as no new selection write operation is performed, the contents of the
11 event record registers are not changed.
3.4.9.3
Other event record registers
Sequence number
Every Modbus event record is given a sequence number. The sequence number runs
from 1 to 65535 and then rolls over to 1 again. The client can check that the sequence
numbers of the recorded data are sequential. During the event buffer overflow the
client can notice a jump in the sequence numbers when some event records are lost.
The gap between the new and the previous sequence number reveals exactly how
many event records have been lost.
Unread records left
This register shows how many unread event records still remain unread for the client
in question at a particular moment.
Time stamp registers
Time stamp is either in local time or UTC time. The time stamp alternative is selected
with a Modbus parameter.
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. The Milliseconds register is an exception as it contains the milliseconds
0...999 coded as such.
Event type
This register contains information to interpret the event data correctly.
Table 27:
Information contained by the 16 bit 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
synchronize
d
0 = Synchronized
1 = Time not synchronized
12
Clock failure
0 = Clock OK
1 = Clock failure
11
Reserved
0
10
Reserved
0
Table continues on next page
1MRS757645 B
Section 3
Vendor-specific implementation
620 series
51
Communication Protocol Manual
