The
full
precision
of the frequency
setting cannot be
represented in the
4-byte
version
of
the IEEE
754 format. So, if full precision is
required,
a
separate
FR? command
should be
sent.
The frequency can then
be
read in
ASCII format.
No
separators
or terminators are used, as they
cannot
be
distinguished from binary
data.
However,
if the output
terminator
selected
from [GPIB
CONFIGURE] is
either
cr +
EOI or
cr,lf
+ EOI, then the
GPIB signal EOI ( End or
Identify) is asserted
with
the
last byte.
The
output rate
is the same as that
of the ASCII port,
approximately 1 byte per
millisecond, but
the data is
compressed. Also, the instrument’s
internal computation
time is much less.
No
headings are
available and the
last result is not re-output
after menu changes.
Use the
'DO' remote
command to read the
last result again,
e.g.
after changing the
DISPLAY SOURCE.
2.5 SERIAL
POLL
The
instrument can be configured to
request service from a GPIB
controller when
a
particular event has occurred, e.g. on end
of
sweep,
or data ready. The
controller may
then conduct a
serial poll to find
the source of the request. In a
serial poll the
controller
examines the status byte of
each device in turn.
2.5.1 The Status Byte
The status byte
register (read only)
holds the status of all events for
which it is
possible to request
service.
The
status
byte can be
read
by a
serial poll command
(which
clears the RQS
bit) or by
an
*STB?
command
(which leaves
the byte
unchanged).
The status
byte register is cleared by the commands
break (BK), clear status (*CLS),
reset (*RST),
initialize (TT1) and reset (TT2), and on
power-up.
128 64 32 16 8
4
2
1
END
OF
FILE
RQS ESB MAV END
OF
PLOT
ENDOF
SWEEP
ENDOF
MEASURE
ENDOF
PROGRAM
The
significance of these bits is as
follows:
Bit
Event
128 End of
file
64 RQS
(Continued
overleaf)
Comments
Set when the end of file is reached,
either
after a list
file
command or
when
filing data. Cleared by the
list file
command, the
clear
file
command, or by adding more data
to
the file (except
when
file is full).
Request service.
Set
when there is
a
correspondence
between one or more of the
bits set
in the status byte
register and one or more of
the
bits
set
in the service
request enable register.
Cleared by a
serial poll or an
*SREn command.
JWS/1260/2
7.7
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