6-3
Section
Basic Ladder Diagrams
344
The first of each pair of conditions is converted to LOAD with the assigned bit
operand and then ANDed with the other condition. The first two blocks can be
coded first, followed by OR LOAD, the last block, and another OR LOAD, or the
three blocks can be coded first followed by two OR LOADs. The mnemonic code
for both methods is shown below.
00000
LD
00000
00001
AND NOT
00001
00002
LD NOT
00002
00003
AND NOT
00003
00004
OR LD
—
00005
LD
00004
00006
AND
00005
00007
OR LD
—
00008
OUT
20001
00000
LD
00000
00001
AND NOT
00001
00002
LD NOT
00002
00003
AND NOT
00003
00004
LD
00004
00005
AND
00005
00006
OR LD
—
00007
OR LD
—
00008
OUT
20001
Address
Instruction
Operands
Address
Instruction
Operands
Again, with the method on the right, a maximum of eight blocks can be com-
bined. There is no limit to the number of blocks that can be combined with the
first method.
Both of the coding methods described above can also be used when using AND
LOAD and OR LOAD, as long as the number of blocks being combined does not
exceed eight.
The following diagram contains only two logic blocks as shown. It is not neces-
sary to further separate block b components, because it can coded directly using
only AND and OR.
00000 00001
00002 00003
00201
20001
00004
Block
a
Block
b
Address
Instruction
Operands
00000
LD
00000
00001
AND NOT
00001
00002
LD
00002
00003
AND
00003
00004
OR
00201
00005
OR
00004
00006
AND LD
—
00007
OUT
20001
Although the following diagram is similar to the one above, block b in the diagram
below cannot be coded without separating it into two blocks combined with OR
LOAD. In this example, the three blocks have been coded first and then OR
LOAD has been used to combine the last two blocks followed by AND LOAD to
combine the execution condition produced by the OR LOAD with the execution
condition of block a.
Combining AND LOAD and
OR LOAD