xpdi(7)                             CLIX                             xpdi(7)



  NAME

    xpdi - Processed Data Interface

  DESCRIPTION

    The Processed Data Interface (PDI) is a bidirectional, half-duplex, 8-bit
    parallel port that physically resides on the Image System Interface (ISI)
    board.  The ISI board may reside on the Shared Resource (SR) bus of
    Intergraph 300- and 400-series workstations and servers.  The xpdi file
    uses the PDI port to transfer large amounts of data to or from external
    devices such as plotters, scanners, and various specialty hardware.

    Each ISI board supports a single PDI port.  The PDI port on the ISI board
    in the lowest SR slot number is referred to as channel 0, the next ISI
    board supports channel 1, and so on.

    To write to the PDI port, use pdi_write(), specifying a currently-open
    channel from pdi_open().

    To read from the PDI port, use pdi_read(), specifying a currently-open
    channel from pdi_open().  The PDI read interface is implemented with a
    hardware capability to reject large amounts of data.  For example, if a
    1/4-inch strip is needed from a scanner that always sends inch-wide
    strips, the PDI hardware can be set up to transfer only the data
    pertaining to the first 1/4-inch of each line in the strip.  The remainder
    of each line is discarded.  This reduces memory and time requirements.
    Note that this rejection is a function of the resolution and line width
    specified with pdi_setup().

    The xpdi file also supports the transfer of data from an external device
    directly to a graphics window on an Integrated Frame Buffer (IFB).  Refer
    to pdi_ifb(3) for more information on this capability.

    The PDI port generates an output signal that may be switched by the
    process controlling it.  One type of plotter uses this signal to envelope
    all data transfers pertaining to a single plot.  This signal is referred
    to as the write_valid signal and is manipulated with pdi_setup().

  RELATED INFORMATION

    Functions:  pdi_close(3), pdi_ifb(3), pdi_open(3), pdi_read(3),
    pdi_write(3), pdi_cancel(3), pdi_setup(3)











  2/94 - Intergraph Corporation                                              1