Omron NX102 series

6-13
6 Process Data Communications and SDO Communications
NJ/NX-series CPU Unit Built-in EtherCAT Port User’s Manual (W505)
6-1 Process Data Communications (PDO Communications)
6
6-1-4 System Response Time in Process Data Communications
Precautions for Correct UsePrecautions for Correct Use
The values that are found in the above formula are guidelines instead of guaranteed values. You
must use a physical device to check the performance before the actual operation.
The following describes how to find each element value in the formula.
 Task Period of Periodic Task
This indicates the task period of the primary periodic task or the priority-5 periodic task. The priority-
5 periodic task is applicable only when you use an NX701 CPU Unit.
 Transmission Delay
The following methods are provided to calculate the transmission delay times for the CPU Unit and
the periodic tasks in which I/O is refreshed.
(1) Calculation with the Sysmac Studio
You can use the Sysmac Studio to display the transmission delay time for the EtherCAT
master. For details on this display method, refer to Displaying the Transmission Delay Time
for the EtherCAT Master with the Sysmac Studio on page 6-14.
(2) Calculation by a formula
You can use the following formula for the calculation by a formula. The vale that is found in
the formula is a roughly-estimated value.
The parameters necessary for the calculation are described below.
CPU Unit
Periodic task of the CPU Unit
in which I/O is refreshed
Calculation method
NX701 Primary periodic task • Calculation with Sysmac Studio
• Calculation by a formula
Priority-5 periodic task • Calculation with Sysmac Studio
• Calculation by a formula
NX102 and NX1P2 Primary periodic task Calculation by a formula
NJ-series
Transmission delay (μs) = 1.24 (μs) × Number of EtherCAT slaves + 0.082 (μs) × EtherCAT frame
length (bytes)
Parameter Description
Number of EtherCAT
Slaves
This is the number of all of the EtherCAT slaves in the same EtherCAT net-
work. An EtherCAT Slave Terminal is counted as one EtherCAT slave.
EtherCAT Frame
Length in Bytes
The EtherCAT frame length is the data byte size that is calculated under the
following conditions for the EtherCAT slaves in the same EtherCAT network
and for which I/O is refreshed in the primary periodic task.
• If the total data size is less than 64 bytes, use 64 bytes in the calculation.
• For EtherCAT slaves that have both input and output data, use the larger
of the input data size and output data size.
For example, the EtherCAT frame length in bytes for the following configu-
ration is as given below.
Configuration Example
• Two OMRON GX-series EtherCAT slaves: Data size of 20 bytes/slave
• One EtherCAT Slave Terminal: Input data size of 50 bytes and output
data size of 30 bytes
EtherCAT frame length = 20 bytes + 20 bytes + 50 bytes = 90 bytes