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Communicating between OMRON PLCs Section 6-6
CPU Bus Unit Service Processing Time (Remote Node)
The processing time will be as follows, depending on the CPU processing
mode settings at the CPU Unit.
For details, refer to the CPU Unit operation manual.
Note The actual operating environment can cause transmission delays larger than
those calculated with the methods given here. Among the causes of longer
delays are the following: traffic on the network, window sizes at network
nodes, traffic through the Ethernet Unit (e.g., socket servicing, FTP server
communications, etc.), and the system configuration.
Example Calculations
The following example shows calculations for sending 256 words between two
PLC nodes using SEND(090). Calculations are shown in the following table.
Conditions
Local node CPU cycle time: 10 ms
Local node CPU execution mode: Normal
Local node CPU uniform peripheral servicing time: Default (4%)
Remote node CPU cycle time: 5 ms
Remote node CPU execution mode: Normal
Remote node CPU peripheral servicing time: Default (4%)
Baud rate: 100Base-TX
CPU processing mode
settings
Processing time considerations
Normal Mode Set peripheral servicing time
Default: 4% of CPU Unit cycle time
Priority peripheral servicing Ethernet Unit is given
priority.
Time slice peripheral servicing
execution time
Ethernet Unit is not
given priority.
Set peripheral servicing time
(Default: 4% of CPU Unit cycle
time)
Parallel processing with syn-
chronous memory access
Set peripheral servicing time
(Default: 4% of CPU Unit cycle time)
Parallel processing with
asynchronous memory
access
1 ms max.
Item Calculation
CPU Bus Unit service cycle (local node) 10 ms
CPU Bus Unit service processing time
(local node)
0.4 ms
Transmission processing time 256 × 0.002 + 0.550 = 1.062 ≈ 1.1 ms
Transmission delay 256 × 0.0013 + 0.0118 = 0.3446 ≈
0.3 ms
Reception processing time 256 × 0.003 + 0.704 = 1.472 ≈ 1.5 ms
CPU Bus Unit service cycle (remote node) 5 ms
CPU Bus Unit service processing time
(remote node)
0.2 ms
Total 10 + 0.4 + 1.1 + 0.3 + 1.5 + 5 + 0.2 =
18.5 ms
