Specifications

Programming Using programmable controllers
MELSEC-L Series Quick start guide 2 - 11
2.6 Programming
This section explains how to create a program (sequence program) for sequence control.
2.6.1 "Devices" and "Instruction symbols" in programming
Combine "Devices" and "Instruction symbols" to create a sequence program.
Devices
Devices include bit devices and word devices.
● Bit device: Handles one-bit information such as the ON/OFF of a switch or a lamp.
● Word device: Handles 16-bit information such as numeric values and character strings.
Fig. 2-8:
Examples of bit devices
LS70001
Device name Device symbol Description
Input X Receives a signal from an external device such as a switch.
Output Y Outputs a signal to an external device such as a lamp.
Internal relay M Temporarily saves data status in programs.
Timer (contact) T
Used to measure time.
(When the set time comes, the contact is set to ON.)
Counter (contact) C
Used to count the number of times the input condition turns from OFF to ON.
(When the counter reaches the set number, the contact is set to ON.)
Tab. 2-3: Description of bit devices
Fig. 2-9:
Examples of word devices
Device name Device symbol Description
Data register D Registers numeric values and character strings.
Timer
(current value)
T
Used to measure time.
(Stores the current value of measuring time.)
Counter
(current value)
C
Used to count the number of times the input condition turns from OFF to ON.
(Stores the current value of the counter.)
Tab. 2-4: Description of word devices
TERMINOLOGY Device A location to store data such as ON/OFF, numeric values, and char-
acter strings in the programmable controller.
Internal relay Breaks/connects the sequential circuit by switching ON/OFF.
Contact An input used when creating a sequence program.
ON/OFF of a switch ON/OFF of a lamp
Numeric value Character string
123456789 abcedefg