HP 54501A - Devices; Poll Responses

Polling
HP-IB
Devices.
Parallel
Poll
is
the fastest
means
of
gathering
device
status
when several
devices
are
connected
to
the
bus.
Each
device
(with
this
capability)
can
be
programmed
to
respond
with
one
bit
of
status
when
parallel
polled.
This
makes
it
possible
to
obtain
the
status
of
several
devices
in
one
operation.
If
a
device
responds
affirmatively
to
a
parallel
poll,
more
information
about
its
specific
status
can
be
obtained
by
conducting
a
serial
poll
of
the
device.
Configuring
Parallel
Poll
Responses
Certain
devices,
including
the
HP
54501A,
can
be
remotely
programmed
by a
controller
to
respond
to
a
parallel
poll.
A
device
which
is
currently
programmed
for
a
parallel poll
responds
to
the
poll
by placing
its
current
status
on one
of the bus
data lines.
The
response
and
the
data-bit
number
can
be
programmed
by the
PPC
(Parallel
Poll
Configure)
statement.
Multiple listeners
cannot
be
specified
in
this
statement.
If
more
than
one
device
is
to
respond
on
a
single bit,
each device
must
be
configured
with a
separate
PPC
statement.
Example:
ASSIGN
©Device
to
707
PPOLL CONFIGURE
@Device;Mask
The
value
of Mask
(any
numeric
expression
can
be
specified)
is
first
rounded
and then used
to
configure
the
device's
parallel
response.
The
least
significant
3 bits
(bits
0
through
2)
of
the
expression
are
used
to
determine
which
data
line the
device
is
to
respond
on
(place
its
status
on).
Bit
3
specifies
the
"true"
state
of
the
parallel
poll
response
bit
of
the
device.
A
value
ofO
implies
that the
device's
response
is
0
when
its
status
bit
message
is
true.
Example: The
following
statement
configures
the
device
at address
07
on
the
interface select
7
to
respond
by
placing a
0
on
DI04
when
its
status
response
is
"true."
PPOLL
CONFIGURE
707;4
Message Communication
and System
Functions
3-36
HP
54501A
Programming