AD9835
Table I. Control Registers
Register
FREQ0 REG
FREQ1 REG
PHASE0 REG
PHASE1 REG
PHASE2 REG
PHASE3 REG
Size
32 Bits
32 Bits
12 Bits
12 Bits
12 Bits
12 Bits
Description
Frequency Register 0. This de-
fines the output frequency, when
FSELECT = 0, as a fraction of the
MCLK frequency.
Frequency Register 1. This de-
fines the output frequency, when
FSELECT = 1, as a fraction of the
MCLK frequency.
Phase Offset Register 0. When
PSEL0 = PSEL1 = 0, the contents
of this register are added to the
output of the phase accumulator.
Phase Offset Register 1. When
PSEL0 = 1 and PSEL1 = 0, the con-
tents of this register are added to the
output of the phase accumulator.
Phase Offset Register 2. When
PSEL0 = 0 and PSEL1 = 1, the
contents of this register are added to
the output of the phase accumulator.
Phase Offset Register 3. When
PSEL0 = PSEL1 = 1, the contents
of this register are added to the
output of the phase accumulator.
Table II. Addressing the Registers
A3 A2
A1
A0
Destination Register
0
0
0
0
FREG0 REG 8 L LSBs
0
0
0
1
FREG0 REG 8 H LSBs
0
0
1
0
FREG0 REG 8 L MSBs
0
0
1
1
FREG0 REG 8 H MSBs
0
1
0
0
FREG1 REG 8 L LSBs
0
1
0
1
FREG1 REG 8 H LSBs
0
1
1
0
FREG1 REG 8 L MSBs
0
1
1
1
FREG1 REG 8 H MSBs
1
0
0
0
PHASE0 REG 8 LSBs
1
0
0
1
PHASE0 REG 8 MSBs
1
0
1
0
PHASE1 REG 8 LSBs
1
0
1
1
PHASE1 REG 8 MSBs
1
1
0
0
PHASE2 REG 8 LSBs
1
1
0
1
PHASE2 REG 8 MSBs
1
1
1
0
PHASE3 REG 8 LSBs
1
1
1
1
PHASE3 REG 8 MSBs
Table III. 32-Bit Frequency Word
16 MSBs
8 H MSBs 8 L MSBs
16 LSBs
8 H LSBs 8 L LSBs
Table IV. 12-Bit Frequency Word
4 MSBs (The 4 MSBs of the
8-Bit Word Loaded = 0)
8 LSBs
Table V. Commands
C3 C2 C1 C0
0 000
0 001
0 010
0 011
0 100
0 101
0 110
0 111
Command
Write 16 Phase bits (Present 8 Bits + 8 Bits
in Defer Register) to Selected PHASE
REG.
Write 8 Phase bits to Defer Register.
Write 16 Frequency bits (Present 8 Bits
+ 8 Bits in Defer Register) to Selected
FREQ REG.
Write 8 Frequency bits to Defer Register.
Bits D9 (PSEL0) and D10 (PSEL1) are
used to Select the PHASE REG when
SELSRC = 1. When SELSRC = 0, the
PHASE REG is selected using the pins
PSEL0 and PSEL1 Respectively.
Bit D11 is used to select the FREQ REG
when SELSRC = 1. When SELSRC = 0,
the FREQ REG is selected using the pin
FSELECT.
This command is used to control the
PSEL0, PSEL1 and FSELECT bits
using only one write. Bits D9 and D10
are used to select the PHASE REG and
Bit 11 is used to select the FREQ REG
when SELSRC = 1. When SELSRC = 0,
the PHASE REG is selected using the
pins PSEL0 and PSEL1 and the FREQ
REG is selected using the pin FSELECT.
Reserved. Configures the AD9835 for
Test Purposes.
Table VI. Controlling the AD9835
D15 D14 Command
1 0 Selects source of Control for the PHASE and
FREQ Registers and Enables Synchronization. Bit
D13 is the SYNC Bit. When this bit is High, read-
ing of the FSELECT, PSEL0 and PSEL1 bits/pins
and the loading of the Destination Register with
data is synchronized with the rising edge of MCLK.
The latency is increased by 2 MCLK cycles when
SYNC = 1. When SYNC = 0, the loading of the
data and the sampling of FSELECT/PSEL0/PSEL1
occurs asynchronously. Bit D12 is the Select
Source Bit (SELSRC). When this bit Equals 1, the
PHASE/FREQ REG is Selected using the bits
FSELECT, PSEL0 and PSEL1. When SELSRC =
0, the PHASE/FREQ REG is Selected using the
pins FSELECT, PSEL0 and PSEL1.
1 1 Sleep, Reset and Clear. D13 is the SLEEP bit. When
this bit equals 1, the AD9835 is powered down, inter-
nal clocks are disabled and the DAC's current sources
and REFOUT are turned off. When SLEEP = 0, the
AD9835 is powered up. When RESET (D12) = 1,
the phase accumulator is set to zero phase which
corresponds to an analog output of full scale. When
CLR (D11) = 1, SYNC and SELSRC are set to
zero. CLR automatically resets to zero.
–6–
REV. 0