Omron SYSMAC C20K Operation Manual page 48

The Ladder Diagram
36
The following diagram must be broken down into two blocks and each of
these then broken into two blocks before it can be coded. As shown below,
blocks a and b require an AND LD. Before AND LD can be used, however,
OR LD must be used to combine the top and bottom blocks on both sides,
i.e., to combine a1 and a2; b1 and b2.
Block
a1
0000 0001
0002 0003
Block
a2
Block
a
Address Instruction
0000 LD
0001 AND NOT
0002 LD NOT
0003 AND
0004 OR LD
0005 LD
0006 AND
0007 LD
0008 AND
0009 OR LD
0010 AND LD
0011 OUT
This type of diagram can be coded easily if each block is worked with in or-
der first top to bottom and then left to right. In the following diagram, blocks a
and b would be combined with AND LD as shown above, and then block c
would be coded and a second AND LD would be used to combine it with the
execution condition from the first AND LD, and so on through to block n.
Block Block
a b
Block
b1
0004 0005
0006 0007
Block
b2
Block
b
Operands
0000
0001
0002
0003
---
0004
0005
0006
0007
---
---
0103
Block
c
Section 4-3
0103
Blocks a1 and a2
Blocks b1 and b2
Blocks a and b
00
Block
n