EVAL-AD7476 Datasheet, PDF (7/12 Pages) Analog Devices – Evaluation Board for 1MSPS, 12-/ 10-Bit ADCs

EVAL-AD7476/77CB
There are two configuration files for the AD7476. (these are
AD7476 and AD7476D) and two for the AD7477 (these are
AD7477 and AD7477D). Each file is particular to a certain
mode of operation for the device. See modes of operation
selection in the AD7476/77 datasheet. The AD7476 file is
the normal mode program for the AD7476. This should
execute when the F3 button is pressed after the AD7476
configuration file has been loaded. When the button is
pressed the conversion result will be output on to the screen
as either an fft plot or as a historgram.
The AD7476 program also offers the user the option of
entering the "power down" mode. This can done by entering
the setup screen (see figure 4) and using the Power down
button. As there will be no valid data from this operation,
there will be no result on screen. To exit the "powerdown"
mode the user must "Power up" the part before preforming
a valid conversion. This can be done by again entering the
setup screen and pressing the "Power up" button. As there is
no valid data from this dummy conversion there is no result
to be output on screen.
The AD7477 program offers the same options as the AD7476
program but it is configured for a 10 bit part (AD7477).
When the AD7476D configuration file is loaded it offers the
user a "power up - convert - powerdown" sequence option.
This program is ideal for use when the device is not being
operated constantly, as it saves on power. The 12 bit result
from the conversion is output on the screen as either an fft
plot or a histogram.
To perform the same sequence (power up - convert -
powerdown)on the 10 bit AD7477 part, the AD7477D
configuration file should be used.
MAIN SCREEN
Figure 4. Setup Menu Screen
The top left part of the main screen contains eight buttons
which are selected using the mouse or by using the function
keys from the keyboard. These buttons and the actions they
perform are:
F1: Info. This button shows information on the software.
F2: Setup. This button activates the setup menu.
F3: Samp. When this key is pressed, the software causes
the AD7476/77 to perform a number of conversions
as determined by the setup menu (see above). The
data from these conversions is then analyzed by the
AD7476/77 evaluation software. Another set of
samples may be taken by pressing the F3 key again.
F4: Cont. Pressing this button causes the software to
repeatedly perform conversions and analyze them.
Once the conversions and analysis has been done for
one set of samples, the software automatically repeats
the process. It continues to do this until the ESC key
is pressed.
F5: Save. This saves a set of samples to a file for use either
at a later date or with other software. The samples can
be saved either as "volts", "ints" or "binary". The
format of all these files is ASCII text. Note that the
AD7476/77 software can only load files saved in the
"ints" format. Files saved in the "volts" and "ints"
formats can be used with packages such as Mathcad.
Files saved in the "binary" format are for viewing
purposes only.
F6: Load. This allows the user to load data from a file
with a .DAT extension. Only data that was saved as
ints can be loaded and analyzed. A configuration file
must be loaded via the "F2 Setup" menu before the
data file can be analyzed. If there is no EVAL-
CONTROL BOARD connected to the PC, then the
"no prog" button in the "F2 Setup" menu must be on.
Once a configuration file has been loaded, the data
loaded from the .DAT file is analyzed according to
the settings in the "F2 Setup" menu.
F7: Reset. Choosing this option resets the EVAL-CON-
TROL BOARD.
F10: Quit. This quits the AD7476/77 evaluation software
and returns control to the operating system.
INFORMATION WINDOWS
There are three information windows at the top of the main
screen. The left-hand window is the configuration window
and gives details about part being evaluated. It shows the
name of the program that has been downloaded to the EVAL-
CONTROL BOARD, the sampling frequency, the number
of bits, the analog input range of the part and the output code
format of the part. The right-hand large window is the Status
window. This window provides feedback to the user as to
what operations are currently being performed by the soft-
ware and also displays error messages. Directly underneath
the status window is a small window that shows the selected
conversion sequence and the maximum and minimum values
of the most recently captured samples for all channels in the
conversion sequence.
Test Mode
At the top right of the main screen are the Test Mode buttons.
These buttons determine what sort of testing is done on the
samples captured by the software. Both an ac analysis and dc
analysis can be performed. The function of these buttons are:
fft plot
Choosing this button causes the Digital Spectrum
Analyzer to appear at the bottom of the screen.
Histogram: Choosing this button causes the Histogram
Analyzer to be displayed at the bottom of the screen.
There is one other button near the top of the screen, beside
the "F10 Quit" button. This is:
blackman-harris: When performing a Fourier transform
of the sampled data, this button determines whether or not the
data is windowed by a blackman-harris window before the
transform. When this button is on, the data is windowed.
When this button is off, the data isn't windowed. See the
Digital Spectrum Analyzer section for more details.
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