Allen-Bradley 2080-LC20-20AWB, User Manual

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Rockwell Automation Publication 2080-UM005E-EN-E - March 2018 73
Chapter
6
Program Execution in Micro800
This section provides a brief overview of running or executing programs with a
Micro800 controller.
For detailed information regarding ladder diagrams, instructions, function blocks
and so on, see the Micro800 Programmable Controllers Instruction Manual,
publication 2080-RM001 .
Overview of Program
Execution
A Micro800 cycle or scan consists of reading inputs, executing programs in
sequential order, updating outputs and performing housekeeping (data log,
recipe, communications).
Program names must begin with a letter or underscore, followed by up to 127
letters, digits or single underscores. Use programming languages such as ladder
logic, function block diagrams and structured text.
Up to 256 programs may be included in a project, depending on available
controller memory. By default, the programs are cyclic (executed once per cycle or
scan). As each new program is added to a project, it is assigned the next
consecutive order number. When you start up the Project Organizer in
Connected Components Workbench, it displays the program icons based on this
order. You can view and modify an order number for a program from the
program’s properties. However, the Project Organizer does not show the new
order until the next time the project is opened.
The Micro800 controller supports jumps within a program. Call a subroutine of
code within a program by encapsulating that code as a User Defined Function
(UDF) or User Defined Function Block (UDFB). A UDF is similar to a
traditional subroutine and uses less memory than a UDFB, while a UDFB can
have multiple instances. Although a UDFB can be executed within another
UDFB, a maximum nesting depth of five is supported. A compilation error
occurs if this is exceeded. This also applies to UDFs.
Alternatively, you can assign a program to an available interrupt and have it
executed only when the interrupt is triggered. A program assigned to the User
Fault Routine runs once just prior to the controller going into Fault mode.
IMPORTANT
This section generally describes program execution in Micro800
controllers. Certain elements may not be applicable or true in certain
models (for example, Micro820 does not support PTO motion control).