Omron NX-ECC201 User Manual page 258

12 Communications Performance
The maximum and minimum values of the I/O response time are calculated as follows: The minimum
value occurs when the time lag that is shown in the above figure does not occur.
Formula: Maximum I/O response time = Tcycle × 2 + Edelay + Etxj + Tmax-InTrans + Tmax-OutTrans
Formula: Minimum I/O response time =
The elements in the formulas are as follows:
• Tcycle: Task period of the primary periodic task in the CPU Unit
• Edelay: Transmission delay time of the EtherCAT master
• Etxj: Transmission jitter of the EtherCAT master
• Tmax-InTrans: Longest input data transmission time of all of the EtherCAT Coupler Units.
• Tmax-OutTrans: Longest output data transmission time of all of the EtherCAT Coupler Units.
• Tmax-InProc: Longest input data processing time of all of the NX Units.
• Tmax-OutProc: Longest output data processing time of all of the NX Units.
• Tnx-Indelay: Input delay time of the NX Unit
• Tnx-Outdelay: Output delay time of the NX Unit
Definitions of Formula Elements and Calculation Methods
This section defines the calculation formula elements and describes the calculation methods.
 Tcycle
This is the time that is set for the task period of the primary periodic task in the CPU Unit
 Edelay
This is the transmission delay time of the EtherCAT master.
Use the following formula to find Edelay.
Formula: Edelay = 1.24 × Number of EtherCAT slaves
*1. This is the number of EtherCAT slaves on the same EtherCAT network. An EtherCAT Slave Ter-
minal is counted as one EtherCAT slave.
*2. The EtherCAT frame length is data byte size that is calculated under the following conditions for
the EtherCAT slaves in the same EtherCAT network.
• 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 out-
put data size. For example, the EtherCAT frame length in bytes for the following configuration is as given
below.
EtherCAT frame length = 20 bytes + 20 bytes + 50 bytes = 90 bytes
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
 Etxj
This is the transmission jitter of the EtherCAT master.
The value is 100 μs.
12 - 4
+ Tmax-InProc + Tmax-OutProc + Tnx-Indelay + Tnx-Outdelay
Tcycle + Edelay + Etxj + Tmax-InTrans + Tmax-OutTrans
+ Tmax-InProc + Tmax-OutProc + Tnx-Indelay + Tnx-Outdelay
+ 0.09 × EtherCAT frame length in bytes
*1
*2
NX-series EtherCAT Coupler Unit User's Manual (W519)