Tektronix 2221 - RS-232-C PROGRAMMING

Options
and
Accessories
-
2221
Operators
FLOW
Control
is being transmitted , the PLOT indicator will be lit , and
new
waveform data
will not be
acquired
until
the
transmission is done .
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When transmitting data using modems to interconnect
two devices via the telephone lines , the normal handshak
ing lines are not used . The two devices can still communi
cate using a data - transmission technique called " flow
control
. "
Using this
method
,
the data
sent can
be
separated
from
non - data
being
received
(
such as noise )
.
This is done
by
interpreting every
correctly framed data
pattern
as
a valid
character and
constantly
checking for
two specific characters that turn the transmission on
and off .
Reset Under Communication Option Control
Certain default
settings for
acquisition and plot
modes
may be set up sending the INIt command . The INlt com
mand
does not
invoke the
power
- up
test .
Upon completion
of the INIt command , no status byte or event code
is generated .
The default settings are as follows :
These flow -
control
characters are
called
XON
(
transmis
sion on )
and
XOFF (
transmission off ) .
The usual
assign
ment for
these is <
control
- Q > for
XON and <
control
- S >
for XOFF ,
though
the
specific
characters
chosen
are a
function of the
communications
program
used
.
When
com
munication over
telepnone lines , flow
control
greatly
increases the
chance that ASCII
or HEX
encoded
data
will
be correctly
transferred
.
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The
FLOW ON
command
allows the
oscilloscope
some
on / off
control
of
the data
transfer
.
At
power - on , the
default
data encoding is BINARY . Flow control can not be used
for the
transmission of binary -
encoded
waveform
data
, so
the power - on setting of FLOW is set to off . Before sending
binary - encoded data , FLOW OFF must be sent if flow con
trol was previously set ON . The Advanced Functions menu
of the
2230 also has
menu choice for setting
flow
control
,
ACQUISITION REP : AVE
ACQUISITION
HSREC
:
SAMPLE
ACQUISITION LSREC :
PEAKDET
ACQUISITION SCAN :
PEAKDET
ACQUISITION ROLL : PEAKDET
ACQUISITION
SMOOTH
: ON
ACQUISITION
WEIGHT : 4 ( 16 in
the 2220
and 2221 )
ACQUISITION NUMSWEEP :
ACQUISITION VECTORS : ON
DATA
ENCDG
:
BINARY
DATA SOURCE : ACQ
DATA
TARGET
:
REF1
(
REF4
in
the
2220 and
2221
)
PLOT GRAT : OFF
PLOT
FORMAT : <
power - on
setting >
READOUT ON
a
Remote -
Local
Operating States
Menu
system
reset
.
The following paragraphs describe the two operating
states of the instrument : Local and Remote .
RS - 232 - C
PROGRAMMING
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REMOTE
OFF
( LOCAL ) -With
REMOTE
OFF ,
instrument
settings are
controlled
manually by the
operator using the front - panel controls . Option interface
messages such as REMOTE ON , RQS ON , and OPC ON
are
received and
executed .
Queries about
instrument's
states or measurement results will be answered . Device
dependent
commands that
require
an
instrument
operating
mode change to
be made cause
an
execution error , and a
service request will be generated if RQS is on .
Things to
consider
when
writing
programs
for
your
RS -
232
- C
controller
are given
here
to
help
you
when
you
must develop your own interfacing software . Before a pro
gram can be used to control the oscilloscope , the
RS - 232 - C
communication
parameters for
baud
rate ,
line
terminator , and parity must be set . Settings for these
parameters are selected and set using the RS - 232 - C
PARAMETERS
switch
found
on
the
side
panel of the
oscilloscope .
REMOTE
ON
( REMOTE ) - In
this
state
,
the
oscilloscope executes all commands sent to it . Remote
controllable front - panel indicators and CRT readouts are
updated as commands are carried out . There is no local
lockout ( LLO ) .
Changing
any
option -
controllable front -
panel
setting locally overrides the remote settings . If a waveform
Controller
programs are
usually composed of
two main
parts or
routines
. The two
parts are
generally
called
the
command
handler and
the
service -
request
handler .
C
7-15