HP 54501A - Hp-Ib

Serial
Poll
The
HP
54501A
supports
the
IEEE 488.1
serial
poll
feature.
When
a
serial
poll
of
the
instrument
is
requested,
the
RQS
bit
is
returned
on
bit
6
of
the
status
byte.
Using
Serial
Poll.
This example will
show how
to
use
the
service
request
by
conducting
a
serial
poll
of
all
instruments
on
the
bus.
In
this
example,
assume
that
there
are
two instruments
on
the
bus;
an
oscilloscope
at
address
7
and
a printer
at
address
1.
These
address
assumptions
are
made
throughout
this
manual,
and
it
is
also
assumed
that
we are
operating
on
Interface
Select
Code
7.
The
program
command
for
serial
poll
using
HP
BASIC
4.0
is
Stat
=
SPOLL(707).
The
address
707 is
the
address
of
the
oscilloscope
in
this
example.
The
command
for
checking
the
printer
is
Stat
=
SPOLL(701)
because
the
address
of that
instrument
is
01
on
bus
address
7.
This
command
reads
the
contents
of the
HP-IB
Status
Register
into
the variable called
Stat. At
that
time
bit
6
of
the
variable
Stat
can
be
tested to see
if
it
is
set
(bit
6
=
1).
The serial
poll
operation can
be
conducted
in the
following
manner.
1.
Enable
interrupts
on
the
bus.
This
allows the
controller
to
"see"
the
SRQ
line.
2.
If
the
SRQ
line
is high
(some
instrument
is
requesting
service)
then
check the
instrument
at address
1
to see
if bit
6
of
its
status
register
is
high.
3.
Disable
interrupts
on
the
bus.
Message
Communication and
System
Functions
HP
54501A
3-32
Programming