
AD9910
ADDITIONAL FEATURES
PROFILES
The AD9910 supports the use of profiles, which consist of a group
of eight registers containing pertinent operating parameters for
a particular operating mode. Profiles enable rapid switching
between parameter sets. Profile parameters are programmed via
the serial I/O port. Once programmed, a specific profile is
activated by means of three external pins (PROFILE<2:0>). A
particular profile is activated by providing the appropriate logic
levels to the profile control pins per Table 15.
Rev. 0 | Page 41 of 60
Table 15. Profile Control Pins
PROFILE<2:0>
000
001
010
011
100
101
110
111
Active Profile
0
1
2
3
4
5
6
7
There are two different parameter sets that the eight profile
registers can control depending on the operating mode of the
device. When RAM enable = 0, the profile parameters follow
the single tone profile format detailed in the Register Map and
Bit Descriptions section. When RAM enable = 1, they follow
the RAM profile format.
As an example of the use of profiles, consider an application for
implementing basic two-tone frequency shift keying (FSK). FSK
uses the binary data in a serial bit stream to select between two
different frequencies: a mark frequency (Logic 1) and a space
frequency (Logic 0). To accommodate FSK, the device operates
in single tone mode. The register, Single Tone Profile 0, is
programmed with the appropriate frequency tuning word for a
space. The register, Single Tone Profile 1, is programmed with
the appropriate frequency tuning word for a mark. Then, with
the PROFILE1 and PROFILE2 pins tied to Logic 0, the
PROFILE0 pin is connected to the serial bit stream. In this way,
the logic state of the PROFILE0 pin causes the appropriate mark
and space frequencies to be generated in accordance with the
binary digits of the bit stream.
I/O_UPDATE PIN
By default, the I/O_UPDATE pin is an input that serves as a
strobe signal to allow synchronous update of the device
operating parameters. For example, frequency, phase and
amplitude control words for the DDS may be programmed via
the serial I/O Port. However, the serial I/O Port is an
asynchronous interface, so programming of the device
operating parameters via the I/O port is not synchronized with
the internal timing. With the I/O_UPDATE pin, the user can
synchronize the application of certain programmed operating
parameters with external circuitry when new parameters are
programmed into the I/O registers. A rising edge on I/O_UPDATE
initiates transfer of the register contents to the internal workings
of the device. Alternatively, the transfer of programmed data
from the programming registers to the internal hardware can
be accomplished by changing the state of the profile pins.
AUTOMATIC I/O UPDATE
The AD9910 offers an option whereby the I/O update function
is asserted automatically rather than relying on an external signal
supplied by the user. This feature is enabled by setting the internal
I/O update active bit in Control Function Register 2 (CFR2).
When this feature is active, the I/O_UPDATE pin becomes
an output pin. It generates an active high pulse each time an
internal I/O update occurs. The duration of the pulse is
approximately 12 cycles of SYSCLK. This I/O update strobe
can be used to notify an external controller that the device
has generated an I/O update internally.
The repetition rate of the internal I/O Update is programmed
via the serial I/O port. There are two parameters that control
the repetition rate. The first consists of the two I/O update rate
control bits in CFR2. The second is the 32-bit word in the I/O
update rate register that sets the range of an internal counter.
The I/O update rate control bits establish a divide by 1, 2, 4, or 8
of a clock signal that runs at f
SYSCLK
. The output of the divider
clocks the aforementioned 32-bit internal counter. The
repetition rate of the I/O update is given by
f
f
A
Update
O
I
2
B
SYSCLK
_
/
=
where
A
is the value of the 2-bit word comprising the I/O
update rate control bits and
B
is the value of the 32-bit word
stored in the I/O update rate register. The default value of A is 0
and the value of B is 0xFFFF. If B is programmed to 0x0003 or
less, the I/O_UPDATE pin no longer pulses, but assumes a
static Logic 1 state.
POWER-DOWN CONTROL
The AD9910 offers the ability to independently power down
four specific sections of the device. Power-down functionality
applies to the
Digital core
DAC
Auxiliary DAC
Input REFCLK clock circuitry
A power-down of the digital core disables the ability to update
the serial I/O port. However, the digital power-down bit can
still be cleared via the serial port to prevent the possibility of a
non-recoverable state.
Software power-down is controlled via four independent
power-down bits in Control Function Register 1 (CFR1).