Omron SYSMAC C200HS Operation Manual page 115

Inputting, Modifying, and Checking the Program
Interlocks
When drawing a ladder diagram, be careful not to use TR bits unless necessary.
Often the number of instructions required for a program can be reduced and
ease of understanding a program increased by redrawing a diagram that would
otherwise required TR bits. In both of the following pairs of diagrams, the bottom
versions require fewer instructions and do not require TR bits. In the first exam-
ple, this is achieved by reorganizing the parts of the instruction block: the bottom
one, by separating the second OUTPUT instruction and using another LOAD in-
struction to create the proper execution condition for it.
Note Although simplifying programs is always a concern, the order of execution of in-
structions is sometimes important. For example, a MOVE instruction may be re-
quired before the execution of a BINARY ADD instruction to place the proper
data in the required operand word. Be sure that you have considered execution
order before reorganizing a program to simplify it.
Note TR bits are only used when programming using mnemonic code. They are not
necessary when inputting ladder diagrams directly. The above limitations on the
number of branching points requiring TR bits, and considerations on methods to
reduce the number of programming instructions, still hold.
The problem of storing execution conditions at branching points can also be
handled by using the INTERLOCK (IL(02)) and INTERLOCK CLEAR (ILC(03))
instructions to eliminate the branching point completely while allowing a specific
execution condition to control a group of instructions. The INTERLOCK and IN-
TERLOCK CLEAR instructions are always used together.
TR 0
00000 00001
00000
00001
00000
TR 0
00001 00002
00004
00001 00002
00000
00001 00004
Section 4-7
Instruction 1
Instruction 2
Instruction 2
Instruction 1
00003
Instruction 1
Instruction 2
00003
Instruction 1
Instruction 2
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