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Programming Concepts Section 1-1
4. The same output bit cannot be programmed in an output instruction more
than once. Instructions in a ladder program are executed in order from the
top rung in a single cycle, so the result of output instruction in the lower
rungs will be ultimately reflected in the output bit and the results of any pre-
vious instructions controlling the same bit will be overwritten and not out-
put.
5. An input bit cannot be used in an OUTPUT instruction (OUT).
6. An END(001) instruction must be inserted at the end of the program in
each task.
• If a program without an END(001) instruction starts running, a program
error indicating No End Instruction will occur, the ERR/ALM LED on the
front of the CPU Unit will light, and the program will not be executed.
• If a program has more than one END(001) instruction, then the program
will only run until the first END(001) instruction.
• Debugging programs will run much smoother if an END(001) instruction is
inserted at various break points between sequence rungs and the
END(001) instruction in the middle is deleted after the program is
checked.
100.00
100.00
(Output bit)
(Output bit)
0.00
(Input bit)
000000
000001
000000
000001
000000
000001
000000
000001
000000
000001
000000
000001
END
END
END
END
END
END
END
END
Task (program)
Task (program)
Task (program)
Task (program)
Task (program)
Task (program)
Will not be executed.
Will not be executed.
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