4.1 User Program Types and Execution Timing
4.1.1 Ladder Programs
4-3
4
Creating User Programs
4.1
User Program Types and Execution Timing
There are three types of user programs:
•
Ladder programs
•
Motion programs
•
Sequence programs
This section describes these programs.
4.1.1
Ladder Programs
Ladder programs are managed as drawings (ladder diagrams) that are identified by their draw-
ing numbers (DWG numbers). The ladder drawings form the basis of the ladder programs.
Drawing Types and Hierarchical Configuration
This section describes the types of ladder drawings and their hierarchical configuration.
Types
Ladder drawings are divided into four different types based on their purpose.
•
DWG.A (Startup Drawings)
This type of ladder drawing is used to set register data. These ladder drawings are executed
before high-speed scan process drawings and low-speed scan process drawings.
•
DWG.I (Interrupt Drawings)
This type of ladder drawing is used to perform processing with priority given to signals input
from an Optional Module. These ladder drawings are executed with higher priority than high-
speed scan process drawings regardless of the scan cycle.
•
DWG.H (High-speed Scan Process Drawings)
This type of ladder drawing is used to perform motion control or high-speed I/O control.
•
DWG.L (Low-speed Scan Process Drawings)
This type of ladder drawing is used for communications with HMIs and external devices as
well as for standard I/O control.
The following table lists the priority, execution conditions, and maximum number of drawings
for each type of ladder drawing.
*
Drawings with lower numbers have higher priority.
Drawing Type
Priority*
Execution Condition
Maximum Number of
Drawings
DWG.A (Startup Drawings)
1
Power ON (These drawings are executed
once when the power supply is turned ON.)
64
DWG.I (Interrupt Drawings)
2
External interrupt (These drawings are exe-
cuted when a DI interrupt or counter match
interrupt is received from an Option Mod-
ule.)
64
DWG.H (High-speed Scan
Process Drawings)
3
Started at fixed intervals. (These drawings
are executed once every high-speed scan.)
1,000
DWG.L (Low-speed Scan
Process Drawings)
4
Started at fixed intervals. (These drawings
are executed once every low-speed scan.)
2,000