EVAL-AD421EB Datasheet, PDF (4/7 Pages) Analog Devices – Evaluation Board for Loop Powered 4-20mA DAC

EVAL-AD421EB
The evaluation software does not allow another application
running under Windows to access the printer port while it is
running. Control of the printer port is returned when the
AD421 application program is quit.
MAIN MENU WINDOW
Once the OK button of the port selection window has been
pressed the user is presented with the Main Menu Window for
the application. The window is called AD421 Evaluation Board
Utility and is as shown in Figure 3. This utility contains the
following sections: interface, setup output and programmed
output.
INTERFACE SECTION
The interface section contains buttons that control the method
in which data is loaded to the AD421 and also the printer port
selection. The following is a description of these buttons.
Load Input Reg
When this button is clicked the input register of the AD421 is
loaded with the data as programmed in the Setup Output
section. Data is only loaded to the input register and is not
transferred to the DAC register. No output update takes place
in this case.
DAC Latch
When this button is clicked the data in the input register of the
AD421 is transferred to the DAC register and an output update
takes place. This basically activates the LATCH input to the
AD421.
Load + Latch
When this button is clicked the input register of the AD421 is
loaded with the data as programmed in the Setup Output
Section and the LATCH signal is also activated updating the
output of the AD421. This is a combination of the previous two
buttons.
Port Selection
This button returns the user to the previous menu on Parallel
Port Selection. The selected port appears in the box at the
bottom on the interface section.
SETUP OUTPUT SECTION
This section allows the user to select one of three current output
setup modes and also allows the selection of either 4-20mA
normal mode of operation or the selection of an alarm current
mode where the current range is from 3.5-24mA. The following
is a description of these buttons.
Setup Mode
There are three selections in this setup, the programmed output
current can be programmed as a straight mA by selecting the
mA button.
The second button, % Fullscale, allows the output current to be
programmed as a percentage of the fullscale output.
The third selection allows the user to enter the HEX data value
to be loaded to the input register as the method of programming
the output current.
Alarm Current On
This button is used to select between the normal 4-20mA
output and the alarm current output. When this button is not
selected the normal 4-20mA output range is selected. When the
alarm current on is selected an "x" appears in the box and the
output range can be programmed from 3.5mA to 24mA.
PROGRAMMED OUTPUT
This section shows the programmed output current as a current
in mA, as a % of Fullscale and as the HEX value that has been
written to the input register. The Binary Output Box shows in
the form of a LED display the data that has been loaded to the
AD421.
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REV. A