HP 9000 Series 300 Tutorials Manual page 164

Accessing the Interface Special Files
The Series 800 kernel is shipped with a default I/O configuration. This means
a default set of special files is made for you. For example, the /dev/hpib
directory contains special files created for use with HP-IB instruments
connected to the HP 27110B HP-IB interface. The special file /dev/gpioO is
created for use with instruments or peripherals connected to the HP27114A
Asynchronous FIFO interface (AFI). The
in sf
command is used to install
these special files all at one time.
Mknod
could also be used to create them
one at a time. For more information on
in sf
and
mknod
refer to the HP- UX
Reference.
Major Numbers
Major numbers map the hardware I/O cards to the software I/O driver for
the type of I/O application the card will be doing. The driver used to talk to
the HP-IB card for instrument I/O is called
instrO,
and corresponds to major
number 21. The HP-IB card talks to different drivers (which use different
major numbers) to do I/O to other kinds of devices, such as disc drives or
printers. All default special files in the /dev/hpib directory use major number
21. The driver that talks to the AFI card is called
gpioO,
and corresponds to
major number 22. The /dev/gpioO special file uses major number 22.
Minor Numbers and Logical Unit Numbers
Drivers use minor numbers to map the hardware I/O cards to their locations
in the Series 800 I/O backplane. The default I/O configuration shipped with
your Series 800 creates special files accessing a subset of the available backplane
slots. For the HP-IB card, two slots are available for instrument I/O, and one
slot is available for the AFI card. Slot information is accessed through the
device's logical unit number. The logical unit number is mapped into the
special file's minor number. For HP-IB special files, the HP-IB bus address is
also mapped into the minor number.
The minor number syntax for an HP-IB special file is:
OxOOLuBa
B-2 Series 800 Dependencies