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7 OPERATION CONTROL PROGRAMS
(3) Structure of instruction
Many of the instructions usable in operation control programs can be divided into
instruction and data parts.
The instruction and data parts are used for the following purposes.
• Instruction part.......... Indicates the function of that instruction.
• Data part................... Indicates the data used in the instruction.
"Substitution: =" structure example
D0 = #0
Data part: Source (S)
Instruction part
Data part: Destination (D)
(a) Source (S)
1) The source is the data used in an operation.
2) It varies with the device specified in each instruction is shown below.
• Bit or word device
Specify the device which stores the data used in operation.
The data must have been stored in the specified device until the
operation is executed.
Changing the data stored in the specified device during program
execution allows changing the data used in that instruction.
• Constant
Specify the numerical value used in an operation.
As the constant is set during program creation, it cannot be changed
during program running.
(b) Destination (D)
1) As the destination data, after-operation data is stored.
2) Destination data is always set the device for storing the data.