Tektronix 2221 - WAVEFORM TRANSFERS; Waveform Preamble and Data Encoding

Options and Accessories — 2221 Operators
Table 7-16
Numeric Argument Format for Commands
A typical
response to the
preamble query
for an X - Y
acquisition
is :
C
Numeric
Argument
Number
Format
Examples
<
NR1 >
Integers +1 , 2 ,
-1 ,
-10
WFM WFI : “
ACQ , XY ,
0.2V , DC ,
50.0mV , DC ,
1.0uS ,
SAMPLE , CRV # 4 " ,
NR.P : 2048 , PT.O : 216 , PT.F : XY , XMU : 8.0E - 3 ,
XOF : , XUN : S , XIN : 20.0E - 9 , YMU : 2.0E - 3 , YOF : ,
YUN :
V.ENC : BIN , BN.F :
RP , BYT : 1 ,
BIT : 8 , CRV :
CHK ;
<< NR2 >
<
NR3 >
Explicit decimal point -3.2 , +5.1 , 1.2
Floating
point
in
+ 1.E -
2 ,
1.0E
+
2 ,
scientific
notation 1.E - 2 , 0.02E + 3
7
Л
П
П
n
n П
П
n
n
1
1
These replies are single line messages that end with
the selected message terminator ( CR or CR - LF ) . With the
GPIB interface , Edl ( end - or - identify ) is also sent if that ter
minator mode is selected .
WAVEFORM
TRANSFERS
Transferring
Waveforms
The
oscilloscope can
respond
with
the
preamble only ,
the curve data only , or the preamble and curve data
together
.
The
queries
to
obtain these
responses are , in
order , WFMpre ?, CURVe ?, and WAVfrm ?
The instrument can transmit and receive waveforms . It
can
transfer
these
waveforms in
binary
,
hexadecimal ,
or
ASCII encoding . When sending waveforms to the instru
ment , the target must be one of the numbered reference
memories ( REF4 only for the 2220 and 2221 ) . Waveforms
transferred from
the
oscilloscope
to the
controller may be
from either the
current
acquisition or one of the
numbered
reference
memories
(
again REF4
for the
2220 and
2221 ) .
The data source ( the memory location from which the
waveform
data
comes
)
and the
data
target ( the
memory
location
where
data
sent to
the
oscilloscope ends
up ) are
selected
independently .
For the
combined
response to
WAVfrm ?, the
preamble
is separated from the curve data by a semicolon ( ; ) .
Waveform Preamble
The waveform preamble contains the attributes for the
associated waveform data . These attributes include the
number of points per waveform , scale factors , vertical
offsets ,
horizontal
increment
, scaling
units , and
data
encoding . The preamble information is sent as an ASCII
encoded string in all cases . The exact attributes sent
depend on the waveform and the acquisition mode .
The preamble information is always formatted as ASCII
characters . Waveform ( CURVE ) data internal to the oscil
loscope is stored as 8 - bit , unsigned integers . Before that
data
is
sent via
the
Communications
option
, it
is
changed
into one of
three
formats
:
binary ,
hexadecimal , or
ASCII .
The
resolution of the
formatted
data
points
may
be
either
8 - bit or
16 - bit .
Waveform
record
length is
1024
data
points
for the
shortest
or
4096 data
points
for the
longest
.
The
number of bytes that are required to transfer data
depends
on
several
variables
. See
the
NR.Pts
description
in the
Waveform
Preamble Fields
command table for more
information . The
largest
number
of
curve data
bytes ever
needed
to
send a
waveform
is
8192
bytes ( for a 4K
record
that has
two
bytes
per
data
point
)
.
П
П
n
n
Л
A typical response to the preamble query WFMpre ? for
a Y ( time - implied ) acquisition is :
WFM WFI : “
ACQ
,
CH1,0.5V , DC ,
0.2mS
,
SAMPLE ,
CRV # 1 " ,
NR.P : 4096 , PT.O
: 122 , PT.F : Y ,
XMU : 0.0E0 ,
XOF : 0.XUN : S.XIN :
2.0E - 6 ,
YMU :
20.0E - 3 , YOF :
-20 , YUN
: V , ENC :
HEX , BN.F : RP
,
BYT : 1 , BIT : 8 , CRV : CHK ;
Binary
Encoding
BINary data is
transferred as
unsigned
binary
integers
.
Each data point in the record is either 8 bits or , when
averaged , 16 bits . BINary encoding format has the follow
ing waveform
curve data
form :
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