HP 54501A - Receiving Information from the Instrument

Receiving
Information
from
the
Instrument
After
receiving
a
query
(command
header
followed
by
a question
mark),
the
instrument
interrogates
the
requested
function
and
places
the
answer
in
its
output
queue.
The
answer
remains
in
the
output
queue
until
it
is
read
or
another
command
is
issued.
When
read,
the
answer
is
transmitted
across
the bus
to
the
designated
listener
(typically a
controller).
The
input
statement
for
receiving
a
response
message from
an
instrument's
output
queue
typically
has
two
parameters;
the
device
address and
a
format
specification
for
handling
the
response
message.
For
example,
to read
the
result
of
the
query
command
:SYSTEM:LONGFORM?
you
would
execute
the
statement:
ENTER
<
device address
>
;SettingS
where
<
device address
>
represents
the
address
of
your
device.
This
would
enter
the
current
setting
for
the
longform
command
in the
string
variable
SettingS.
Note
All
results
for
queries
sent
in
a
program
message
must
be
read
before
another
program
message
is
sent.
For
example,
when
you
send
the
query
:MEASURE:RISETIME?,
you
must
follow
that
query
with
the
program
statement
ENTER Risetime$
to read
the
result
of
the
query and
place
the
result
in
a
variable
(Risetime$).
Sending
another
command
before
reading
the
result
of the
query
will
cause
the
output
buffer
to
be
cleared
and
the
current
response
to
be
lost.
This
will
also
cause
an
error
to
be
placed
in
the
error
queue.
Executing
an
ENTER
statement
before
sending a
query
will
cause
the
controller to wait
indefinitely.
The
actual
ENTER
program
statement
you
use when
programming
is
dependent
on
the
programming
language
you
are
using.
The
format
specification
for
handling
the
response
messages
is
dependent
on
both
the
controller and
the
programming
language.
HP
54501A
Programming
Introduction to
Programming an
Oscilloscope
1-13