Rockwell Automation 1772-AF1,D17726.5.1 User Manual MINI-PLC-2/15 - Manual (Page 40)

Programming
Chapter 3
3Ć32
Figure 3.28
AF1 Standard Deviation Function Format After Execution
17 16 15 14 13 12 11 10 7 6 5 4 3 2 1 0 Bit No.
Word
Input 1
S
Result Address
Result
D E
11589
ER
Input 2
Input 3
Number of Inputs
0 0 3 200
201
202
203
305
306
(0) (0) (1) (0)
2 0 0
2 0 1
2 0 2
0 0 0
8 1 6
Data
Address
E = Enable Bit (1 = Function in Progress)
S = Sign Bit (1 = Negative)
D = Done Bit (1 = Function Complete)
ER = Error Bit (Set if number of inputs = 0)
Entry and Display of Input and Result Values
Figure 3.29 shows one method you can use to enter values and display results of
an AF1 standard deviation function. Although there are several techniques for
accomplishing this, we chose the instructions. The first rung requests an AF1
standard deviation function. The top branch of the second rung shows the
number of values whose standard deviation is sought, 003, in word 200. it also
shows the three numbers involved in words 201, 202, and 203. The lower
branch of the second rung shows the resulting standard deviation as 000.816 in
words 305 and 306.
Error Message
If you insert a zero for the number of values whose standard deviation is sought,
the error bit (bit 14) is set and the result reads zero.