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Example 2: Local Input - Remote Output
Maximum reaction time (ms)
= Switch reaction time
+ NE1A-SCPU01-A local input/remote output reaction time
+ Network reaction time
+ NE1A-SCPU01-B remote input/local output reaction time
+ Actuator reaction time
= Switch reaction time
+ ON/OFF delay (NE1A-SCPU01) + 3.5 + 7 2
+ 28
+ 6 + 2.5
+ Actuator reaction time
= 54.0 + ON/OFF delay + Switch reaction time + Actuator reaction time
3-3-3
Verifying the Maximum Reaction Time
Check that the calculated maximum reaction time meets the required specifications in all safety chains. If the
reaction time exceeds the required specifications, re-examine the network design, taking into consideration
the following points for the maximum reaction time to meet the requirement specifications:
•
Shortening the EPI will shorten the network reaction time. Shortening the EPI, however, narrows the
network bandwidth that can be used for other connections.
•
The NE1A-SCPU01 cycle time is automatically calculated based on the program size, the number of
connections, etc. It is also possible to use different NE1A-SCPU01 Controllers for safety chains that
require a high-speed reaction time and other safety chains.
3-3 Calculating and Verifying the Maximum Reaction Time
SNC cycle time = 7 ms
I/O refresh cycle = 3.5 ms
NE1A-SCPU01
Switch
A
SNC cycle time = 6 ms
I/O refresh cycle = 6 ms
NE1A-SCPU01
B
Safety connection (EPI = 7 ms)
network reaction time = 28 ms
Actuator
DeviceNet
67
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