ProSoft Technology 5201-MNET-101S - Manual (Page 74)

Reference IEC-101 Slave ♦ ProLinx Communication Gateway
Protocol Manual IEC 60870-5-101 v3 Slave (Firmware version 3.xx)
Page 74 of 159 ProSoft Technology, Inc.
August 6, 2010
ASDU Configuration
The protocol specification document IEC 60870-5-3 describes the Basic
Application Data Units that are used in the protocol. It also defines the
Application Service Data Unit (ASDU) used by the protocol for data
communication.
You can configure the number of bytes to be used for the following ASDU
components:
Component Abbreviation Possible Number of Octets
Cause of Transmission COT 1 or 2
Common Address of ASDU CASDU 1 or 2
Information Object Address IOA 1, 2 or 3
These parameters must be configured to match the Master's configuration
(values shown are for example only; your application may require different
values):
The Common Address of ASDU is the station address. The gateway allows the
addressing of only the whole station (some devices allows different Common
Addresses to identify particular station sectors). You should configure the
Common ASDU Address with the following parameter:

Common Address of ASDU: 1
You should also configure the maximum number of bytes that the gateway will
support for each ASDU response to the Master unit. The range is from 25 to 252
bytes. You should verify the maximum number of bytes supported by the Master
because some IEC 60870-5-101 Master devices support messages with less
than 252 bytes.
Configure the following parameter to set the maximum number of bytes to be
transferred at every ASDU response.

Maximum ASDU Resp Len: 252
A value less than 252 can cause the gateway to break down the response to
send all points using more response messages, with each message containing
fewer bytes.