35
Both of the coding methods described above can also be used when using
both AND LD and OR LD, 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 nec-
essary to break block b down further, because it can coded directly using
only AND and OR.
0000
0001
0002
0003
0201
0101
0004
Block
a
Block
b
Address
Instruction
Operands
0000
LD
0000
0001
AND NOT
0001
0002
LD
0002
0003
AND
0003
0004
OR
0201
0005
OR
0004
0006
AND LD
---
0007
OUT
0101
Although the following diagram is similar to the one above, block b in the dia-
gram below cannot be coded without being broken down into two blocks
combined with OR LD. In this example, the three blocks have been coded
first and then OR LD has been used to combine the last two blocks followed
by AND LD to combine the execution condition produced by the OR LD with
the execution condition of block a.
When coding the logic block instructions together at the end of the logic
blocks they are combining, they must, as shown below, be coded in reverse
order, i.e., the logic block instruction for the last two blocks is coded first, fol-
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.
0000
0001
0002
0003
0102
0004
0202
Block
a
Block
b
Block
b2
Block
b1
Address
Instruction
Operands
0000
LD NOT
0000
0001
AND
0001
0002
LD
0002
0003
AND NOT
0003
0004
LD NOT
0004
0005
AND
0202
0006
OR LD
---
0007
AND LD
---
0008
OUT
0102
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.
Combining AND LD and
OR LD
Complicated Diagrams
The Ladder Diagram
Section 4-3
Summary of Contents for SYSMAC C20K
Page 1: ...Cat No W146 E1 5 Programmable Controllers SYSMAC C20K C28K C40K C60K ...
Page 2: ...K type Programmable Controllers OPERATION MANUAL Revised July 1999 ...
Page 3: ...iv ...
Page 5: ...vi ...
Page 19: ...7 SECTION 2 Hardware Considerations 2 1 Introduction 2 2 Indicators 2 3 PC Configuration ...