Omron SYSMAC C20P Operation Manual page 118

Converting to Mnemonic Code
Complicated Diagrams
Address Instruction
0000 LD NOT
0001 AND
0002 LD
0003 AND NOT
0004 LD NOT
0005 AND
0006 OR LD
0007 AND LD
0008 OUT
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. AND LD and OR LD is used to combine either, i.e., AND LD or OR
LD always combines the last two execution conditions that existed, regard-
less 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 LD will be coded before
AND LD.
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 Block
a1 b1
0000 0001 0004 0005
0002 0003 0006 0007
Block Block
a2 b2
Block Block
a b
Data
0000
0001
0002
0003
0004
0202
—
—
0502
Section 7–2
0503
111