Analog Devices EVAL-CN-304-SDZ, Руководство пользователя

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EVAL-CN-304-SDZ Evaluation Board User Guide UG-266
Rev. B | Page 5 of 12
OPERATING THE SOFTWARE
Select External MCLK Frequency
Having selected the digital interface specifics, next use the
MCLK box to choose which frequency to use. The boards are
supplied with a 75 MHz general oscillator. If a different clock
source is required, the CLK1 SMB connector can be used to
supply a different MCLK value.
Two options for the general oscillator include the AEL3013
oscillators from AEL Crystals and the SG-310SCN oscillators
from Epson Electronics.
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005
Figure 5. MCLK Input
Programming Method: Hardware or Software
Functions that select frequency and phase registers, reset internal
registers, and power down the DAC can be implemented by
using either software or hardware. Click
Software or Hardware
to select the programming method (see Figure 6). By choosing
hardware, the appropriate hardware control pins are used to
control these functions. By choosing software, the appropriate
software control bits are used to control these functions.
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006
Figure 6. Programming Method
Loading Frequency and Phase Registers
The desired output frequency and output phase can be loaded
using the inputs shown in Figure 7. Either the
FREQ 0 register or
the FREQ 1 register can be loaded with frequency data. The
frequency data is loaded in megahertz, and the equivalent
hexadecimal code is shown to the right once data is entered; press
Enter to load the data. When data is loaded, the output appears on
the IOUT and IOUTB pins. Similarly, select either the PHASE 0
register or the PHASE 1 register and the phase data loads in
degrees.
The analog output frequency from the
AD9834 is defined by
f
MCLK
/2
28
× FREQREG
where FREQREG is the value loaded into the selected frequency
register in decimals. This signal is phase shifted by
2π/4096 × PHASEREG
where
PHASEREG
is the value contained in the selected phase
register in decimals.
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007
Figure 7. Frequency and Phase Load
FSK and PSK Functionality
In software mode, the AD9834 can be set up for FSK or PSK
functionality by entering the bit rate in milliseconds and by
clicking the
PSK or FSK button (see Figure 8).
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008
Figure 8. FSK and PSK Functionality