Task Design Methods And I/O Response Times; Checking The Task Execution Time - Omron NJ-series User Manual

5-3 Task Design Methods and I/O
Response Times
This section provides information on estimating task execution times, information on confirming system
service monitoring settings, an example of task designing, and information on I/O response times.
The primary periodic task and periodic tasks of an NJ-series Controller operate according to the speci-
fied task periods. If the actual execution time exceeds the task period, an error occurs.
This section uses an example that consists of one primary periodic task to describe estimation and
appraisal methods.
Precautions for Safe Use
The task execution times in the physical Controller depends on the logic operations that are per-
formed in the user program, the presence of communications commands and data links, on
whether data tracing is performed, and on other factors. Before starting actual operation, you
must test performance under all foreseeable conditions on the actual system and make sure that
the task periods are not exceeded and that suitable communications performance is achieved.
5-3-1

Checking the Task Execution Time

Always design your system so that the average and maximum task execution times that are esti-
mated with the methods that are described in this section sufficiently fit within the specified task peri-
ods.
 Desktop Calculations
First, refer to A-2 Calculating Guidelines for the Real Processing Times of Tasks to make a rough
estimate of the average task execution time on paper. You cannot estimate the maximum value on
paper.
 Estimating with the Simulator on the Sysmac Studio
Use the Task Execution Time Monitor of the Simulator on the Sysmac Studio to estimate the aver-
age and maximum task execution times. Use the following procedure to check operation on the Sim-
ulator.
1
Create the Unit and slave configurations, create the global variables and device variables, and
create the axes (to create the Axis Variables).
2
Create the programs to check.
3
Set up the tasks and build the project.
4
Start the Simulator in Execution Time Estimation Mode.
5
Set the Expanded number of I/O points in the CJ-series Unit parameters in the Task Execution
Time Monitor to create user-defined variables for specified CJ-series Special Units. Also set the
sizes of the expansion areas (e.g., fixed I/O allocation areas for the DeviceNet Unit) for AT spec-
ifications (i.e., the number of output words and the number of input words). These sizes are
used to calculate the I/O refresh time for the specific Special Units.
6
Estimate the task execution times in the Task Execution Time Monitor.
NJ-series CPU Unit Software User's Manual (W501)
5 Designing Tasks
5-51
5