Analog Devices EVAL-AD9959 User Manual page 14

User Guide
EVALUATION BOARD SOFTWARE
Note that when performing linear frequency/amplitude sweeps, the
Enable ASF box must be left unchecked.
When using the RU/RD feature, the Enable Auto ASF box must
be checked. Once the Enable Auto ASF box has been checked,
the Amplitude Ramp Rate, Amplitude Step Adjust, and the Load
ARR @ I/O Update options are available (see
Figure 25.
Use the Amplitude Ramp Rate box to set the Amplitude Ramp
Rate (ARR) time. This time (entered in µs) can range from a
× 1
minimum value of:
1
SYNC CLK
to a maximum value of:
1
SYNC CLK
× 2
8 bits of output ramp rate resolution − 1
This implies that if the system clock is 500 MHz, the ARR value
can range from 8 ns (minimum) to 2.040 µs (maximum). If the value
entered exceeds the maximum time, then a pop-up window
26) alerts the user that the value entered will be changed to the
appropriate maximum value.
Figure 26.
In the Amplitude Step Adjust box, select the amplitude scale
factor step size. The default setting of this box is 1, indicating that
step size will be 1 LSB. A selection of 8 means the step size will be
8 LSB.
Select Load ARR @ I/O Update to load the contents of the
amplitude ramp rate register into the amplitude ramp rate timer
every time an I/O_UPDATE is sent to the device.
2. Profile Registers
The AD9959 features up to 16 programmable registers per channel
as shown in Figure 23. Due to certain channel constraints, however,
there are limitations on how the Profile Registers can be used
in some configurations as described in the Channel Constraint
Guidelines section of the AD9959 data sheet.
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Use the Profile Registers to enter the information needed for mod-
ulation (FSK, PSK, or ASK) and linear sweep modes of operation.
Upon default, the Profile Registers are configured for frequency
inputs, but these registers can be changed to intake phase or
amplitude information by selecting the desired modulation type in
the Modulation Output Type box in the Channel Control window.
Figure 25).
Figure 27
modulation (PSK) is selected.
(3)
When the channel is in the modulation or linear sweep mode of
operation, input the starting frequency in the Frequency 00 box,
starting phase in the Phase Offset box, and the starting amplitude
(4)
in the Enable ASF box. In modulation mode, use the Profile Reg-
isters to input frequency, phase, or amplitude information for the
level of modulation selected. For instance, if 4-level frequency mod-
ulation is selected, input the starting frequency in the Frequency
00 box, second frequency in the Frequency 01 box, third frequency
(Figure
in the Frequency 02 box, and fourth frequency in the Frequency
03 box. An example of using the Profile Registers for 2-level
frequency modulation is shown in
the frequency starts at 10 MHz and ramps up to 50 MHz.
In the linear sweep mode of operation, only the first Profile Regis-
ter box (Frequency 01, Phase 01, or Amplitude 01) is used. It
indicates the ending point of the sweep. In
linear sweep begins at 10 MHz and ends at 50 MHz.
EVAL-AD9959
shows how the Profile Registers appear when phase
Figure 27.
Figure
Figure 28.
28. In this configuration,
Figure 28, the frequency
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