Mitsubishi Electronics 13JW55 ユーザーズマニュアル

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The internal sequential operation can be regarded as the program of

the programmable controller. The program is saved in the program

memory as similar to the instruction list

Step number

Instruction

word

Device

0 LD X6

1 OR

Y74

2 ANI T1

3 OUT

Y74

4 LD

Y74

5 ANI X6

6 OUT

K30

Y74

K30

END

10 END

Repeat
operation

(a) Ladder diagram

(b) Instruction list (program list)

Figure 1.2 Program

• A program consists of a large number of instruction words and

devices.

• The instructions contain instruction words and devices. In addition,

the instructions are numbered to represent the order of operations.

The numbers are called step numbers.

(Instruction words are also called instructions.)

• The number of steps varies depending on the types of instructions

or the setting method for the values to be used for the I/O numbers

and operations. (The more steps are needed for the operation with

complicated operation.)

• The instructions repeat from the step number 0 to the END

instruction. (This is called "repeat operation", "cyclic operation" or

"scanning".)

Amount of time necessary for one cycle is called operation cycle

(scan time).

• The number of steps from the step number 0 to the END instruction

is the length or size of the program.

• The program is stored in the program memory inside the CPU. The

operation is executed in a ladder block unit.

One ladder block ranges from the operation start instruction (LD,

LDI) to the OUT instruction (including the data instruction).