ProSoft Technology MVI71-DNP - Manual (Page 140)

MVI71-DNP ♦ PLC Platform Reference
DNP 3.0 Master/Slave Communication Module
Page 140 of 172 ProSoft Technology, Inc.
August 23, 2007
Error Code Name Description
1008 Read operation not supported
for object/variation The application layer response message
contains an object that does not support the
read function.
1009 Operate function not supported
for the object/variation The application layer response message
contains an object that does not support the
operate function.
1010 Write operation not supported
for the object/variation The application layer response message
contains an object that does not support the
write function.
5.12 Event Size Computation
The minimum event buffer size required to avoid overflow can be computed as
follows:
((number of static points)*(rate per second scan of change function)) /(rate per
second of master event data poll)
For example: 51 binary input points are scanned 2 times each second and polled
by the master station about every 5 seconds. The minimum number of binary
input events is:
(51 * 2)/.02 = 510 events
This computation assumes the unlikely event that all data points will change in
consecutive calls to the scan of change function. If an event buffer overflow
condition occurs, the internal indication bit, BUFFER OVERFLOW, will be set. If
the system you are working with is fairly stable, the following equation can be
used to compute the event buffer size:
(number of points that change per change function * rate per second of scan of
change function)*(number of seconds between master event data poll)
For example: 1000 binary input points are scanned 2 times each second and
polled by the master station about every 5 seconds. Only about 5 points change
state every scan of the change function call.
(5 * 2) * 5 = 50 events required
The number of events that can be defined in the system is limited to 400. The
event buffer will overflow in systems which are very dynamic unless one of the
following conditions exist:
The master frequently polls the slave device for events to keep the buffer empty.
OR
The slave is configured to send unsolicited messages to the master station. This
method requires full-duplex operation of the network because the slave may be
sending a message during a request from the master station.
In order to disable the report by exception feature in the module, set the number
of events to 0 for both the binary and analog input events in the configuration (N[
]:5 and 6 in the system configuration block). This will cause the slave to never
return any data on object 2 and 32 and class 2 and 3 master station requests.