Control Of; Dvm Inputs - Datron 1061A User Handbook Manual

All the
front panel
controls
(except 'Power',
'2/
4-wire
fT
and
'Local/
Remote Guard') are
programmable
via the interface,
in
addition
to
'Front/
Rear I/P
Select'
and
'Run/Cal-Calibration
Enable'
on
the rear panel.
Furthermore, other 61/71 features exist
which
are
only
programmable and
therefore
can only be used
if
the
IEEE
interface
is
fitted.
These
are
known
as
Superfast,
Double
trigger ratio.
Binary Program,
Binary
Dump
and Delay.
These
are
explained
in this
section
of the
handbook
under
'Programming
Instructions'.
From
the
example
given
earlier in this
section
it
may
be seen that the
DVM
requires
an address
command
followed
by a
series
of device
dependant messages
or
commands
to
change
the various range, function
and operating modes.
A
series
of these
commands
can be sent together
as
a
'program
string', e.g.
R4F3T7
=
programming
instructions
string
terminator
Each
string
will
contain
at least
one
programming
instruction,
details
of
which are
given
later,
but
before the instrument can take
any action
on
the
instructions,
it
must
receive
a terminate
signal at the
end of any
string.
The required terminators
are:
i)
The ASCII
character
or
ii)
EOI
(end or
identify)
with
the last
byte
of
the
string.
To
assist in
obtaining a
correct
set
of
programming
instructions, the
DVM
checks for
errors
in
the
string,
and
generates a service
request
(SRQ)
if
a
syntax error occurs or
if
an option
was
called for
but
not
Fitted.
The
full
range
of
commands
for
programming
the
DVM
is
given
in
Table
4.3.
The
precise
programming
details
for
each
command
are given
in
the next
section
under
PROGRAMMING
INSTRUCTIONS.
Programming
instructions
Control
of
DVM
inputs
Range.
R1 through
to
R7
configure the
instrument to a specific range,
while
R0
places the
instrument
in
auto-range.
Programming R1
or
R7
when
Ohms
is
not
selected
causes the
DVM
to set
itself
to
R2 and
R6
respectively.
Function.
FI
through
to
F7
configure
the
instrument
to
the required function.
Programming
a function
which
is
not
fitted will
generate
an option
select error.
Filter.
Programming Cl
introduces
an
additional
filter
into the
analog
circuitry.
Front/rear input selection. At
power
up, the
DVM
selects
front
or
rear
input
dependent
on
the
position of the rear panel control switch.
If
this
switch
is
set
to rear, selection
of front or rear
can be
accomplished
by
programming 10
or
II
respectively.
Triggers.
A
reading
may
be triggered
from
one
of four sources,
(
1
)
internally generated,
(2)
external
(see
section
3), (3)
front panel
manual
triggers
or
(4)
a
GET
(group execute
trigger)
via
the interface.
A
group execute trigger
is
a
standard
bus message
which
is
recognised
by
the
DVM
when
it
has
been
addressed
as a listener.
Programming
the
appropriate
trigger
code allows
one
or
more of these sources
to
initiate a
measurement
cycle.
When
the
DVM
is
programmed
to
accept
GET,
sending the
ASCII
character
@
or
J
as part of
the
program
string will
also
trigger
the instrument.
The
GET command
will initiate
a
measurement
cycle
if
one
is
not already
in
progress or
will
be
stored
until
the current
measurement
cycle
is
complete
in
order
to
initiate
a
second
cycle.
This
permits the
second
cycle to overlap the
processing of
data
from
the
previous
measurement
cycle to
increase overall
instrument
read
rate.
In the
same
way,
an external
trigger
received
during
the
processing of
data from an
earlier
measurement
cycle will
initiate
another
measurement
cycle.
External
triggers
received during the
measurement
cycle
will
be ignored.
4-5