Omron NJ101-10 Series, User Manual

Page: 168 / 280


When the Task Period of the Primary Periodic Task is Smaller than 4 ms
Minimum message response time (ms) =
Task period of the task that executes the SDO communications instruction
+ (Slave SDO processing time
*1
/Task period of primary periodic task)
*2
× Task period of primary periodic
task
+ (SDO response data size/Transmission size)
*2
× Task period of primary periodic task
*1. The slave SDO processing time depends on the slaves. Refer to relevant manuals for each slave.
*2. Round up the calculation result in parentheses to make an integer.
The transmission size is determined by the task period of primary periodic task as shown below.
Task period of the primary periodic task Transmission size
125 μs 64 bytes
250 μs 128 bytes
500 μs or longer 256 bytes
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 as-
signed to the primary periodic task.
Performance Model Example
Task period of primary periodic task [ms] 1
SDO response data size [byte] 512
Slave SDO processing time [ms] 1.2
Message response time [ms] 5
IO UPG MC
Task period
(1 ms) Task period
(1 ms) Task period
(1 ms) Task period
(1 ms) Task period
(1 ms) Task period
(1 ms)
Execution of SDO
communications
instruction
completed.
Slave SDO processing time
IO UPG MC IO UPG MC IO UPG MC IO UPG MC IO UPG MC
Frame
sent.
SDO
request
received. SDO response
generation
completed. EtherCAT master captures
SDO response data from slave:
256 bytes per frame.
IO: I/O refreshing
UPG: User program execution
MC: Motion control
EtherCAT master processing
Slave SDO processing
Line delay
SDO
communications
instruction
executed.

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 the SDO communications instruction
+ (Slave SDO processing time
*1
/Divided period
*2
)
*3
× Divided period
+ (SDO response data size/256 bytes)
*3
× Divided period
*1. The slave SDO processing time depends on the slaves. Refer to relevant manuals for each slave.
*2. The divided period is obtained by dividing the task period of primary periodic task. If the task period of
primary periodic task is equal to or more than 4 ms, the EtherCAT master sends a message communica-
tions 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.
6 Process Data Communications and SDO Communications
6-22
NJ/NX-series CPU Unit Built-in EtherCAT Port User's Manual (W505)