ProSoft Technology MVI69-101S - Manual (Page 93)

Reference MVI69-101S ♦ CompactLogix or MicroLogix Platform
IEC 60870-5-101 Slave Communication Module
ProSoft Technology, Inc. Page 93 of 149
March 16, 2009
These parameters must be configured to match the master's configuration, as
shown in the following example:
Common Address of ASDU len: 2 #Range is 1 or 2 octets
Inform. Object Address len: 3 #Range is 1, 2, or 3 octets
Cause of Trans Octets : 2 #Number of COT octets (1 or 2)
The Common Address of ASDU is the station address. The module only allows
the addressing of 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 # Range depends on number of octets for
# CASDU
You should also configure the maximum number of bytes that the module will
support for each ASDU response to the master unit. The range lies between 25
and 252 bytes. You should verify the maximum number of bytes supported by the
master because some IEC 60870-5-101 master devices only 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 #Max ASDU response message
A value less than 252 can cause the module to break down the response to send
all points using more response messages, with each message containing fewer
bytes.
Example - Changing the ASDU Length:
Considering that the master sends a General Interrogation request to poll forty
M_ME_NB points (measured scaled points in Unbalanced Mode):
If Maximum ASDU Resp Len = 252: