76
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
The following type of diagram can be coded easily if each block is coded in order:
first top to bottom and then left to right. In the following diagram, blocks a and b
would be combined using AND LOAD as shown above, and then block c would
be coded and a second AND LOAD would be used to combined it with the execu-
tion condition from the first AND LOAD. Then block d would be coded, a third
AND LOAD would be used to combine the execution condition from block d with
the execution condition from the second AND LOAD, and so on through to
block n.
0005
00
Block
a
Block
b
Block
n
Block
c
Complicated Diagrams
Mnemonic Code
Section 4-4
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