Programming
Chapter 3
313
4. Enter values for operands 1 and 2.
You can enter these values from the keyboard of your industrial terminal or
through ladder diagram functions. Entry of operand 1 = 102746 and operand 2
- 256384 produces the result -153638 when the subtraction function executes.
Figure 3.8 shows how the result is stored.
Figure 3.8
AF1
Subtraction Function Format After Execution
171615141312111076543210
S
02
Bit No
Data Address
Operand 1
Operand 2
S
Result Address
Result
DERE
E = Enable Bit (1 = Function in Progress)
S = Sign Bit (1= Negative)
D = Done Bit (1 = Function Complete)
ER = Error Bit (1 = Overflow)
11486
201
202
203
204
305
306
(0)
S
(0)
1
467
562
843
531
386
(0) (1) (1) (0)
Entry and Display of Input and Result Values
Figure 3.9 shows one method for inserting input values and displaying input
values and results of AF1 subtraction computations. Although there are several
techniques for accomplishing this, we chose get instructions. The first rung
requests an AF1 subtraction. The second rung shows the two operands in its top
branch and the resultant difference in its lower branch.
