Introduction to Programming
Chapter 4
46
CAUTION: The Output Energize instruction can be
programmed unconditionally for some types of specialized
programming. Its use should be limited to storage bits for these
special purposes. An unconditional output energize instruction
(Figure 4.7) causes the output instruction to remain energized
continuously. This may not be desirable in output device
programming.
Figure 4.6
Output Energize Instruction
||
06
()
15
112
012
Figure 4.7
Unconditional Output Energize Instruction
()
15
035
Output Latch and Unlatch Instructions
There are two output instructions that are termed retentive. These
instructions are:
Output Latch –(L)–
Output Unlatch –(U)–
These instructions are usually used as a pair for any bit address they
control.
The Output Latch instruction is somewhat similar to the Output Energize
instruction. The Output Latch instruction tells the processor to set an
addressed memory bit on when rung conditions are true. Unlike the Output
Energize instruction, the Output Latch instruction is retentive. This means
that once the rung conditions go false, the latched bit remains on until reset
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