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10 - 9
10 I/O Refreshing
NX-series EtherCAT Coupler Unit User’s Manual (W519)
10-3 I/O Re
freshin
g for Eth
er-
CA
T Slave T
ermin
als
10
1
0-3-4
I/O R
efreshing Method Oper
ation
An example of operation for each I/O refreshing method is provided in the following figure. This exam-
ple contains NX Units that operate with synchronous I/O refreshing in DC Mode and other NX Units that
operate with Free-Run refreshing.
Operation is as follows in Free-Run Mode:
• The NX bus refresh cycle is not synchronized with the primary period or process data communica-
tions cycle. The NX bus operates on its own cycle.
• The refresh cycle of the NX bus and the I/O refresh cycles of the NX Units are asynchronous.
Example of I/O Refreshing Method Operation
Primary periodic task Primary periodic task Primary periodic task
PLC Function
Module
EtherCAT transmission
time EtherCAT transmission
time EtherCAT transmission
time
Synchronized
NX Unit (No. 3)
Synchronized
NX Unit (No. 2)
Synchronized NX
Unit (No. 1)
EtherCAT
Coupler Unit
EtherCAT Master
Function Module
EtherCAT
communications path
Synced slave #1
EtherCAT Slave
Terminal #2
Synchronized NX
Unit (No. 3)
Synchronized NX
Unit (No. 2)
Synchronized NX
Unit (No. 1)
EtherCAT Coupler
Unit
EtherCAT Slave
Terminal #3
(Sync0) (Sync0) (Sync0)
ON/OFF response
time + Input filter time
ON/OFF response
time + Input filter time
Process data communica-
tions cycle (example: 500
μ
s)
Process data communica-
tions cycle (example: 500
μ
s)
Process data communica-
tions cycle (example: 500 μs)
Period of Sync0
(example: 500
μ
s)
Primary period
(example: 500
μ
s)
Primary period
(example: 500
μ
s)
Primary period
(example: 500
μ
s)
Refresh cycle of the NX
bus (example: 500
μ
s)
Refresh cycle of the NX
bus (example: 500
μ
s)
Refresh cycle of the NX
bus (example: 500
μ
s)
Free-run NX Unit
(No. 4)
Period of Sync0
(example: 500
μ
s)
Period of Sync0
(example: 500
μ
s)
Output data
transmission
time for
EtherCAT
Coupler Unit
Output data transmission time
for EtherCAT Coupler Unit
Output data
transmission
time for
EtherCAT
Coupler Unit
Input data
transmission
time for
EtherCAT
Coupler Unit
Input data transmission
time for EtherCAT
Coupler Unit
CPU Unit
EtherCAT slave
(D)
(C)
ch1 ch2 ch1 ch2 ch2 ch1 ch2 ch1 ch2 ch1 ch2 ch1
ch1 ch2 ch1 ch2 ch2 ch1 ch2 ch1 ch2 ch1 ch2 ch1
All Units with synchronous input refreshing
read their inputs simultaneously (A).
AD conversion time
for each Unit
ON/OFF response time
DA conversion
time for each Unit
All Units with synchronous output refreshing
refresh their outputs simultaneously (B)
ON/OFF response time
DA conversion time for
each Unit
AD conversion time
for each Unit
Processing of free-run NX Unit (No. 4)
Processing of free-run NX Unit (No. 4)