Omron DeviceNet Safety, Руководство по настройке системы

Страница: 53 / 376

19
Allocating Network Bandwidth Usage and Calculating the Best EPI Section 2-2
2-2 Allocating Network Bandwidth Usage and Calculating the
Best EPI
Almost all of the DeviceNet network bandwidth can be used for safety I/O and
standard I/O communications.
Communications may time out, however, if the connection settings exceed the
acceptable bandwidth usage for each type of communications.
Check the connection settings and, if a setting is found to exceed the accept-
able bandwidth usage rate, the setting must be changed to the value outlined
in the following table.
The network configuration may need to be changed if the settings exceed the
acceptable bandwidth usage rate as a result of securing the required commu-
nications performance (i.e., the required network reaction time for safety I/O
communications).
This section describes how to check the network bandwidth used for safety
I/O communications in the designed network, how to calculate the best EPI
from the set bandwidth usage rate, and how to re-set the value.
2-2-1 Checking the Network Bandwidth Used for Safety I/O
Communications
The actual network bandwidth usage rate for safety I/O communications for
the connections set in the virtual network is displayed at the bottom of the
Network Configuration Window unde
r Usage of Network Bandwidth for Safety
Connections. The network bandwidth usage rate is displayed for each baud
rate, as shown in the following diagram.
As shown in the diagram, the faster the baud rate, the lower the bandwidth
usage rate.
IMPORTANT Keep 10% or more of the network bandwidth available for establishing con-
nections and for explicit message communications with the Network Configu-
rator, whether using only safety I/O communications or using both safety I/O
and standard I/O communications.
Even if 10% or more is available, however, safety or standard communications
might time out, depending on the Network Configurator operation (e.g., moni-
toring or other operations that create a load on the network) or if the user
• Safety I/O
communications
EPI (Expected Packet Interval) setting for safety connections
• Standard I/O
communications
Master communications cycle time
When a virtual network (including program-
ming) is created, the network bandwidth us-
age conditions of safety connections at
each baud rate are displayed.