Data Sheet

AD9959

Rev. C | Page 41 of 44

DESCRIPTIONS FOR CHANNEL REGISTERS

Channel Function Register (CFR)—Address 0x03

Three bytes are assigned to this register.

Table 34. Bit Descriptions for CFR

Bit

Mnemonic

Description

23:22

Amplitude frequency

phase (AFP) select

Controls what type of modulation is to be performed for that channel. See the Modulation Mode section

for details.

21:16

Open

15

Linear sweep no-dwell

0 = the linear sweep no-dwell function is inactive (default).

1 = the linear sweep no-dwell function is active. If CFR[15] is active, the linear sweep no-dwell function is

activated. See the Linear Sweep Mode section for details. If CFR[14] is clear, this bit is don’t care.

14

Linear sweep enable

0 = the linear sweep capability is inactive (default).

1 = the linear sweep capability is enabled. When enabled, the delta frequency tuning word is applied to

the frequency accumulator at the programmed ramp rate.

13

Load SRR at

I/O_UPDATE

0 = the linear sweep ramp rate timer is loaded only upon timeout (timer = 1) and is not loaded because

of an I/O_UPDATE input signal (default).

1 = the linear sweep ramp rate timer is loaded upon timeout (timer = 1) or at the time of an I/O_UPDATE

input signal.

12:11

Open

10

Must be 0

Must be set to 0.

9:8

DAC full-scale current

control

11 = the DAC is at the largest LSB value (default).

See Table 5 for other settings.

7

Digital power-down

0 = the digital core is enabled for operation (default).

1 = the digital core is disabled and is in its lowest power dissipation state.

6

DAC power-down

0 = the DAC is enabled for operation (default).

1 = the DAC is disabled and is in its lowest power dissipation state.

5

Matched pipe delays

0 = matched pipe delay mode is inactive (default).

active

1 = matched pipe delay mode is active. See the Single-Tone Mode—Matched Pipeline Delay section for

details.

4

Autoclear sweep

accumulator

0 =

the current state of the sweep accumulator is not impacted by receipt of an I/O_UPDATE signal

(default).

1 = t

he sweep accumulator is automatically and synchronously cleared for one cycle upon receipt

of an I/O_UPDATE signal.

3

Clear sweep

0 = the sweep accumulator functions as normal (default).

accumulator

1 = the sweep accumulator memory elements are asynchronously cleared.

2

Autoclear phase

accumulator

0 = t

he current state of the phase accumulator is not impacted by receipt of an I/O_UPDATE signal

(default).

1 = t

he phase accumulator is automatically and synchronously cleared for one cycle upon receipt

of an I/O_UPDATE signal.

1

Clear phase

0 = the phase accumulator functions as normal (default).

accumulator

1 = the phase accumulator memory elements are asynchronously cleared.

0

Sine wave output

0 = the angle-to-amplitude conversion logic employs a cosine function (default).

enable

1 = the angle-to-amplitude conversion logic employs a sine function.