ProSoft Technology 5201-MNET-101S - Manual (Page 78)

Reference IEC-101 Slave ♦ ProLinx Communication Gateway
Protocol Manual IEC 60870-5-101 v3 Slave (Firmware version 3.xx)
Page 78 of 159 ProSoft Technology, Inc.
August 6, 2010
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 gateway’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: