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3 CONFIGURATION OF INSTRUCTIONS
3. CONFIGURATION OF INSTRUCTIONS
3.1 Configuration of Instructions
Most CPU module instructions consist of an instruction part and a device part.
• Instruction part.....Indicates the function of the instruction
• Device part ..........Indicates the data that is to be used with the instruction.
The device part is classified into source data, destination data, and number of devices.
3
(1) Source
(a) Source is the data used for operations.
(b) The following source types are available, depending on the designated device:
(2) Destination
(a) The destination stores the data after the operation has been conducted.
However, some instructions require storing the data to be used in an operation at the
destination prior to the operation execution.
Example: An addition instruction involving BIN 16-bit data
(b) A device for the data storage must always be set to the destination.
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S
• Constants .....................................Designates the numeric value to be used in the
• Bit devices and Word devices .....Designates the device that stores the data to be
D
+
S
D
Stores the data needed for operation
prior to the actual operation.
operation.
This is set when the program is written, and cannot
be changed during the execution of the program.
Constants should be indexed when using them as
variable data.
used for the operation.
Data must be stored in the designated device until
when the operation is executed.
By changing the data stored in a designated device
during program execution, the data to be used in
the instruction can be changed.
+
D
S1
S2
Stores only the operation results.
MELSEC-Q/QnA
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