49
Basic Concepts Section 2-1
3. An input bit must always be inserted before and never after an output in-
struction like an output bit. If it is inserted after an output instruction, then
a location error will occur during a Programming Device program check.
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.
0002
01
0000
00
0000
03
0000
04
0000
01
0002
01
0000
00
0000
00
(Output bit)
(Output bit)
0000
00
(Input bit)
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