Applied Systems Engineering ASE2000 User Manual page 197

Interoperability Options
There are three addressing components, the Data Link (DL) address, Common address of
ASDU, and Information Object address. The protocol allows the size of these fields to vary from
system to system, although they must be the same for all devices in a given system.
Also, each address can be structured or not. A structured address implies that the total address
size, for example 2 octets (16 bits), is logically structured into two subfields of, for example, 8
bits each. This is purely an interpretation convention. For example, assume the value of a 2-octet
Common Address is 513. This is hex 0x201. If interpreted as an unstructured number, the value
is 513. If interpreted as a structured number composed of two 8-bit subfields, the value could be
displayed as 2.1 (the high 8-bit value is 2 and the low 8-bit value is 1).
The IEC 60870-5-101 menu allows specification of both the address sizes, whether they should be
interpreted as structured or unstructured values, and how structured values should be displayed.
1-octet addresses can only be unstructured
2-octet addresses can be unstructured, or structured with an address format of 8.8. This displays
the 2-octet, 16-bit field, as two 8-bit values
3-octet addresses can be can be unstructured, or structured with an address format of:
• 8.8.8 - three 8-bit values,
• 16.8 - a 16-bit value followed by an 8-bit value, or
• 8.16 – an 8-bit value followed by a 16-bit value
DL Address is the data link address size, 0, 1, or 2 octets. 0 octets is allowed only for balanced
mode
Common Address is the common address of ASDU size, 1 or 2 octets
Information Object is the information object address size, 1, 2, or 3 octets
Cause of Transmission is the size of the cause of transmission field, 1 or 2 octets. For 2 octets,
the first is the cause and the second contains an origination address
Balanced Mode Options
Enabled is set to enable balanced mode, clear for unbalanced mode
Controlling Station Direction (A -> B) For balanced mode, indicates that the DIR bit is set in
messages originating from the Controlling station. If not selected, the DIR bit is set in messages
originating from the controlled station. Not used inn unbalanced mode
Unbalanced Mode Options
Class Scan Period is only used when operating as a master (controlling station) in unbalanced
mode. In addition to exchanges that are explicitly enabled for transmission, this option instructs
the ASE2000 how often to issue a Class 1 or Class 2 request
Short Ack is set to transmit the 1-octet Short Ack code when applicable. If not set, then the multi-
octet Data Link acknowledgement message is sent
Short Ack Class Response is set when RTU is to send a Short Ack code when no data is
available instead of a negative response code
ASE2000 V2 Communication Test Set User Manual 197