ProSoft Technology MVI56-101S - Manual (Page 119)

MVI56-101S ♦ ControlLogix Platform Reference
IEC 60870-5-101 Slave Communication Module User Manual
ProSoft Technology, Inc. Page 119 of 193
August 2, 2011
Unbalanced mode
In order to start communications between the Master and the slave units, the
Master tries to establish the link connection by transmitting repeated "Request
Status of Link" at specific time out intervals. When the module’s link is available,
it will respond with a "Status of Link" response. Then, the Master transmits a
"Reset of Remote Link" message and the slave responds with an Acknowledge
(ACK) response. Then the Master sends two consecutive Class 1 requests. The
slave responds the first Class 1 request with an "End of Initialization" response
and the second Class 1 request with an ACK message.
The following illustration shows a typical initialization procedure for the
unbalanced mode:
Master
101
Slave
Status of Link Request
Status of Link Response
Reset Remote Link
ACK
Class 1
End Of Initialization
Class 1
ACK / Data Not Available