transmit buffer.  If the
  transmit interrupt is disabled, then enable it.
  ------------------------------------------------*/
  if (tx_restart)       {
    tx_restart = 0;
    U1THR = c;
  }
  else {
    p->buf [p->in & (TBUF_SIZE - 1)] = c;
    p->in++;
  }




  return (0);
}

int __swi(9) com_getchar (void);
int __SWI_9              (int c) {
  struct buf_st *p = &rbuf;

  if (SIO_RBUFLEN == 0)
    return (-1);

  return (p->buf [(p->out++) & (RBUF_SIZE - 1)]);
}