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4-4-4 OUTPUT and OUTPUT NOT
The simplest way to output the results of combining execution conditions is to
output it directly with the OUTPUT and OUTPUT NOT. These instructions are
used to control the status of the designated operand bit according to the execu-
tion condition. With the OUTPUT instruction, the operand bit will be turned ON
as long as the execution condition is ON and will be turned OFF as long as the
execution condition is OFF. With the OUTPUT NOT instruction, the operand bit
will be turned ON as long as the execution condition is OFF and turned OFF as
long as the execution condition is ON. These appear as shown below. In mne-
monic code, each of these instructions requires one line.
00000
00201
00200
00001
Address Instruction Operands
00000 LD 00000
00001 OUT 00200
Address Instruction Operands
00000 LD 00001
00001 OUT NOT 00201
In the above examples, IR 00200 will be ON as long as IR 00000 is ON and IR
00201 will be OFF as long as IR 00001 is ON. Here, IR 00000 and IR 00001 will
be input bits and IR 00200 and IR 00201 output bits assigned to the Units con-
trolled by the PC, i.e., the signals coming in through the input points assigned IR
00000 and IR 00001 are controlling the output points assigned IR 00200 and IR
00201, respectively.
The length of time that a bit is ON or OFF can be controlled by combining the
OUTPUT or OUTPUT NOT instruction with TIMER instructions. Refer to Exam-
ples under 5-14-1 TIMER – TIM for details.
4-4-5 The END Instruction
The last instruction required to complete a simple program is the END instruc-
tion. When the CPU Unit cycles the program, it executes all instruction up to the
first END instruction before returning to the beginning of the program and begin-
ning execution again. Although an END instruction can be placed at any point in
a program, which is sometimes done when debugging, no instructions past the
first END instruction will be executed until it is removed. The number following
the END instruction in the mnemonic code is its function code, which is used
when inputted most instruction into the PC. These are described later. The END
instruction requires no operands and no conditions can be placed on the same
instruction line with it.
Instruction
00000 00001
END(01)
Program execution
ends here.
Address Instruction Operands
00000 LD 00000
00001 AND NOT 00001
00002 Instruction
00003 END(01) ---
If there is no END instruction anywhere in the program, the program will not be
executed at all.
Basic Ladder Diagrams Section 4-4