56
Basic Concepts Section 2-1
5. Rungs Requiring Caution or Rewriting
OR and OL LD Instructions
With an OR or OR NOT instruction, an OR is taken with the results of the lad-
der logic from the LD or LD NOT instruction to the OR or OR NOT instruction,
so the rungs can be rewritten so that the OR LD instruction is not required.
Example: An OR LD instruction will be needed if the rungs are programmed
as shown without modification. A few steps can be eliminated by rewriting the
rungs as shown.
Output Instruction Branches
A TR bit will be needed if there is a branch before an AND or AND NOT
instruction. The TR bit will not be needed if the branch comes at a point that is
connected directly to output instructions and the AND or AND NOT instruction
or the output instructions can be continued as is.
Example: A temporary storage bit TR0 output instruction and load (LD)
instruction are needed at a branch point if the rungs are programmed without
modification. A few steps can be eliminated by rewriting the rungs.
0000
00
H00000
0000
03
0000
01
H00000
0002
06
0000
02 T0001
TIM 0001 #0100
000003
0100
000000
000001
000002
H00000
H00000
0001
T0001
000206
LD
OR
OR
OR
OUT
TIM
AND
OUT
AND NOT
10 sec
Instruction Operand
Reset input
Error input
Error display
If a holding bit is in use, the ON/OFF status would
be held in memory even if the power is turned OFF,
and the error signal would still be in effect when
power is turned back ON.
0000
00
0000
01
0002
07
0002
07
0000
01
0000
00
0002
07
0002
07
0000
00
0000
01
0002
08
0000
00
0002
09
0002
09
TR0
0002
08
0000
01
Output instruction 2
Output instruction 1
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