Receiving Information From The Instrument - HP 54501A Programming Reference Manual

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