Rockwell Automation 1772-AF4,D17726.5.3 User Manual, AUX FUNCT PROM - Manual (Page 44)

Programming
Chapter 3
3Ć36
If we enter a data address of 201 and a result address of 305, the AF4
establishes the data table format shown in Figure 3.32. The data address
eventually contains the operand. The result address (word 305) contains the first
three digits of the result and word 306 contains the last three digits.
Figure 3.32
AF4 Natural Log Function Format After Address Entry
17 16 15 14 13 12 11 10 7 6 5 4 3 2 1 0
Digit 1
(MSD)
Digit 2
Bit No.
Data Address
Digit 2
Operand
Digit 5
Result Address
Result
D E
E = Enable Bit (1 = Function in Progress)
D = Done Bit (1 = Function Complete)
MSD = Most Significant Digit
LSD = Least Significant Digit
11502
Digit 3
(LSD)
Digit 3
Digit 1
(MSD)
Digit 4
Digit 6
(LSD)
ER = Error Bit (1 = Input is 0)
ER
201
305
306
4. Enter the number for the operand.
You can enter this number from the keyboard of your industrial terminal or
through ladder diagram functions. Entry of operand = 648 produces the result
6.47389 when the natural log function executes. Figure 3.33 shows how the
result is stored.
Figure 3.33
AF4 Natural Log Function Format After Execution
17 16 15 14 13 12 11 10 7 6 5 4 3 2 1 0 Bit No.
Data Address Operand
Result Address
Result
D E
E = Enable Bit (1 = Function in Progress)
D = Done Bit (1 = Function Complete)
11503
ER = Illegal Operand (1 = Input is 0)
ER
201
305
306
(0) (1) (0)
6 4 8
6 4 7
3 8 9