Omron NX701-17 Series User Manual page 124

6 Process Data Communications and SDO Communications
 Timing of I/O Refreshing
The table below shows when I/O is refreshed for each type of EtherCAT slaves.
Task that controls I/O
Primary periodic task
Priority-5 periodic task
Priority-16 periodic task
*1 Refer to the manual for the specific slave to check if the I/O refreshing period agrees with the communica-
tions cycle supported with the slave. An error occurs if you use the Sysmac Studio to set the I/O refreshing
timing to a communications cycle that is not supported with the slave. The error occurs only with the
OMRON slaves that is set for synchronization.
*2 You can use the priority-5 periodic task only with the NX701 CPU Units.
*3 EtherCAT communications take place in the I/O refreshing timing for the primary periodic task. If the
priority-16 periodic task is used to control EtherCAT slaves, data will be refreshed by I/O refreshing in the
task period of the priority-16 periodic task.
Relationship between tasks to execute I/O refreshing, process data communications cycle, and
motion control is shown as follows.
• NX701 CPU Units
Task to execute
I/O refreshing
Primary periodic task
Priority-5 periodic task
• NJ-series CPU Units and NX1P2 CPU Units
Task to execute
I/O refreshing
Primary periodic task
 Restrictions for Multiple Communications Cycles
With the NX701 CPU Unit, you can perform process data communications at each task period spe-
cific to the primary periodic task and the priority-5 periodic task. On the other hand, there is only one
EtherCAT network line. Therefore, some restrictions are placed on the process data communica-
tions in multiple communications cycles, as shown below.
• When the number of slaves controlled by the master increases, the process data communications
cycles of both primary periodic task and priority-5 periodic task will get longer.
Consider the following countermeasures if the process data communications cycle for each task
exceeds the task period.
• If you want to maintain the number of the slaves, increase the task period of the task whose
process data communications cycle exceeds the task period.
• If you want to maintain the task period, decrease the number of the slaves.
• The process data communications for the primary periodic task is processed in priority over the
process data communications for the priority-5 periodic task. Therefore, the size of process data
for the priority-5 periodic task that can be processed becomes smaller than that for the primary
periodic task even if both tasks have the same task period.
Consider the following countermeasures if the process data communications cycle for the priority-
5 periodic task exceeds the task period.
• If you want to maintain the process data size of priority-5 periodic task, increase the period of
the priority-5 periodic task.
• If you want to maintain the period of priority-5 periodic task, decrease the process data size of
the priority-5 periodic tasks that are assigned for the entire slaves.
6-6
Task period of the primary periodic task
*2
Task period of the priority-5 periodic task
Task period of the primary periodic task
communications cycle
Process data communications cycle 1
Process data communications cycle 2
communications cycle
Process data communications cycle
NJ/NX-series CPU Unit Built-in EtherCAT Port User's Manual (W505)
Execution period of I/O refreshing
Process data
Process data
*1
*1
*1*3
Motion control
Motion control 1
Motion control 2
Motion control
Motion control