Analog Devices EVAL-AD7761FMCZ User Manual page 16

UG-949
Registers Tab
The Registers tab allows precise control of the
registers, allowing them to be read back and written to. The
registers are grouped together and can be altered in a number of
ways, as shown in Figure 22. The register to be written to can be
selected from the register map, located on the left hand side of
the Registers tab. Individual register bits can be changed from
the register section, or the entire register can also be written to
by writing the required hexadecimal value. Drop-down options
can be selected from the Bitfields section, or the entire bit field
can be written to with a hexadecimal value.
A particular register configuration can be saved to be loaded
again at a later time.
Figure 22. Registers Tab
Precharge Buffers: Register Operation
The precharge buffers operate differently than the other registers.
To change these registers, it is recommended to navigate to the
Registers tab, select Precharge Buffer 1 or Precharge Buffer 2
from the register map, and change the value of these registers
using the hexadecimal value located on the right hand side of
the Register section (see Figure 23). The software reads back the
status of the registers correctly; however, to change a bit to 0, for
example, a 1 must be written to the given bit in the register. See
the AD7761 data sheet for more details.
Figure 23. Enabling/Disabling the Precharge Buffers
Exiting the Software
To exit the software, click the red X at the top right hand corner
of the main window. Be sure to press the reset button before the
EVAL-SDP-CH1Z is powered off.
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Example
AD7761 In this example, a sample is taken and analyzed with the help of
the AD7761
the ADC.
The following equipment is required:
To sample and analyze the data, take the following steps:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10. The sampled data is now present in the data capture tabs
11. Under the FFT tab, the FFT analysis displays results similar
Rev. 0 | Page 16 of 17
EVAL-AD7761FMCZ User Guide
software. The desired data is expected on Channel 2 of
•
Audio Precision source (AP SYS-2722 or similar high
precision source)
•
A PC
•
EVAL-AD7761FMCZ evaluation board
•
EVAL-SDP-CH1Z SDP-H1 controller board
•
12 V power supply for the EVAL-SDP-CH1Z
•
9 V power supply for the EVAL-AD7761FMCZ
Connect the evaluation board to the SDP-H1 board.
Set both LK1 and LK2 to Position B on the evaluation
board.
Power up both boards, and then connect the SDP-H1
board to the PC via the USB cable supplied.
Start the AD7761 evaluation software. Wait for the Busy
indicator to turn off.
Configure the Audio Precision source to the following
settings, and connect the output to the Channel 2 input, as
follows:
•
Select a sine wave output and High Acc
•
Set the output to balanced float
•
Set the frequency to 1 kHz
•
Set the amplitude to 7.734 V p-p
If not using the default configuration ensure that MCLK (Hz)
and Ext. REF (V) on the software configuration tab are set
to match the clock frequency and reference voltage supplied
to the chip (by default, 32.768 MHz and 4.096 V).
Set the number of samples per channel to 32,768 (default).
Configure the registers as required using the pop-up
menus under the Configuration tab. For this example, the
settings are wideband filter, decimation by 32, fast power
mode, and MCLK divide by four (all default).
Click Sample to take a reading. Wait for the Busy indicator
to turn off.
(Waveform, FFT, and Histogram tabs). Change between
each of these to view the results. In this case, select
Channel 2 on the channel enable and disable check boxes
to view the desired data on Channel 2.
to the following:
•
SNR = 96.7 dB
•
THD = −120 dB
•
SINAD = 97.6 dB
•
Fund. Frequency = 1000 Hz
•
Fund. Amplitude = −0.5 dBFS