112 Rockwell Automation Publication 2080-UM002N-EN-E - November 2022
Chapter 6 Micro870 Controller Distributed Network Protocol
• Hold Time after Class3 Events (x1s)
• DNP3 Object Data
• DNP3 Object Config
• Content of the Config File
In some cases, the controller may not send an Unsolicited Response even though the
parameters are configured properly.
• Normally, when the parameter Enable Unsolicited On Start Up is checked, the controller
initiates an Unsolicited Response with the function code ENABLE_UNSOLICITED(20), if
there are any events logged into the event buffer. However, when a request with the
function code DISABLE_UNSOLICITED(21) is received, an Unsolicited Response will not be
sent.
• When the parameter Enable Unsolicited On Start Up is unchecked, the controller does
not trigger the Unsolicited Response until a request with the function code
ENABLE_UNSOLICITED(20) from the DNP3 Master is received.
Figure 7
shows how to initiate and send the Unsolicited Response. Master Node 0 in the DNP3
Slave configuration page indicates that the Unsolicited Response is reported to the Master
with the node address 3.
Figure 7 - Initiate and Send Unsolicited Response
The parameter for Unsolicited Response in the DNP3 Slave configuration indicates that the
Unsolicited Response is reported for all the communication ports (Serial and Ethernet) that are
defined. In this example, Initial Unsolicited Response is sent on startup and all events of class
1, 2 and 3 are reported. Since Hold Times are configured to 5 seconds, generated events are
reported after 5 seconds.
Collision Avoidance The controller currently supports the first of the two methods listed below for collision
avoidance.
• Detecting transmitted data (TX/RX line on RS-485 communication).
• Detecting out-of-band carrier (DCD on RS-232C communication).
When the controller is connected to RS-485 network, it monitors all data on the link. If the
controller is preparing to transmit a packet and finds the link busy, it waits for an interval
defined by the Backoff_Time until it is no longer busy.
Backoff_Time = Pre Transmit Delay (x1 ms) + Max Random Delay (x1 ms)
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