Allocating Network Bandwidth - Omron DEVICENET SAFETY - CONFIGURATION MANUAL 05-2005 System Configuration Manual

3-2-2

Allocating Network Bandwidth

The average EPIs for safety I/O communications and standard I/O communications are calculated by enter-
ing the network bandwidth usage rate for each into the Network Configurator.
Calculate the EPIs using the following procedures:
1. Set the virtual network on the Network Configurator as needed.
2. Click the EPI Calculation Button in the lower portion of the Network Configuration Pane.
3. Input the network bandwidth used in safety I/O communications and the bandwidth used in standard I/O
communications, and then click the Calculate Button.
4. The average EPI of all the connections in the safety I/O communications and the communications cycle
time in the standard I/O communications will be displayed for each baud rate. Review the EPIs for safety
I/O communications and the communications cycle time of the Standard Master referring to the baud rate
that is to be used.
IMPORTANT: • Keep 10% or more space in the network bandwidth for establishing a connection and for
Note: – If you do not want to mix with standard I/O communications, set the network bandwidth used for
standard connections to 0.
– The EPI is set in 1 ms increments. The network bandwidth to be used may thus be smaller than the
allocated value when the calculated value is used.
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communications of the Network Configurator. If the user application uses explicit message
communications, additional network bandwidth is necessary. In this case, decide the net-
work bandwidth for the explicit messaging in consideration of the amount of the data and
the frequency of the communications.
• The calculation result is the average value of all the safety connections. Use this value as
a guideline. Adjust the EPI for the whole network by shortening the EPI for connections
that require a high-speed reaction time and lengthening the EPI for connections that do
not require high speed.
• Check that the displayed usage rate in the lower portion of the Network Configuration
Pane is the allocated value or less when adjusting the EPI of the whole network based on
the calculation results. Communications timeout might occur if the calculated bandwidth is
not properly allocated to the standard connections because the priority of safety I/O com-
munications is higher than that of standard I/O communications.
• The total network bandwidth used in the safety connections and the standard connections
must be around 90% at the maximum, i.e., 10% or more available bandwidth must be left
for explicit message communications.
• Perform user testing to make sure that there is no problem in the set values.
Section 3: Constructing a Safety Network