NAME    [Toc]    [Back]

     ast - multiplexing serial communications interface

SYNOPSIS    [Toc]    [Back]

     ast0 at isa? port 0x1a0 irq 5
     ast1 at isa? port 0x2a0 irq 6
     com* at ast? slave ?
     or
     pccom* at ast? slave ?

DESCRIPTION    [Toc]    [Back]

     The ast driver provides support for  boards  that  multiplex
together up to
     four  EIA  RS-232C  (CCITT  V.28) communications interfaces.
Apparently the
     original master of hardware using this multiplexing protocol
was AST.

     Each  ast  device is the master device for up to four com or
pccom devices.
     The kernel configuration  specifies  these  com  devices  as
slave devices of
     the  ast  device,  as shown in SYNOPSIS.  The slave ID given
for each com
     device determines which bit in  the  interrupt  multiplexing
register is
     tested  to find interrupts for that device.  The port specification for
     the ast device is used to compute the base addresses for the
com subdevices
  and the port for the interrupt multiplexing register.

     On a real AST card, the jumpers are as follows:

     SW1-1  Turn ON for irq 2.  Default is OFF.

     SW1-2  Turn ON for irq 3.  Default is OFF.

     SW1-3  Turn ON for irq 4.  Default is OFF.

     SW2-1  Turn ON for irq 5.  This is ON for  the  first  card,
OFF otherwise.

     SW2-2   Turn  ON for irq 6.  This is ON for the second card,
OFF otherwise.

     SW2-3  Turn ON for irq 7.  Default is OFF.

     SW3-1  ``Compatible mode''.  The ast driver  needs  extended
mode, so leave
            this OFF.

     SW3-2  IO Address.  In extended mode, this should be OFF for
the first
            card at 0x1a0-0x1a7 and ON for  the  second  card  at
0x2a0-0x2a7.

     SW3-3  Interrupt sharing.  Default is OFF.

     SW3-4  Reserved, must be OFF.

FILES    [Toc]    [Back]

     /dev/tty0?

SEE ALSO    [Toc]    [Back]

     com(4), intro(4), isa(4)

HISTORY    [Toc]    [Back]

     The ast driver was written by Roland McGrath and placed into
the public
     domain.

OpenBSD     3.6                          March      30,      1994