Справочник Пользователя для Mitsubishi Electronics 700 Series

The built-in PLC function has two different programming methods: one that uses
ladders and the other that uses dedicated instructions.
• Programming that uses ladders is performed in the relay symbolic language. *1
• Programming that uses dedicated instructions is performed in the logic symbolic

language. *2

Whether the relay symbolic language or logic symbolic language is used, the same
program is created. 
 

The relay symbolic language is based on the concept of a relay control circuit.
You can perform programming in the representation close to the sequence circuit of
relay control.
(1) Ladder block

A ladder block is the minimum unit for performing sequence program operation. It
starts with the left hand side vertical bus and ends with the right hand side vertical
bus.

Fig 3.2 Ladder Blocks

*1. When using GX Developer for programming, perform programming in the "ladder mode".
*2. When using GX Developer for programming, perform programming in the "list mode".

Right hand 
side vertical 
bus

Ladder 
blocks

Left hand side vertical bus

Step number

* X0 to X5: Indicate inputs.
  Y10 to Y14: Indicate outputs.