Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 122)

Chapter 8
Using Basic Instructions
8–3
These instructions operate on a single bit of data. During operation, the
controller may set or reset the bit, based on the logical continuity of the rung.
You can address a bit as many times as your program requires.
Important: Using the same address with multiple output instructions is not
recommended.
Bit instructions are used with the following data files:
•
Output (O) and input (I) data files. These represent external outputs and
inputs.
•
The status data file (S). These values are used to configure and provide
controller status.
•
The bit data file (B). These are the internal coils used in your program.
•
Timer, counter, and control data files (T, C, and R). These instructions
use various control bits.
•
The integer data file (N). Use these addresses (at the bit level) as your
program requires.
LD, AND, and OR are all normally open instructions used in your program
to determine if a bit is On. If the bit addressed is on (1) when one of these
instructions is executed, then the instruction is evaluated as true. If the bit
addressed is off (0) when one of these instructions is executed, then the
instruction is evaluated as false. Refer to chapter 16 for instruction list
examples of when to use the LD, AND, and OR instructions.
Important: The bit AND and bit OR instructions discussed here differ from
the word AND and word OR output instructions described in
chapter 11.
Bit Address State LD, AND, and OR Instruction
0 False
1 True
Examples of devices that turn on or off include:
•
a push button wired to an input (addressed as I/4)
•
an output wired to a pilot light (addressed as O/2)
•
a timer controlling a light (addressed as T3/DN)
Using LD
Use the LD instruction for normally open contacts that appears first on a
rung or block.
Entering the Instruction
You enter the instruction from within the program monitor functional area.
P 0 0 0
I / 6 0
Bit Instructions Overview
1.54
False True
1.72 LD
1.94 2.12 AND
1.94 2.12 OR
] [
Execution Times (
µ
sec) when:
Ladder representation:
Load (LD), And (AND),
and Or (OR)
To access the LD instruction, press:
7
LD