PARALLEL(HW)                         UNIX System V



     Name
          parallel - parallel interface devices


     Description
          There are several parallel devices:

          /dev/lp0  Main parallel adapter.

          /dev/lp1  Adapter on monochrome video card.

          /dev/lp2  Alternate   parallel   adapter   (on   appropriate
                    machines).

          It is not possible to have all three parallel devices on one
          system.   Some  AT  computers  allow the use of two parallel
          devices,  /dev/lp2,  and  either   /dev/lp0   or   /dev/lp1.
          However, available devices vary from machine to machine, and
          may instead allow either /dev/lp0, or and  either  /dev/lp1,
          and /dev/lp2.

          If a  parallel  device  fails  to  interrupt  properly,  the
          parallel  driver  enters ``poll mode.''  Once interrupts are
          received from the device, the driver returns to its original
          mode.

          The parallel driver delays a certain amount of time  when  a
          parallel  device  is closed.  The amount of delay can affect
          printer performance, but  is  necessary  to  compensate  for
          different  sizes of printer buffers and printer speeds.  For
          example, this command sets the delay on close to  1  second,
          specified in 10ths of a second:

               stty time 10< /dev/lp0

          When given from a prompt, this command will only work if the
          port  is  open.   It is recommended that a variation of this
          command be placed in the  interface  script  used  with  the
          parallel device to achieve the same results:

               stty time 10 0< &1


     Notes
          Parallel  adapters  on  add-on  cards  will  function,   but
          switches  must  be set correctly.  Some compatible computers
          have ports lp0 and lp1 reversed.

          The stty(C) command for output processing is supported on  a
          parallel  device.   stty  options  that  have no effect on a
          parallel device  are  ignored  and  no  error  messages  are
          displayed.


     Usage
          Usually invoked by lp(C), but can be written to directly.


     Files
          /dev/lp0
          /dev/lp1
          /dev/lp2


     See Also
          lp(C), lp(HW), lpadmin(ADM), lpsched(ADM), serial(HW)


     (printed 2/15/90)                               PARALLEL(HW)