Filter
Top Products
296
Message Service Transmission Delay Section 10-5
CPU Bus Unit Service
Processing Time (Remote
Node)
The following table shows the CPU Bus Unit service processing time, which
depends on the CPU Unit’s CPU processing mode setting.
Note CJ2 CPU Units support only Normal Mode.
For details, refer to the CPU Unit’s Operation Manual.
Note Depending on the actual operating environment, the transmission time may
be longer than the one calculated with the equations given here. The following
factors can cause longer transmission times: other traffic on the network, win-
dow sizes of network nodes, other traffic at the EtherNet/IP Unit or built-in Eth-
erNet/IP port itself (e.g., simultaneous tag data link communications), and the
system configuration.
Example Calculation In this example, SEND(090) is used to send 256 words of data between two
PLCs. The maximum transmission delay is calculated based on the following
operating conditions.
• Local node’s CPU cycle time: 10 ms
• Local node’s CPU execution mode: Normal
• Local node’s CPU peripheral servicing time: Default (4%)
• Remote node’s CPU cycle time: 5 ms
• Remote node’s CPU execution mode: Normal
• Remote node’s CPU peripheral servicing time: Default (4%)
• Baud rate: 100Base-TX
CPU execution mode Processing time details
Normal Mode (See note.) Set peripheral servicing time
Default: 4% of CPU Unit cycle time
(10% for CJ2 CPU Units)
Priority peripheral servicing EtherNet/IP Unit or
built-in EtherNet/IP
port is given prior-
ity.
Time slice peripheral servicing
execution time
EtherNet/IP Unit or
built-in EtherNet/IP
port 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
(10% for CJ2 CPU Units)
Parallel processing with asyn-
chronous memory access
1 ms max.
Item Calculated value
CPU Bus Unit service cycle (local
node)
10 ms
CPU Bus Unit service processing
time (local node)
0.4 ms
Send processing (256 × 0.002) + 0.550 = 1.062 ≅ 1.1 ms
Transmission delay (256 × 0.0013) + 0.0118 = 0.3446 ≅ 0.3 ms
Receive processing (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
Maximum transmission delay 10 + 0.4 + 1.1 + 0.3 + 1.5 + 5 + 0.2 = 18.5 ms