Omron CJ1W- ECT21 Operation Manual page 91

I/O Response Time Formula
A formula is provided below to calculate the I/O response time.
Maximum I/O Response Time = Tmaster + (4 x Tslave) + (2 x Tcj_plc) + (2 x Ttrans)
The elements used in the maximum I/O response time formula are described below. Units of these ele-
ments are in ms.
 Tmaster
The cycle time of the EtherCAT master is assumed to be the same as the process data communica-
tion cycle. Use the process data communication cycle that is set in the EtherCAT master.
 Tslave
The EtherCAT Slave Unit processing time can be calculated with the formula below.
Tslave = 1.5 + (0.0007 x (IN data area size + OUT data area size))
Units of IN and OUT data area size are in channels (CH).
 Tcj_plc
The PLC cycle time can be obtained by referring to the CPU Unit's operation manual.
The I/O refresh time of the PLC is the maximum time required for I/O data to be exchanged between
the CPU Unit and the EtherCAT Slave Unit. The PLC cycle time is increased when an EtherCAT
Slave Unit is mounted as shown in the formula below.
I/O Refresh Time = A + (B x (IN data area size + OUT data area size))
Units of IN and OUT data area size are in channels (CH).
Use the values of A and B in table below for the CPU type that has the EtherCAT Slave Unit
mounted.
CPU type
CJ1M
CJ2H
CJ2M
 Ttrans
The transmission time of the EtherCAT master can be calculated with the formula below.
Ttrans = ((1.24 x Number of EtherCAT slaves) + (0.09 x EtherCAT frame length in bytes)) / 1000
The number of EtherCAT slaves represents the number of EtherCAT slaves that are present on the
same EtherCAT network. An EtherCAT Slave Unit is considered to be one EtherCAT slave.
The EtherCAT frame length in bytes represents the data byte size of the EtherCAT frame on the
same EtherCAT network.
CJ-series EtherCAT Slave Units Operation Manual (W541)
Value of A
0.3
0.3
0.3
4 EtherCAT Communications
Value of B
0.0008
0.0024
0.0024
4
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