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Reference Manual
00809-0100-4832, Rev AA
October 2004
Rosemount 3095FC
3-46
Table 3-5. History, Event, and
Alarm Functionality
The 3095FC supports the Modbus with EFM extensions method for retrieving
alarms, events, and history. When a Function code 3 request referencing
defined Events/Alarms Register (usually 32) is received, it begins to collect
records from first the Event Log and then the Alarm Log, starting where the
last poll left off. The 3095FC will collect records until either there are not any
more new events/alarms or the maximum of twelve records have been
collected. The 3095FC sends the information back to the host, which in return
replies with Function Code 5, referencing the same Events/Alarms Register,
indicating that the points have been received and that the host is ready for the
next twelve records.
When the 3095FC receives a Function Code 3 request referencing one of the
user-defined Periodic History Registers or Daily History Registers, the
number of registers field is interrupted as an index into the specific history log.
The reply message contains the date and time stamp and historical values
configured for the specified for that index.
Reading Events / Alarms Register
The Modbus request to read the Event/Alarm log (see Table 3-6) uses the
standard read Function Code 03 and the Event/Alarm Register (parameter
#0) in the Modbus Special Function Table (point type 39). In this request,
the number of registers is included to maintain format compatibility but is
ignored by the receiving 3095FC unit. For the date stamp in the events
and alarms returned, the year (YY) is really the number of years since
1980 (for example, the current year is 1997, so the year (YY) for the date
stamp would be 17).
Acknowledging Events / Alarms
The Modbus request to acknowledge the event/alarm log uses Function
Code 05 and the Event/Alarm Register (parameter #0) in the Modbus
Special Function Table (point type 39). In this request, the number of
registers is always one (1).
Function
Code
Register Field Data Field Description
3 7160 – Daily Index Ignored Response contains current daily index
3 7161 – Hourly Index Ignored Response contains current hourly index
3 32 – Event/Alarm Register Ignored Response contains Events and Alarm records. Maximum number of bytes
returned is 240 (12 records of 20 bytes each). Events are returned before
Alarms are returned. The format is displayed in Table 3-6.
5 32 – Event/Alarm Register Ignored After Events and Alarms have been returned, there must e an
acknowledgement made so that the same Events and Alarms are not returned
on the next request.
3 703 – 7160 – Daily History History Archive
Register (0 to 34)
Response contains two floating point values for the time and date stamp of the
history archive (time stamp = HHMMSS and date stamp = MMDDYY) and
floating point values for each of the defined history point for that History Archive
Register.
3 704 – Hourly Index History Archive
Register (0 to
8.39)
Response contains two floating point values for the time and date stamp of the
history archive (time stamp = HHMMSS and date stamp = MMDDYY) and
floating point values for each of the defined history point for that History Archive
Register.