User`s guide

Operating the DX LCD Display 4-11
Trend Data
If the connected DX controller supports Trend, it can collect and store
Trend data for up to 12 analog and logic variables. An analog variable
corresponds to an analog item in the DX controller, such as an analog
input. A logic variable in the DX controller is a byte value
representing eight digital bits, such as the eight digital inputs DI1 to
DI8. Trend data is collected for all eight bits of the logic variable.
The analog trend collects the current values of the variable at a
user-defined sampling rate and displays this data graphically as a line
graph plot. The logical (digital) trend collects Change-of-State (COS)
events on all eight bits of the variable, and displays this data in a list
format, using separate lists for each bit of the logic variable.
The 12 variables (either analog or logic) for which Trend data is to be
collected are defined in the DX controller configuration, along with
other parameters for each variable, such as sampling rate and sampling
mode.
The 12 trend variables may also be defined for display on the DX LCD
Display. In the display configuration, you assign names to the trend
variables and define units for the analog trend variables. You also
assign names to each bit of the logic trend variables and define names
for the states of each bit.
Since the display configuration may not match the configuration of the
DX controller to which it is connected (for example, the DX controller
configuration has been updated, but the display configuration has not),
there may be a mismatch in the trend variables. In that case, the Trend
Data screen shows Trend Definition Mismatch instead of the trend
variable name for those variables where the mismatch occurred.
For more information on the Trend Data feature, see the documents
listed in the Introduction to DX LCD Display chapter in this guide.