Emerson DL8000 - Page 102

DL8000 Preset Instruction Manual
B-10 Modbus Communications Revised February-2016
Field
Description
value of the internal history index
and returns history data as one
less than the index requested.
Override Mode 2
Returns the history index as the
one less than the value of the
internal history index and returns
history data for the last valid index
if the request is equal to or
exceeds the number of requested
records.
Note: Contact technical support personnel to validate
how your host requests history index
information.
Group
Identifies a contiguous group of history points from a
single segment whose values the DL8000 can access
through a Modbus Function Code 03 request for a
user-defined Modbus register. You can define up to 20
groups.
Note: Figure A-3 shows a history table with the first
group configured for daily and period history
registers.
Period History
Register
Indicates the Modbus register number the DL8000
uses to acquire the group of periodic history points
defined in the Start History Point and End History Point
fields.
The typical value for this register is 704; you can define
other values if necessary.
Note: Use the Periodic Sample Rate field on the
History Segment Configuration screen
(Configure > History Segments on the
ROCLINK 800 menu bar) to define the sampling
frequency. For example, if you enter 60 in the
Periodic Sample Rate field, this is hourly history.
Daily History
Register
Indicates the Modbus register number the DL8000
uses to acquire the group of periodic history points
defined in the Start History Point and End History Point
fields.
The typical value for this register is 703; you can define
other values if necessary.
History Segment
Indicates the segment from which the DL8000 acquires
history. In this example, 0 is the General Segment.
Note: You must configure any segment you enter on
the History Segment Configuration screen
(Configure > History Segments on the
ROCLINK 800 menu bar).
Start History
Point
Identifies the first history point the DL8000 retrieves.
End History
Point
Identifies the last history point the DL8000 retrieves.
This value must be greater than or equal to the value
you enter in the Start History Point field.