Omron NX701-17 Series User Manual page 142

6 Process Data Communications and SDO Communications
The following timing chart shows an example of the timing from an execution of the SDO communi-
cations instruction to the completion of the instruction execution, based on the performance model
below.
Here, it is assumed that the program that executes the SDO communications instructions is
assigned to the primary periodic task.
Performance Model Example
Task period of primary periodic task [ms]
SDO response data size [byte]
Slave SDO processing time [ms]
Message response time [ms]
IO: I/O refreshing
UPG: User program execution
MC: Motion control
SDO
EtherCAT master processing
communications
instruction
Line delay
executed.
Slave SDO processing
 When the Task Period of the Primary Periodic Task is 4 ms or Longer
Minimum message response time (ms) = Task period of the task that executes SDO communications
*1 The slave SDO processing time depends on the slaves. Refer to the manual for the slave.
*2 The divided period is obtained by dividing the task period of primary periodic task. If the task period of pri-
mary periodic task is equal to or more than 4 ms, the EtherCAT master sends a message communications
frame to a slave and receives a message response data from the slave, according to the divided period.
Assign 1 ms to the divided period for this calculation.
*3 Round up the calculation result in parentheses to make an integer.
6-24
Task period Task period
(1 ms) (1 ms)
IO UPG MC IO UPG MC
Frame
sent.
Slave SDO processing time
SDO
request
received.
instruction
period
1
512
1.2
5
Task period Task period
(1 ms) (1 ms)
IO UPG MC IO UPG MC
SDO response
generation
completed.
+ (Slave SDO processing time
+ (SDO response data size/256 bytes)
NJ/NX-series CPU Unit Built-in EtherCAT Port User's Manual (W505)
Task period Task period
(1 ms) (1 ms)
IO UPG MC IO UPG MC
Execution of SDO
communications
instruction
completed.
EtherCAT master captures
SDO response data from slave:
256 bytes per frame.
*1 *2 *3
× Divided
/Divided period )
*3
× Divided period