Rockwell Automation 57C409 2 Channel Analog Input Module - Manual (Page 20)

4Ć4
4.2 Configuration
Before any application programs can be written, it is necessary to
configure, or set, the definitions of systemĆwide variables, i.e. those
that must be globally accessible to all tasks.
For DCS 5000 andAutoMax Version 2.1 andearlier, you define
systemĆwide variables by writing a Configuration task. For AutoMax
Version 3.0 and later, you define systemĆwide variables using the
AutoMax Programming Executive. After these variables are defined,
you can generate the configuration file automatically, which
eliminates the requirement to write a configuration task for the rack. If
you are using AutoMax Version 2.1 or earlier, refer to Appendix E for
example that show how to define variables in the configuration task. If
you are using AutoMax Version 3.0 or later, see the AutoMax
Programming Executive (JĆ3750) for information about configuring
variables.
4.3 Reading And Writing Data In Application
Tasks
In order for an input module to be referenced by application
software, it is first necessary to assign symbolic names to the
physical hardware. In AutoMax Version 2.1 and earlier, this is
accomplishedby IODEF statements in the configuration task. See
Appendix E for an example. In AutoMax version 3.0 and later, you
assign symbolic names using the Programming Executive.
Each application program that references the symbolic names
assigned to the input module in configuration must declare those
names COMMON.
The frequency with which tasks, or application programs, readtheir
inputs and write their outputs depends on the language being used.
Ladder logic and control block tasks read inputs once at the
beginning of each scan andwrite outputs once at the endof scan.
BASIC tasks readan input andwrite an output for each reference
throughout the scan.