Rockwell Automation Publication 1766-UM001I-EN-P - June 2015 311
MicroLogix 1400 Distributed Network Protocol (DNP3) Appendix F
After the Backoff_Time, the MicroLogix 1400 tries again, either indefinitely, or
up to a configurable maximum number of retries. If a maximum is used, the
protocol considers this as a link failure.
Time Synchronization
The time value in the embedded RTC module of the MicroLogix 1400 controller
is updated by an RTC Function file every 2 seconds. This resolution is
insufficient to log DNP3 events in a DNP3 subsystem. Another timer,
incremented by 1 millisecond in the DNP3 Slave subsystem, serves to provide
appropriate resolution.
These two timers are synchronized by the following conditions:
• power up
• a request for time synchronization from DNP3 Master.
At power up, the DNP3 subsystem gets the time from an RTC function file in the
MicroLogix 1400. For the RTC function file to acquire the correct time, the
RTC module should be enabled before a power cycle to acquire the correct time
from the RTC function file.
In this example RTC function file, the RTC module is disabled. To enable it, click
"Set Date & Time" while it is online.
When there is a write request for time synchronization from a DNP3 Master,
DNP3 subsystem synchronizes its timer with the time from DNP3 Master and
the time in RTC module is synchronized with the time from DNP3 Master.
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