Gpib Operating Modes; Introduction; Talk-Only Mode - Racal Instruments 1994 Service Manual

4.5.3.
Untalk
(UNT)
4. 5. 3.
9.1 This universal
command
instructs
all
talkers,
including the counter,
to return
to
their untalk or talker-idle state.
All bus
members
are also
removed from
their talker
state
whenever
a talk
address other than
their
own
is
received.
In
the
Untalk
state, the
front-panel
ADDR
LED
is
turned
off.
The decimal
and hex equivalents are
9
and 5F,
respectively.
4.5.3.10 Unlisten
(UNL)
4.5.3.10.1 This universal
command
instructs
all
listeners,
including the counter,
to
return to their unlisten or
listen-idle state. In
the Unlisten state, the front-panel
ADDR
LED
is
turned
off.
The decimal and hex
equivalents are 63 and 3F, respectively.
4.6
GPIB
OPERATING
MODES
4.6.1
Introduction
4.6.1. 1
Before operating
the
counter on
the
GPIB, ensure
that the
instrument has
been
assigned
its
correct bus address
(see
Subsection
4.3)
and
that the correct
AC
line
voltage has been selected
(see
Subsection
2.7.2).
The
last
instruction
is
especially
important
if
the
1994
is
being
used for the
first
time
or at
a
new
location.
4. 6.
1.2
The 1994 can be operated on
the
GPIB
in
either
its
Talk-Only or Addressed
mode.
4.6.2
Talk-Only
Mode
4.
6.2.1
To
set the
counter
in this
mode,
place the "Talk
.
Only" switch of the
GPIB
switch bank
in its
logic "l" position.
The
GPIB
interface
is
now
in
the Talk-Only
mode
and the
settings
of switches
A1
to
A5
are irrelevant.
4.6»2.2
The
Talk-Only
mode
may
be used
in
systems
not
having
a controller.
Such
a
system
permits
remote
reading of counter
measurement
data,
however,
the instrument
is
controlled
from the front panel (see Section
3).
4. 6. 2. 3
The counter determines
the rate at
which
measurements
are
made. The
output
buffer
is
updated
at the
end
of each
measurement
cycle,
overwriting the previous
measurement
data
if
not transferred
to the listener.
4.6.
2.4
The
listener triggers
the transfer to
data
from
the counter.
The
counter's
output
buffer
is
cleared
when
data
transfer
is
completed.
4. 6. 2.
5 Differences
between
the
measurement
rate
and data
transfer trigger rate
are resolved as follows:
a.
If
data
transfer
is
in
progress
at the
end of
a
measurement
cycle,
updating of the output buffer
is
delayed.
Data
transferred
will
correspond
to
the previous
measurement
cycle
b.
If
data
transfer
is
requested during a
measurement
cycle
and
the
output buffer
is
empty, data
transfer
is
delayed
until
the buffer
is
updated.
Data
transferred
will
then
correspond
to
the
latest
measurement
cycle
4-20