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The
of
the low resolution format
is
significant digits when the
first (left
7 or
greater (Table
2.2-2). Thus,
it
SECTION
2.
INTERNAL DATA STORAGE
0.0000305. A description of Campbell
Scientific's
floating point format may
be
found
in
the description
of
the J and
K
lelecommunications commands
in
Appendix
C.
2.3
DISPLAYING STORED DATA
ON
KEYBOARD/DISPLAY . *7 MODE
The
*7 Mode is used to display Final Storage
data.
Enter
the Mode by keying
*7.
The display
willshow
"OT:XXXXX",
where
XXXXX
is
the
Final Storage location (DSP) where
the next
data
will
be
stored.
Two options are available:
1.
Press A to advance and display the
output
array lD of the oldest array
in
FinalStorage.
2.
Enter
a Final Storage location number.
When A is pressed, the DPTR
willjump
to
the location entered and, if it is not at
the start of
an array, advance to the first
start of array. The display
willshow
the
Array
lD.
Repeated use
of
the A key advances through
the output array,
while use
of
the B key backs
the DPTR through memory.
The Final Storage location of the data point
being
viewed may be displayed by keying
#.
At
this point, another location may be entered,
followed
by
A
to
jump to the start of the output
array equal to
or
just ahead
of
the location
entered.
Whenever
a location number
is
displayed by keying
#,
the corresponding data
point can be displayed by keying
C.
To advance
to
the start
of
the next output array, key
#A.
To
back
up
one output
array key
#8.
TABLE
2.3-1. "7 Mode Command Summary
Key
Action
Advance
to next data point
Back-up
to previous data point
Display location number of currently
displayed data point value
Display value of
current location
Advance to start of next output array
Back-up
to previous outout arrav
reduced
to
most) digit
may
be
to use high resolution output
or an offset
maintain the
desired resolution
of
a
.
For
example,
if
water level
is
to
be
red and output to
the nearest
0.01
foot,
the
must
be less than 70 feet for low
resolution
oltput
to display the 0.01 foot
increment.
lf the
water level
is
expected to
range from
F0
to 80 feet the data
could either be
output in hi$h resolution or
could be otfset by 20
feet. (transfprming the range to 30 to 60 feet.).
TABLE
Decimal Location in Low
Resolution Format
Value
Decimal Location
X.XXX
XX.XX
XXX.X
XXXX.
6.999
69.99
699.9
6999.
While outprit data have the limits described
above,
the $omputations performed
in
the 21X
are
done
in
lfloating point
arithmetic.
Values are
rounded
wfen
converting
to Final Storage
Format.
2.2.2
rNpUT
AND
TNTERMEDTATE
STORAGE
DATA FORMAT
In Input
and Intermediate Storage, numbers are
stored and
processed in a binary format with a
23 bit binary mantissa and a 6 bit binary
exponent. The largest and smallest numbers
that
can be stored and processed are
9
x
1018
and
1
x
10-'!e,
respectively. The size
of
the
number detbrmines
the resolution
of
the
arithmetic.
f,
rough
approximation
of
the
resolution
id
that it is better than
1 in
the seventh
digit.
For
ei<ample,
the resolution of 97,386,924
is better
than
10.
The resolution of
0.0086731q24
is
better
than 0.000000001.
A precise calculation of
the resolution of
a
number may be determined
by representing the
number as
a mantissa between
.5
and
1
multiplied by
2 raised to some integer power.
The resolution
is
the product
of
that power of
2
and
2-24. Fpr example, representing 478 as
.9336
* Zs,
Jne
resolution
is 2e
*
2'2a
-
2'15
-
0-
7-
70
700
A
B
#
c
#A
#B
2-3
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