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AST(4)                       Device Drivers Manual                      AST(4)

     ast - multiplexing serial communications interface

     ast0 at isa? port 0x1a0 irq 5
     com2 at ast? slave ?
     com3 at ast? slave ?
     com4 at ast? slave ?
     com5 at ast? slave ?

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

     Each ast device is the master device for up to four com devices.  The
     kernel configuration specifies these com devices as slave devices of the
     ast device, as shown in the 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.



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

NetBSD 9.99                     March 30, 1994                     NetBSD 9.99