HP 54501A - Introduction

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