Background Execution - Omron CS1G/H-CPUxx-EV1 Programming Manual

Cycle Time/High-speed Processing

6-1-10 Background Execution

Applications
Procedure
1,2,3...
266
The equation for maximum data link I/O response time is as follows:
Input ON delay
Cycle time of PLC at CPU Unit #1 × 1.5
Communications cycle time × 2
Cycle time of PLC at CPU Unit #2 × 1
Output ON delay
Total (data link I/O response time)
Background execution can be used to reduce fluctuations in the cycle time.
Background execution is supported only by CS1-H, CJ1-H, or CJ1M CPU
Units, or CS1D CPU Units for Single-CPU Systems.
Table data processing (such as data searches) and text string processing
(such as text string searches), require time to execute, and can create large
fluctuations in the cycle time due to the extended amount of time required to
execute them.
With the CS1-H, CJ1-H, or CJ1M CPU Units, or CS1D CPU Units for Single-
CPU Systems (See note.), however, background execution (time slicing) can
be used to execute the following instructions over several cycles to help con-
trol fluctuations in the cycle time. The PLC Setup enables setting background
execution for each type of instruction.
Note The CS1D CPU Units for Duplex-CPU Systems do not support background
execution.
• Table data processing instructions
• Text string processing instructions
• Data shift instructions (ASYNCHRONOUS SHIFT REGISTER only)
Setting background execution for the above instructions can help control tem-
porary increases in the cycle time.
CS1 CPU Unit
MAX
Long execution
time
Longer cycle time
when MAX is
executed.
Background execution can be used for large quantities of data processing,
such as data compilation or processing, that is required only at special times
(e.g., once a day) when reducing the effect on the cycle time is more impor-
tant than the speed of the data processing.
1. Set the PLC Setup to enable background execution for the required in-
structions.
2. Set the communications port number (logical port number) to be used for
background execution in the PLC Setup. This port number will be used for
all instructions processed in the background.
1.5 ms
25 ms × 1.5
10 ms × 2
20 ms × 1
15 ms
94 ms
CS1-H or CJ1-H
CPU Unit
MAX
Execution
only
started.
↓
Section 6-1
---
Faster by 12.5 ms
(25 ms x 0.5)
---
Faster by 20 ms
(20 ms x 1)
---
Faster by 32.5 ms (26%
faster)
Background
execution
Executed over
several cycles
using time slicing.