of the recorded data are sequential. During the fault record buffer overflow the client
can notice a jump in the sequence numbers when some fault records are lost. The gap
between the new and the previous sequence number reveals exactly how many records
have been lost.
Unread records Left
This register shows how many unread fault records still remain unread for the client
in question at a particular moment.
Time stamp registers
The time stamp registers usually hold two data values in the high and low byte of the
registers. High byte value = RegisterValue DIV 256, Low byte value = RegisterValue
MOD 256. An exception is the milliseconds register which contains the milliseconds
0...999 coded as such. Time stamp also contains a time quality register.
Time quality
Table 36:
Information contained by the 16 bit (bits 15..0) register
Bit
Meaning
Values
15
Event time stamp format
0 = Local time
1 = UTC time
14
Time stamp source
0 = Internal
application
1 = Modbus stack
13
Clock not synchronized
0 = Synchronized
1 = Time not
synchronized
12
Clock failure
0 = Clock OK
1 = Clock failure
11...0
Reserved
0
Event time stamp format bit 15
The time stamp format can be selected with a Modbus parameter via the LHMI or the
parameter setting tool.
Event time stamp source bit 14
The time stamp can be generated by the IED application, that is accurate time, or by
Modbus. If generated by Modbus, the change values are detected by the Modbus
background scan task. Since there is a latency time between the value change and the
time when Modbus detects the change, in this case the time stamp is not accurate.
Clock not synchronized bit 13
The quality information bit is set in the IED's real-time clock if the IED has not been
synchronized.
Clock failure bit 12
The quality information bit is set in the IED's real-time clock if the clock has a severe
failure. Do not rely on this time stamp.
1MRS757645 B
Section 3
Vendor-specific implementation
620 series
59
Communication Protocol Manual
