4.1 User Program Types and Execution Timing4.1.1 Ladder Programs4-34 Creating User Programs4.1 User Program Types and Execution TimingThere are three types of user programs:• Ladder programs• Motion programs• Sequence programsThis section describes these programs.4.1.1 Ladder ProgramsLadder 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 ConfigurationThis section describes the types of ladder drawings and their hierarchical configuration. TypesLadder 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 executedbefore 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 inputfrom 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 aswell as for standard I/O control.The following table lists the priority, execution conditions, and maximum number of drawingsfor each type of ladder drawing.* Drawings with lower numbers have higher priority.Drawing Type Priority* Execution Condition Maximum Number ofDrawingsDWG.A (Startup Drawings) 1 Power ON (These drawings are executedonce when the power supply is turned ON.) 64DWG.I (Interrupt Drawings) 2External interrupt (These drawings are exe-cuted when a DI interrupt or counter matchinterrupt is received from an Option Mod-ule.)64DWG.H (High-speed ScanProcess Drawings) 3 Started at fixed intervals. (These drawingsare executed once every high-speed scan.) 1,000DWG.L (Low-speed ScanProcess Drawings) 4 Started at fixed intervals. (These drawingsare executed once every low-speed scan.) 2,000
