84
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.
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, followed 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.
Block
a
Block
b
Block
b2
Block
b1
0000
00
0000
01
0005
02
0000
02
0002
02
0000
03
0000
04
Address Instruction Operands
00000 LD NOT 000000
00001 AND 000001
00002 LD 000002
00003 AND NOT 000003
00004 LD NOT 000004
00005 AND 000202
00006 OR LD —
00007 AND LD —
00008 OUT 000502
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, 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 start-
ing at the top left and moving down before moving across. This will generally
mean that, when there might be a choice, OR LOAD will be coded before 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, however, 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.
Block
a
Block
b
Block
b2
Block
b1
Block
a2
Block
a1
0000
02
0000
00
0005
03
0000
04
0002
07
0000
01
0000
03
0000
05
0000
06
Address Instruction Operands
00000 LD 000000
00001 AND NOT 000001
00002 LD NOT 000002
00003 AND 000003
00004 OR LD —
00005 LD 000004
00006 AND 000005
00007 LD 000006
00008 AND 000007
00009 OR LD —
00010 AND LD —
00011 OUT 000503
Blocks a1 and a2
Blocks b1 and b2
Blocks a and b
Complicated Diagrams
Mnemonic Code Section 4-4
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