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Basic Concepts Section 2-1
General Structure of the
Ladder Diagram
A ladder diagram consists of left and right bus bars, connecting lines, input
bits, output bits, and special instructions. A program consists of one or more
program runs. A program rung is a unit that can be partitioned when the bus is
split horizontally. In mnemonic form, a rung is all instructions from a LD/LD
NOT instruction to the output instruction just before the next LD/LD NOT
instructions. A program rung consists of instruction blocks that begin with an
LD/LD NOT instruction indicating a logical start.
Mnemonics A mnemonic program is a series of ladder diagram instructions given in their
mnemonic form. It has program addresses, and one program address is
equivalent to one instruction. Program addresses contain six digits starting
from 000000.
Left bus bar
Input bit
Connecting line
Special
instruction
Output bit
Right bus bar
Rungs
Instruction blocks
Program Address Instruction (Mnemonic) Operand
000000 LD 000000
000001 AND 000001
000002 LD 000002
000003 AND NOT 000003
000004 LD NOT 000100
000005 AND 000101
000006 OR LD
000007 AND LD
000008 OUT 000200
000009 END
Example
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