Section 3
1MAC052634-MB D
Vendor-specific implementation
30
615/620 series ANSI
Communication Protocol Manual
Table 20:
Event record structure
The event record can have two different data object identification alternatives. The data
object can be identified by the Modbus address on which the object resides or it can be
identified by a unique id which is platform dependent.
The identification alternative is selected with the Modbus parameter
Event ID
.
3.3.8.2
Single event record reading
As long as there are unread Modbus events available for the Modbus client in question, bit
0 of Modbus SSR3 register remains “1”.
Events are read in two steps. First, the client writes a selection code to the Event selection
register. The selection code defines the type of read operation that the client wants to
perform. The selected event record is loaded by the IED into the following 11 registers.
Second, the client reads out the 11 registers in one multiple register read operation.
Selection code 1: Reading the oldest unread record
When writing the selection code 1, the IED first checks the client. If the client has read
events before, the IED knows which internal event has been sent to this specific client
during the last reading. The IED then loads the next event, that is the oldest unread event,
Address
Register
Values
Comment
4xxxx + 1
Event selection
1...4 and -1...-499
Write register
4xxxx + 2
Sequence Number
0...65535
4xxxx + 3
Unread records left
0...499
4xxxx + 4
TimeStamp
(Year,Month)
High byte:year, low byte:month
4xxxx + 5
TimeStamp (Day,
Hour)
High byte:day, low byte:hour
4xxxx + 6
TimeStamp (Min, Sec)
High byte:min, low byte:second
4xxxx + 7
TimeStamp
(Milliseconds)
Word: milliseconds (0...999)
4xxxx + 8
Event type
See separate description
4xxxx + 9
Data Object ID 1
0 or UID high word
See separate description
4xxxx + 10
Data Object ID 2
Modbus address or UID low
word
4xxxx + 11
Data Value
Modbus data value
Value into which object has
changed
4xxxx + 12
Data Value
Additional data
Event records can be read by using two commands, function 5 for the write
operation and function 6 for the read operation, or by using function 23 that
includes write and read operations in the same transaction.
If event records are read by using two commands, the positive confirmation
to the write select operation tells the client that an event record has been
loaded for reading. Another way to detect the positive confirmation is by
monitoring the state of SSR3 bit 8.
