Rockwell Automation 1336T Function Block Prog. Manual, Series A/B - Manual (Page 42)

2–8 System Component Detail
1336 FORCE — 5.9 August 1995
While you are creating your execution list, you are generally
working on a terminal using DriveTools, a PLC, or a GPT. At this
point, the execution list is an array of words that the software you are
using can understand. You need to download and compile your
execution list before the drive can execute it.
The download process sends a copy of the execution list array from
the terminal to the drive. The compile process uses the execution list
in the drive to create an application which contains the functionality
and data within the drive. The drive can then execute the application.
The process that takes place when you download and compile your
execution list is as follows:
1. The terminal device (DriveBlockEditor, GPT, or PLC) writes or
downloads a new execution list.
2. The drive software checks the execution list for errors.
3. After the initial service checks have been completed
satisfactorily, the drive acknowledges the download service and
prepares the execution list to compile as a background task.
4. The drive disables any currently active (executing) function block
application and calls the function block compiler.
5. The compiler moves sequentially through the execution list
creating and initializing the function block objects. A function
block event object associates a certain functional operation to be
performed with the appropriate information and data.
6. All links associated with the function blocks are processed.
7. If no errors are encountered, the drive begins executing the
application.
When the drive enables a function block application, the events are
executed every 20 milliseconds, regardless of how long it actually
takes to execute the application. For example, if it takes the
processor 5 milliseconds to execute your application, the drive’s
processor does not start to execute the application again until the full
20 milliseconds have elapsed. This is referred to as a 20 millisecond
task interval.
Refer to Chapter 3 for more information about the compile process.
Chapter 5 provides more information on the PLC block transfer
service for the download and compile operation.
Downloading and
Compiling the Execution
List