PRELIMINARY TECHNICAL DATA

AD9910

Rev. PrD| Page 10 of 13

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.

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.

Figure 4: Single-tone mode