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SECTION
10.
PROCESSING INSTRUCTIONS
N'
is
the number of input scans
in
the last
averaging period
NT
is
the
total number of input samples
processed
in
the
Output Interval
INTERMEDIATE
STORAGE REOUIREMENTS
The number of Intermediate locations will
depend upon
the number of input values and
outputs desired:
1.
Define
K
as
the number of input values.
2.
Define
S
as
the maximum of either the
variances, standard deviations, or C, where
C
= K if K
<
the number of correlations
requested, or
C
= numberof correlations
+
1
if
K >
the
number of
correlations requested.
3.
Define Q as
the maximum of either the
covariances or correlations desired.
4,
Define
P
as the
total number of outputs
desired.
The amount of intermediate memory locations
(lML) required,
is
then given
by:
IML=K+S+Q+P+2
EXECUTION TIME
lf
K,
S, and Q are defined
as
in
the previous
section, the execution time
of
the CV/CR
Instruction in milliseconds
can be approximated
by:
T(ms)
=
1.1K
+
0.5S
+ 0'9Q +
1.8
When evaluating how
frequently input samples
can be processed
by
the CV/CR Instruction
(i.e.,
determining
the minimum program table
execution interval), the
time required to make
the measurements and order the input values
must be added to
the CV/CR execution time.
Two alternatives exist for
the measurement
portion
of
the programming. The fastest method
is
to group
as many sensors as possible into the
fewest measurement instructions, ignoring the
Input location
order required
by
the CV/CR
Instruction. After the measurements are made,
use
"ii1ove"
instructions (i.e., 31 and 54) to
obtain
the proper input
order. The
slower
alternative
is
to order separate measurement
instructions directly
as required
by
the CV/CR
Instruction. While avoiding "move" instructions,
this
approach uses more measurement
instructions. The reason the first method is
in
general
faster
is
that less overhead time
is
required in going from
one measurement to
another within
a
single instruction (using
the
"repetitions" feature)
than in going from one
measurement instruction
to another.
ln many situations, the 21X must perform
measurement and processing
tasks in addition
to those associated with
the CV/CR Instruction.
Uninterrupted operation of the CV/CR
Instruction
is
assured by entering it in Program
Table
1
(highest priority) and placing
the
additionaltasks in Program Table
2.
A covariance correlation example is given
in
Section
8.
*** 66
ARCTAN
***
FUNCTION
Calculate the angle
in
degrees whose
tangent
is
)(/Y.
The polarity of X and
Y must be known to
determine
the quadrant
of
the angle, as shown
here.
lf
0
is
entered
for Parameter 2, the
Arctangent of
X
is
the result (limits
of
the
function are
-90o <
ARCTAN <
90o).
Quadrant
Sign of
X
Sign of
Y
l++
ll
+
ill
lV+
PAR. DATA
NO. TYPE
DESCRIPTION
4
Input location of
X
txl
4
lnput location
of
Y
IYI
4
Destination input location
for
ARCTAN(X
r)
Input locations
altered:
1
01:
02:
03:
10-14
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