Specifications

2-2

2.1 What is a Hierarchical Sequence Program?

The hierarchy is to create a sequence program by dividing control functions performed in a

programmable controller CPU into a number of levels.

In higher levels, the processing order and timing in a fixed range is controlled.

With each move from a higher level to a lower level, control content and processes are

progressively subdivided within a fixed range, and specific processes are described in lower

levels.

In the Structured project, hierarchical sequence programs are created with the configuration that

states the highest level as the project, followed by program files, tasks, and POUs (abbreviation

for Program Organization Units).

Project

POUs

Task (Initialization)

Initial process

Lamp test

Program file (Operation preparation)

Task (Station A control)

Conveyor drive A

Data process A

Program file (Station A)

Task (Station B control)

Task (Indicator control)

Conveyor drive B

Data

process B

Indicator output