Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual User Manual

Page 127

Data Manipulation Instructions

Chapter 6

6Ć5

A Get/Les or Get/Equ pair of instructions forms a single condition for
logic continuity. Alone or with other conditions, each pair can be used to
energize an output device or other output instruction. In all cases, the Get
instruction must be programmed before the Les or Equ instruction. If other
conditions are also programmed, they should be entered before the Get
instruction or after the Les or Equ instruction.

Data comparisons are made by comparing a changing BCD value to
a reference BCD value. The reference value need not be fixed. The
following types of data comparisons of BCD values can be made:

< Less Than

> Greater Than

= Equal To

≤

Less Than or Equal To

≥

Greater Than or Equal To

Less Than – A less-than comparison is made with the Get/Les pair of
instructions. The BCD value of the Get instruction is the changing value.
It is compared to the BCD value of the Les instruction, the reference value
(Figure 6.5). When the Get value is less than the Les value, the comparison
is true and logic continuity is established.

Figure 6.5

LessĆThan Comparison

|ą|

(ą)

120 010

| G |

YYY

030

| < |
654

037

Reference Value

When YYY<654, GET/LES comparison is true and 010/00 is energized.

Greater Than – A greater-than comparison is also made with the Get/Les
pair of instructions. This time, the Get instruction BCD value is the
reference and the Les instruction BCD value is the changing value. The
Les value is compared to the Get value for a greater-than condition
(Figure 6.6). When the Les value is greater than the Get value, the
comparison is true and logic continuity is established.