5-2-8 Processing Performed in and Execution Timing of the Tag Data Link Service ......................... 5-26
5-2-9 Processing Performed in and Execution Timing of the System Services ................................. 5-29
5-2-10 Assigning I/O Refreshing to Tasks............................................................................................ 5-31
5-2-11 Assigning Tasks to Programs ................................................................................................... 5-32
5-2-12 Parameters for Primary Periodic Task and Periodic Tasks ....................................................... 5-33
5-2-13 Ensuring Concurrency of Variable Values between Tasks........................................................ 5-35
5-2-14 Variable Access from Outside the Controller ............................................................................ 5-39
5-2-15 Instructions Related to Tasks.................................................................................................... 5-42
5-2-16 System-defined Variables Related to Tasks ............................................................................. 5-43
5-2-17 Errors Related to Tasks ............................................................................................................ 5-45
5-2-18 Monitoring Task Execution Status and Task Execution Times.................................................. 5-47
5-3 Task Design Methods and I/O Response Times ................................................................. 5-51
5-3-1 Checking the Task Execution Time...........................................................................................5-51
5-3-2 Checking the System Service Monitoring Settings................................................................... 5-53
5-3-3 Examples of Task Design ......................................................................................................... 5-53
5-3-4 System Input and Output Response Times .............................................................................. 5-54
Section 6 Programming
6-1 Overview of Programming Procedures ................................................................................. 6-3
6-2 POUs (Program Organization Units)...................................................................................... 6-5
6-2-1 What Are POUs? ........................................................................................................................ 6-5
6-2-2 Overview of the Three Types of POUs ....................................................................................... 6-6
6-2-3 Differences between Programs, Functions, and Function Blocks............................................... 6-7
6-2-4 Details on Programs ................................................................................................................... 6-7
6-2-5 Details on Function Blocks ......................................................................................................... 6-8
6-2-6 Details on Functions ................................................................................................................. 6-17
6-2-7 Operation That Applies to Both Functions and Function Blocks............................................... 6-22
6-2-8 POU Restrictions ...................................................................................................................... 6-24
6-3 Variables ................................................................................................................................. 6-27
6-3-1 Variables................................................................................................................................... 6-27
6-3-2 Types of Variables..................................................................................................................... 6-27
6-3-3 Types of User-defined Variables in Respect to POUs .............................................................. 6-28
6-3-4 Attributes of Variables............................................................................................................... 6-29
6-3-5 Data Types................................................................................................................................ 6-30
6-3-6 Derivative Data Types............................................................................................................... 6-39
6-3-7 Array Specifications and Range Specifications for Data Types ................................................ 6-49
6-3-8 Variable Attributes..................................................................................................................... 6-54
6-3-9 Changes to Variables for Status Changes................................................................................ 6-62
6-3-10 Function Block Instances.......................................................................................................... 6-64
6-3-11 Monitoring Variable Values ....................................................................................................... 6-64
6-3-12 Restrictions on Variable Names and Other Program-related Names ....................................... 6-65
6-4 Constants (Literals)............................................................................................................... 6-67
6-4-1 Constants.................................................................................................................................. 6-67
6-4-2 Types of Constants ................................................................................................................... 6-67
6-5 Programming Languages ..................................................................................................... 6-72
6-5-1 Programming Languages ......................................................................................................... 6-72
6-5-2 Ladder Diagram Language ....................................................................................................... 6-72
6-5-3 Structured Text Language......................................................................................................... 6-78
6-6 Instructions .......................................................................................................................... 6-112
6-6-1 Instructions ............................................................................................................................. 6-112
6-6-2 Basic Understanding of Instructions ....................................................................................... 6-112
6-6-3 Instruction Errors .................................................................................................................... 6-115
6-7 Namespaces......................................................................................................................... 6-120
6-7-1 Namespaces........................................................................................................................... 6-120
6-7-2 Namespace Specifications ..................................................................................................... 6-121
6-7-3 Procedure for Using Namespaces.......................................................................................... 6-124
6-8 Libraries ............................................................................................................................... 6-125
6-8-1 Introduction to Libraries .......................................................................................................... 6-125