SIO(4)                  GENIX Programmer's Manual                  SIO(4)



      NAME
           sio - eight port terminal i/o multiplexer

      DESCRIPTION
           The serial i/o board provides 8  communication  lines  with  partial
           modem control, adequate for GENIX dialup use.  Each line attached to
           the serial i/o board behaves as  described  in  tty(4).   Lines  may
           independently  be  set  to run at any of 16 speeds.  The encoding is
           given in tty(4); however, 200 baud is not supported and  19200  baud
           is available (although not recommended) using the EXTA setting.

           The sio driver currently takes an interrupt on every incoming  char-
           acter.   In  the  future  the driver may instead use the sio board's
           fifo and poll for input at each clock tick.

           The file /usr/include/sys/sio.h contains  definitions  and  declara-
           tions describing the sio board.

      FILES
           /dev/tty0[0-7]
           /dev/ttyd[0-7] dialups

      SEE ALSO
           tty(4)

      DIAGNOSTICS
           sio%d: unexpected interrupt %x.  The driver got an  unexpected  kind
           of interrupt.  The sio board can generate five different interrupts,
           one of which the driver  does  not  use.   Expected  interrupts  are
           I_DONE, signifying DMA completion, I_FIFO, indicating that an incom-
           ing character has arrived (or that the fifo is  3/4  full,  when  in
           C_INT_MANY   mode),  I_MODEM,  indicating  a  line  transition,  and
           I_ERROR, which is discussed  below.   The  unexpected  interrupt  is
           I_DIAG,  which the board generates when completing internal diagnos-
           tics.  Getting an unexpected interrupt is harmless  in  itself,  but
           may be a sign of trouble elsewhere.

           sio%d: fifo overrun.  The fifo overflowed, causing one or more char-
           acters to be lost.

           sio%d: dma transfer error.  The sio board has generated its  I_ERROR
           interrupt, which signifies an error in transferring information from
           main memory to the sio board, resulting  in  garbled  output.   This
           message is a sign of hardware trouble.











      Printed 11/16/83                                                        1