Tektronix 2221 - Page 96

1
Options
and
Accessories - 2221
Operators
Where a
header has
multiple arguments , the
arguments
( or argument pairs , if the argument has its own argument )
must be separated by commas . Two examples of this syn
tax
are :
the last data byte ; others use only the LF character as a
terminator . The GPIB interface can be set to accept either
terminator . With EOI selected , the instrument interprets
data byte
received with Eol
asserted as
the end of the
input
message ; it also
asserts EOI
concurrently
with the
last byte of an
output
message . With the LF
setting , the
instrument
interprets
the LF
character
without EOI
asserted ( or any data byte received with EOI asserted ) as
the end of an input message ; it transmits a Carriage
Return character followed by Line Feed ( LF with EO !
asserted ) to
terminate
messages .
DATA ENCdg : BINary , CHAnnel : CH2
and
VMOde
?
CH1 ,
CH2 ,
ADD
|
NOTE
With Option 12 , multiple commands ( especially
queries ) should not be used in a single programmed
message
line
.
Commands (
and
arguments to
commands ) are
interpreted and
acted on by
the
oscilloscope as soon as a separator is recognized ;
the oscilloscope does not wait for the message
terminator ( CA or CA - LF ) to signal the end of the
command line . If one of the commands in a
command
line
requires a
response
for any
reason
( i.e. , command
error , illegal
command , or unable
to
do the command ) , the oscilloscope's service - request
status - byte response will be asynchronously sent . If
the service request is not handled correctly , the
controller may not be able to
continue
with
its
program
.
RS - 232 - C MESSAGE
TERMINATOR - RS - 232 - C
messages
from the
oscilloscope
may be
terminated
with
either
carriage return ( CR
) or the CR
and line - feed
( LF )
characters . The RS - 232 - C Option can be set to send and
receive either
terminator
as
the last byte
of a
message
.
The instrument does not wait for the end - of - line terminator
when it handles incoming messages . It recognizes a semi
colon as the end of command terminator and immediately
begins
its
response to
the
preceding
command string .
Because of the way the instrument handles commands ,
messages
should
be
limited to
one
command per
line .
Incoming and
outgoing
messages
are not
stacked . If more
than one command per line is sent , responses to the first
commands in a line may be lost when the output buffer is
reinitialized to output the response to the last command in
a line . Even single command messages should not be
terminated twice . The response to the command may be
lost when the instrument sees the second terminator .
uu
COMMAND
SEPARATOR
-
Multiple
commands
may be
put into one command line by separating the individual
commands with a
semicolon
; for
example
:
COMMAND FORMATTING - Commands sent to the
oscilloscope must
have the
proper format
( syntax ) to
be
understood ; however , this format is flexible in that many
variations
are
are acceptable . The following paragraphs
describe this format and the acceptable variations .
DATA ENCdg : BINary , CHAnnel : CH2 ; WFMpre XINcr : 1.0E - 3
1
The
oscilloscope
expects all
commands
to be
encoded
as either upper
- case or
lower - case
ASCII
characters . All
data
output
is in
upper
case
.
Multiple commands in a message are not recommended
with RS - 232 - C controller routines for Option 12. See the
previous NOTE . However , the command separator is valid ,
and multiple
commands
on the
same
message line may be
used . A
waveform preamble is one
example
of using
multiple commands in a single message . With Option 10 ,
GPIB controller programs often use multiple commands in
a
single
line .
Spaces can be used as formatting characters to
enhance
the
readability
of
command sequences . As a
gen
eral rule , spaces
can be placed
either after
commas and
semicolons or after the space that follows a header .
GPIB
MESSAGE TERMINATOR - As
previously
explained , GPIB messages may be terminated with either
EOI or LF
.
Some
controllers
assert
EOI
concurrently with
NUMERIC ARGUMENTS - Table
7-16
shows
the
number formats for the < NR1 > , < NR2 > , and < NR3 >
arguments used in a command . Both signed and unsigned
numbers are accepted , but unsigned numbers are taken as
positive
.
7-20
U