Omron C200H Operation Manual page 68

Basic Ladder Diagrams
Block
b1
00000 00001 00002 00003
00004 00202
Block
b2
Block Block
a b
Complicated Diagrams
Block Block
a1 b1
00000 00001 00004 00005
00002 00003 00006 00007
Block Block
a2 b2
Block Block
a b
lowed by the one to combine the execution condition resulting from the first
logic block instruction and the execution condition of the logic block third from
the end, and on back to the first logic block that is being combined.
When determining what logic block instructions will be required to code a dia-
gram, it is sometimes necessary to break the diagram into large blocks and
then continue breaking the large blocks down until logic blocks that can be
coded without logic block instructions have been formed. These blocks are
then coded, combining the small blocks first, and then combining the larger
blocks. Either AND LOAD or OR LOAD is used to combine the blocks, i.e.,
AND LOAD or OR LOAD always combines the last two execution conditions
that existed, regardless of whether the execution conditions resulted from a
single condition, from logic blocks, or from previous logic block instructions.
When working with complicated diagrams, blocks will ultimately be coded
starting at the top left and moving down before moving across. This will gen-
erally mean that, when there might be a choice, OR LOAD will be coded be-
fore AND LOAD.
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 LOAD. Before AND LOAD can be used, how-
ever, OR LOAD must be used to combine the top and bottom blocks on both
sides, i.e., to combine a1 and a2; b1 and b2.
Blocks a1 and a2
Blocks b1 and b2
Blocks a and b
The following type of diagram can be coded easily if each block is coded in
order: first top to bottom and then left to right. In the following diagram,
Address Instruction
00000 LD NOT
00502
00001 AND
00002 LD
00003 AND NOT
00004 LD NOT
00005 AND
00006 OR LD
00007 AND LD
00008 OUT
Address Instruction
00000 LD
00503 00001 AND NOT
00002 LD NOT
00003 AND
00004 OR LD
00005 LD
00006 AND
00007 LD
00008 AND
00009 OR LD
00010 AND LD
00011 OUT
Section 4-3
Operands
00000
00001
00002
00003
00004
00202
—
—
00502
Operands
00000
00001
00002
00003
—
00004
00005
00006
00007
—
—
00503
55