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The following diagram requires first an OR LD and an AND LD to code the
top of the three blocks, and then two more OR LDs to complete the mne-
monic code.
0002 0003
0105
0000
0001
0004 0005
0006 0007
Address Instruction Operands
0000 LD 0000
0001 LD 0001
0002 LD 0002
0003 AND NOT 0003
0004 OR LD ---
0005 AND LD ---
0006 LD NOT 0004
0007 AND 0005
0008 OR LD ---
0009 LD NOT 0006
0010 AND 0007
0011 OR LD ---
0012 OUT 0105
Although the program will execute as written, this diagram could be redrawn
as shown below to eliminate the need for the first OR LD and the AND LD,
simplifying the program and saving memory space.
0002 0003
0105
0001
0000
0004 0005
0006 0007
Address Instruction Operands
0000 LD 0002
0001 AND NOT 0003
0002 OR 0001
0003 AND 0000
0004 LD NOT 0004
0005 AND 0005
0006 OR LD ---
0007 LD NOT 0006
0008 AND 0007
0009 OR LD ---
0010 OUT 0105
The following diagram requires five blocks, which here are coded in order
before using OR LD and AND LD to combine them starting from the last two
blocks and working forward. The OR LD at address 0008 combines blocks d
and e, the following AND LD combines the resulting execution condition with
that of block c, etc.
0105
0000
0003
0004
0006 0007
0001
0002
0005
Block e
Block dBlock c
Block b
Block a
Address Instruction Operands
0000 LD 0000
0001 LD 0001
0002 AND 0002
0003 LD 0003
0004 AND 0004
0005 LD 0005
0006 LD 0006
0007 AND 0007
0008 OR LD ---
0009 AND LD ---
0010 OR LD ---
0011 AND LD ---
0012 OUT 0105
Blocks d and e
Block c with result of above
Block b with result of above
Block a with result of above
The Ladder Diagram Section 4-3