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EXAMPLE
PROGRAMS
APPENDIX
P
The terms
IEEE-488
buss and GPIB (General
purpose
interface
buss)
are
used
synonymously
in
this
manual.
The IEEE-488
buss
was
developed
by the Hewlett
Packard
Company and was initially
known
as the HP-IB
(Hewlett
Packard
Interface
Buss).
As its
use spread
to
other
instrument
companies,
the
buss
structure
earned
itself
the
name GPIB (General
Purpose
Interface
Buss)
and finally
the
Institute
of Electrical
and Electronic
Engineers
(IEEE) generated
standard
number
488 covering
all
aspects
of buss configuration
and
operation,
hence
IEEE-488.
In
Europe,
the
International
Electrotechnical
Commission
developed
an equivalent
standard,
IEC 625-2 which
defines
an interconnect
buss that
is electrically
similar
to IEEE-488
but
uses a different
connector
system.
As an example,
we shall
examine
a program
to read
data
from
a
Keithley
Model
175 digital
multimeter
setup
on the buss as device
#12.
The first
step
is
to
initialize
the
IE-488
board,
this
applies
whatever
you intend
to do later
and would
usually
be
performed
at the beginning
of a program.
It
is not necessary
to
repeat
this
operation
unless
your
computer
is
turned
off.
To
initialize,
we make use of
the
SYSCON (system
configuration)
command.
100 DEF SEG = &HCOOO
'This
first
line
tells
the
CALL statement
that
follows
where
to
find
the
IE-488
ROM firmware
routine.
The
address
Hex COO0 corresponds
to
the
setting
of
the
MEMORY ADDRESS switch
on the board.
See the
IBM BASIC
manual
for
the action
of DEF SEG.
110 CMD$ = "SYSCON MAD=3, CIC=l,
NOB=l,
BAO=LH300"
'The command string
does the following:-
SYSCON = command
MAD = 3 sets
the
IBM talk/listen
address
to 3.
The device
address
for
the
IBM is
set
in software
instead
of by switch.
CIC =1
specifies
that
the
board
will
be the
buss controller.
Only
one device
can
be controller
at a time.
NOB = 1
We only
have 1 IE-488
board
installed
in our computer.
BAO = &H300
The base I/O address
through
which
all
data
will
be transferred
must be
known
by
the
firmware.
This
corresponds
to the setting
of the BASE
ADDRESS switch
on the board.
Page 43
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