4.1 User Program Types and Execution Timing
4.1.1 Ladder Programs
4-4
Hierarchical Configuration
There are four types of ladder drawings: parent drawings, child drawings, grandchild drawings,
and operation error drawings.
• Parent Drawings
These drawings are automatically executed by the system program when the execution con-
ditions are met.
• Child Drawings
These drawings are executed when they are called from a parent drawing with a SEE instruc-
tion.
• Grandchild Drawings
These drawings are executed when they are called from a child drawing with a SEE instruc-
tion.
• Operation Error Drawings
These drawings are automatically executed by the system program when an operation error
occurs.
A parent drawing cannot call a child drawing from a different type of drawing. Similarly, a child
drawing cannot call a grandchild drawing from a different type of drawing. A parent drawing
cannot call a grandchild drawing directly. The parent drawing first must call the child drawing,
and then the child drawing must call the grandchild drawing. This is called the hierarchical con-
figuration of drawings.
The following figure shows the parent-child-grandchild structure in which a program is created.
User Functions
Grandchild
Drawings
Child
Drawings
Parent
Drawing
Note 1: = A, I, H, or L
DWG. DWG.01
DWG.nn
DWG.01.01
DWG.01.02
FUNC-001
FUNC-006
FUNC-032
FUNC-064
DWG.01.03
DWG notation:
Grandchild drawing number
Parent drawing type (A, I, H, or L)
Child drawing number
Note 2: The following notation is used for operation error drawings.
Parent drawing type (A, I, H, or L) of the
drawing where the error occurs
Fixed value (00)
DWG.
.
DWG. 00
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