Introduction - HP 54501A Programming Reference Manual

Waveform Subsystem
17
Introduction
The
WAVEFORM subsystem is
used to transfer waveform data between
a
controller and the
HP 54501A's waveform memories.
The waveform
record
is
actually contained in two portions, the waveform data and the
preamble. The waveform data is the actual data acquired
for
each
point
in
the specified source.
The
preamble contains
the information for
interpreting
the
waveform data. This includes the number of points
acquired, format
of acquired
data, and type
of acquired
data.
The
preamble
also
contains the X and Y increments, origins, and references
for the acquired
data, so
that the raw data can be translated to time
and
voltage
values.
The
values set in the preamble are determined when
the
:DIGITIZE
command
is executed or the front panel store key is
pressed.
The
Preamble values are based
on the settings of
variables in the
ACQUIRE
subsystem or the front panel setup
if
the store
key
is pressed.
Although
the
preamble
values can be changed with
a
controller, the way the data was
acquired cannot
be changed.
Changing
the
preamble values
cannot
change the type
of
data that was actually acquired, the number
of
points
actually acquired,
etc.
Therefore,
extreme caution must be used when
changing any waveform preamble values
to
ensure the data will still be
useful. For
example, setting
POINTS
in the
preamble to
a
value different
from the actual number
of points
in the waveform will result in inaccurate
data.
The
waveform data and preamble must be read
(by
the controller) or sent
(to the
HP
54501A) with two
separate commands,
DATA
and
PREAMBLE.
Sending
consecutive
:DIGITIZE
commands may improve the data
throughput. Refer to the
Root Level Command
:DIGITIZE
for
more
information.
HP 54501A
Programming
Waveform Subsystem
17-1