AD9910 Analog Devices, AD9910 Datasheet - Page 10

• Manufacturer Part Number: AD9910
• Description: 3.3V CMOS Direct Digital Synthesizer
• Manufacturer: Analog Devices

PRELIMINARY TECHNICAL DATA
MODES OF OPERATION
The AD9910 has four modes of operation.
1) Single-tone mode
2) RAM modulation mode
3) Linear ramp modulation mode
4) Parallel data port modulation mode
The modes relate to the data source used to supply the DDS
with its signal control parameters: frequency, phase, and ampli-
tude. The partitioning of the data into different combinations
of frequency, phase, and amplitude is handled automatically
based on the mode and/or specific control bits.
In single-tone mode, data is routed to the DDS directly from the
programming registers. In RAM modulation mode, data is
routed to the DDS directly from the contents of the RAM. In
linear ramp modulation mode, data is routed to the DDS from a
digital ramp generator. In parallel data port modulation mode,
data is routed to the DDS directly from the parallel data port.
NOTE: The various modulation modes generally operate on only
one of the DDS signal control parameters (two in the case of the
polar modulation format). The static (i.e., unmodulated) DDS
signal control parameters are stored in their appropriate pro-
gramming registers and automatically routed to the DDS based
on the selected mode.
A separate output shift keying (OSK) function is also available.
Figure 4: Single-tone mode
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This function employs a separate digital linear ramp generator
that only affects the DDS's amplitude parameter. As such, the
OSK function can not be used when one of the modulation
modes is operating on the DDS's amplitude parameter.
SINGLE-TONE MODE
In single-tone mode (Figure 4), the three DDS signal control
parameters are supplied directly from the programming regis-
ters. The device can be programmed to operate with or without
profiles. A profile is an independent register that contains the
three DDS signal control parameters. There are eight available
Profile Registers.
When programmed to operate with parameter profiles, each
profile can be accessed independently. A particular profile is
made selected via the three external Profile Select Pins. A
change in the state of the Profile Select Pins along with the next
rising edge of Sync Clock updates the DDS with the parameters
specified by the selected profile.
NOTE: When the OSK function is enabled, its amplitude data
overrides the amplitude parameter stored in the Profile Registers.
When programmed to operate without profiles the three DDS
signal control parameters reside in separate registers. Fre-
quency is controlled via the FTW register. Phase offset is con-
trolled via the POW register. Amplitude is controlled via the
amplitude scale factor that resides in the ASF register.
AD9910