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Codes
The
following
pages
list
and
describe the
programming
codes
which
determine
the
formation of
the
output
string.
The
codes
on
this
page
select specific
types of
ASCII
strings for
retrieval.
RecallA^erlfy
(code
V)
By
sending a
V
code
the controller interrogates the
4708
to
obtain information
about
its
present
status.
Unless
otherwise
stated,
the
output
strings
are
formatted
as
programmed by
K
and
L
codes.
The
V
codes
are as follows:
V0
-
The
present
Output
value
VI
-
The
present
Frequency
setting
V2
-
The
present functional
status.
The
response
to
V2
is
a standard
ASCII
string:
(space
R*F*0*G*S*W*Q*D*L*K
terminator).
The
func-
tions are
represented
by
the
same
numerics
as for pro-
gramming.
In addition, the
Output
Range
is
identified
by
a
lower
case
'r'
if
the
4708
is
programmed
in
au-
torange.
V3
-
Software
status
The
software
status
is
the part
number
and
issue
number
of
the
internal
program. This
is
formatted
as follows,
in
response
to
command
code V3:
(space
890077
-
numeric
terminator)
Part
No.
Issue
No.
(This
status
report
is
also available
manually
by
pressing
Error
key
then
Lim-.
The
firmware
issue
number
is
presented
on
the
MODE
display).
V4-V8-
'Stored'
Frequencies
Codes
V4
to
V8
recall
each of
the five
frequencies held
in volatile
memory
locations
FI
to
F5.
These
can only
be
set
or selected manually.
(Refer
to
pages
3-7
and
3-8).
The
range of legends
u-ansmitted
by
the
4708
is
listed
under
'String
Formatting
Commands
(K
and
L
Codes)'.
l-code (Aide
Memoire)
This allows
the user to identify
a
specific calibrator
with a
designator
up
to
16 characters
in
length,
stored
in
non-volatile
memory. The 4708 must
first
be
placed
in
the
CAL
mode
by
turning the
CAL
key
to
ENABLE
and
sending
the
W1
com-
mand.
Sending
the
I
command
will store the
subsequent
16
character
string
in
memory.
This
string
can be
recalled
using
the
X8
command.
N.B.
The I-command
and
the
W1
command
must
not
be
sent
in
the
same
sying.
Specification
Tolerance
(Per
unit
-
P codes)
The
P commands
give access
to
Spec
mode
over
the bus, also
setting the calibration interval:
P0
-
24
hour;
PI
-
90
day;
P2
- 1
year
On
being
commanded
by
P
code,
the
4708
calculates the
Output
Uncertainty
of
its
current
state (as
a
'per
unit'
fraction
of
the
output value)
and
generates
an
output
string
formatted
by
K
and
L
codes.
Legends
are transmitted as
pu
(per
unit).
Absolute
Limits of
Tolerance
In thiscase,
theUcommands
cause
the4708
to
calculate the high
or
low
limit
of
uncertainty
of
its
output value
against the
nominated
calibration
interval.
uo
-
Low
limit
24 hour
U1
-
Low
limit
90 day
U2
-
Low
limit
1
year
U3
-
High
limit
24 hour
U4
-
High
limit
90 day
US
-
High
limit
1
year
On
being
commanded,
the calculated
value
is
output
by
the
4708
in
an
output
string
formatted
by
K
and
L
codes.
Diagnostic Information
The
X
commands
recall
the contents
of
certain non-volatile
calibration
memory
locations.
The
values
recalled are
calibra-
tion
constants stored
at
the
most
recent Autocalibration.
They
are
used
in
the
computations
which
establish the
4708
output
level,
as corrections for
long-term
drift
in
the
analog
circuitry.
XO
-
Zero
Cal. Store
XI
-
Gain
Cal.
Store
in
DC,
LF
gain
+
HF
calibration
in
AC
X2
-
'STD'
calibration
gain
factor
X3
-
Zero
offset
)
X4
-
Gain
error
)
factory established
X5
-
Linearity (not
AC)
)
X6
-
Reference Divider
setting
X7
-
Not
used
in
4708
X8
-
Recall
message which was memorised
earlier
by
the
operator using
Code
I.
Activating the Recall
Transmission
The 4708
assembles
the appropriate
output
string
in
its
output
registers
in
response
to
the
V,
P,
U
or
X
command.
It
can
subsequently
be
released
onto
the
bus
by
addressing
the
4708
as
a
talker.
String
Formatting
Commands
(K
and
L Codes)
The
output
string
can
be
formatted
and
terminated
to
adapt
to
user's
requirements.
Scientific
or
Engineering
notation
can be
programmed,
with or without
descriptive legends.
Two
ex-
amples
are
given below.
Codes
LO
to
L3
configure
the
output
suing
notation:
LO
-
Scientific
notation
with legends
LI
-
Scientific notation,
no
legends
L2
-
Engineering
notation
with legends
L3
-
Engineering
notation,
no
legends
5-11
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