EVAL-AD421EB

REV. A

–4–

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.