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Reference Manual
00809-0100-4832, Rev AA
October 2004
Rosemount 3095FC
3-44
Modbus - History Collection
The Modbus protocol sends the Hourly (periodic) and Daily History. Refer to
“History Access Registers Tab” on page 3-44. Each record contains a time
and date stamp and all of the history archives for which the Register Number
is configured. The Modbus Function Code 03 and the History Archive
Register are used to collect the archived data. Two Modbus registers indicate
the current Hourly and Daily history index as selected in the Archive Type
field. These can be configured in the Hourly History Index Register and the
Daily History Index Register. These indexes identify the current history
archive at which data was last logged.
To collect the Hourly and Daily history a standard Modbus Function Code 03
is used. The Register Number field is used to address the individual History
Archive Register. The Daily Index, Hourly Index, and Event/Alarm data fields
are used to address a history index number. The response message 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 points for that History Archive Register.
The date stamp for history uses the current year and does not figure the
number of years since 1980.
NOTE
When in Modbus with EFM extensions mode, the time stamp is in the HHMM
format. In addition, the date time stamp is returned before the time stamp.
History Access Registers Tab
See Figure 3-27 on page 3-45
The History Archive Register is a single register that can contain one or more
history points for retrieval of the Event Log, Alarm Log, and Historical
Archives. Historical data is contained in Point Type 55 up to 35 days of hourly
data for each of its history points can be stored. The points mapped on the
history tab are configured on the Configure > History Points screen.
1. Enter Configure > Modbus > Configuration > History Access
Registers tab.
2. Enter the modbus Register Number used to acquire the Daily Index
values.
3. Enter the Modbus Register Number used to acquire the Hourly Index
values.
4. Enter the Modbus Register Number used to acquire the Events/Alarm
logs.
5. Enter the Modbus Register Number used to acquire the group of
history points defined in the Starting History Point and Ending History
Point fields without having to define each history point separately.
6. Enter the Starting History Point to acquire a group of history points
without having to define each history point separately, enter values in
the Starting History Point and Ending History Point fields. The Starting
History Point value is the first history point to be retrieved.
7. Enter the Ending History Point to acquire a group of history points
without having to define each history point separately, enter values in
the Starting History Point and Ending History Point fields. Then
Ending History Point is the last history point to be retrieved.