Cautions On Creation Of Fundamental Programs; Programming Procedure And Execution Order - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
6.2

Cautions on Creation of Fundamental Programs

This section explains cautions on programming.
6.2.1

Programming procedure and execution order

1. Contact configuration and steps
Even for a sequence circuit offering a same operation, the program can be simplified and the number of steps
can be saved depending on the contact configuration method.
1) It is recommended to write a circuit with many serial contacts in an upper position.
(1)LD
(2)LD (3)AND
2) It is recommended to write a circuit with many parallel contacts in a left position.
(1)LD
(4)ANB
2. Program execution and programming order
A sequence program is executed "from top to bottom" and "from left to right".
Code the sequence instruction list according to this rule.
(1)
(2)
174
(5)OUT
(4)ORB
(2)LD
(5)OUT
(3)OR
(5)
(3)
(6)
(4)
(8)
6 What to Understand before Programming
6.2 Cautions on Creation of Fundamental Programs
(1)LD (2)AND
(3)OR
ORB instruction is not necessary
(1)LD (3)AND
(2)OR
ANB instruction is not necessary
(7) (9) (10)
(11)
(4)OUT
(4)OUT
Executed