ProSoft Technology PTQ-101M - Manual (Page 145)

Reference PTQ-101M ♦ Quantum Platform
IEC 60870-5-101 Master Communication Module
ProSoft Technology, Inc. Page 145 of 181
May 14, 2008
As shown in the previous diagram, the module sends out 15 messages (15
points, 15 points and 10 points) instead of sending the whole 40 points in one
single message.
Note: This example shows the case where IOA Length = 3 bytes, COT Length = 2 bytes and
CASDU Length = 2 bytes.
Important: If the database parser gets a point index that is not valid, the whole database is set as
invalid and no points are reported. Because the index 0 is not valid (the protocol does not support
this index value), the driver considers it invalid. For example, if you set the size of the ASDU to 1
and you set a value of 1000 for a point index, this is also invalid as the indexes can only go from 1
to 255.
Balanced and Unbalanced Modes
The module supports balanced and unbalanced modes. In balanced mode, each
station may initiate message transfers. If the links from the master unit to several
slaves share a common physical channel, then these links must be operated in
an unbalanced mode to avoid the possibility of more than one device attempting
to transmit on the channel at the same time.
Select the communication mode with the following parameter:
Use Balanced Mode : 0 #0=No, 1=Use balanced mode
7.3.2 Module Initialization
After the module powers up, a specific initialization procedure occurs, depending
on the communication mode you selected (Balanced or Unbalanced).
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 ACK response.
Then the master sends two consecutive Class 1 requests. The slave responds to
the first Class 1 request with an "End of Initialization" response and the second
Class 1 request with an Ack message.