com(7)                         DG/UX R4.11MU05                        com(7)


NAME
       com - Com Port Asynchronous Receiver/Transmitter (Intel Only)

SYNOPSIS
       com(node-id,port)

DESCRIPTION
       This is the Asynchronous Receiver/Transmitter driver for the COM
       ports.

       To configure a com port, you must add a device name entry of the form
       described above to the DG/UX system configuration file.  The
       parameters in a device name have the following meanings:

       ·   The node-id parameter is currently not used and, if set, should
           be set to 0.

       ·   The port parameter is a hexadecimal number in the range 1 through
           4 that distinguishes the various instances of the controller that
           are available.

       Com serial ports present the standard DG/UX terminal interface
       described in termio(7).

       The termio structure c_cflags option EXTB is not available.  PAREXT
       is not supported.  Differing input and output baud rates are not
       supported.  The stty options for hardware flow control via CD (cdxon)
       and isochronous hardware flow control (isxoff) are not supported, nor
       are the CDXON or ISXOFF flag of the x_hflag field of the termiox
       structure.

       For com ports with a built in fifo, the ioctl TS_COM_FIFO_DISABLE
       using streams I_STR ioctl interface can be used to turn off the fifo.
       The I_STR ioctl TS_COM_FIFO_ENABLE can be used to turn the fifo back
       on again.  The I_STR ioctl TS_COM_FIFO_STATUS can be used to
       determine the status of the fifo.  The fifo is turned on by default.
       The fifo state is persistent across opens and closes.

       /* Example of ISTR/TSCOMFIFODISABLE to disable internal fifo */

       #include <stdio.h>
       #include <sys/ioctl.h>
       #include <sys/types.h>
       #include <stropts.h>
       #include <fcntl.h>

       #define IOCTLTIMEOUT 60   /* An arbitrarily long time to wait   */

       main()
       {

       int                        ttyfd;
       int                        status;
       tscomfifostatustype    fifostatus;
       struct strioctl            streamioctl;

       ttyfd = open("/dev/async/line/com(0,3)", ORDWR | ONONBLOCK, 0);

       fifostatus.status     = -1;                  /* arbitrary value */
       streamioctl.iccmd    = TSCOMFIFODISABLE; /* disable fifo    */
       streamioctl.icdp     = (char *)&fifostatus;
       streamioctl.iclen    = sizeof(tscomfifostatustype);
       streamioctl.ictimout = IOCTLTIMEOUT;
       status = ioctl( ttyfd, ISTR, &streamioctl);

       if (fifostatus.status == TSCOMFIFOENABLED) {
           printf("The fifo was previously enabled.\n");
           }
       else {
           printf("The fifo was previously disabled.\n");
           }

       }


FILES
       When a com controller is configured, it creates a character-special
       device node for the serial port, using the pathname:

           /dev/async/line/com(node-id,port)


       The com(0,4) port I/O address space conflicts with some graphics
       cards.

       The chk.devlink command is responsible for creating and maintaining
       an additional link to each port device node, with a pathname of the
       form /dev/tty[0-9]*.  See the chk.devlink(1M) and devlinktab(4M) man
       pages for details.

       The IO addresses and IRQ lines for the com ports in a DG/UX system
       are typically as follows:

       Com Port   I/O Address           IRQ

       com(0,1)   0x3F8 - 0x3FF         4
       com(0,2)   0x2F8 - 0x2FF         3
       com(0,3)   0x3E8 - 0x3EF         5
       com(0,4)   0x2E8 - 0x2EF         7


EXAMPLES
       The following entries in a DG/UX configuration file configure the
       first two COM devices.

            com(0,1)
            com(0,2)

SEE ALSO
       termio(7), termiox(7), streamio(7), chk.devlink(1M), devlinktab(4M).


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