Datasheet

AD5735 Data Sheet
Rev. C | Page 32 of 48
DATA REGISTERS
The input shift register is 24 bits wide. When PEC is enabled,
the input shift register is 32 bits wide, with the last eight bits
corresponding to the PEC code (see the Packet Error Checking
section for more information about PEC). When writing to a
data register, the format shown in Table 11 must be used.
DAC Data Register
When writing to a DAC data register, Bit D15 to Bit D4 are the
DAC data bits. Table 13 shows the register format, and Table 12
describes the functions of Bit D23 to Bit D16.
Table 11. Input Shift Register for a Write Operation to a Data Register
MSB LSB
D23 D22 D21 D20 D19 D18 D17 D16 D15 to D0
R/
W
DUT_AD1 DUT_AD0 DREG2 DREG1 DREG0 DAC_AD1 DAC_AD0 Data
Table 12. Descriptions of Data Register Bits[D23:D16]
Bit Name Description
R/
W
This bit indicates whether the addressed register is written to or read from.
0 = write to the addressed register.
1 = read from the addressed register.
DUT_AD1, DUT_AD0 Used in association with the external pins AD1 and AD0, these bits determine which AD5735 device is being
addressed by the system controller. It is not recommended to tie both AD1 and AD0 low when using PEC, see
the Packet Error Checking section.
DUT_AD1 DUT_AD0 Part Addressed
0 0 Pin AD1 = 0, Pin AD0 = 0
0 1 Pin AD1 = 0, Pin AD0 = 1
1 0 Pin AD1 = 1, Pin AD0 = 0
1 1 Pin AD1 = 1, Pin AD0 = 1
DREG2, DREG1, DREG0 These bits select the register to be written to. If a control register is selected (DREG[2:0] = 111), the CREG bits in
the control register select the specific control register to be written to (see Table 20).
DREG2 DREG1 DREG0 Function
0 0 0 Write to DAC data register (one DAC channel)
0 0 1 Reserved
0
1
0
Write to gain register (one DAC channel)
0 1 1 Write to gain registers (all DAC channels)
1 0 0 Write to offset register (one DAC channel)
1 0 1 Write to offset registers (all DAC channels)
1 1 0 Write to clear code register (one DAC channel)
1 1 1 Write to a control register
DAC_AD1, DAC_AD0 These bits are used to specify the DAC channel. If a write to the part does not apply to a specific DAC channel,
these bits are don’t care bits.
DAC_AD1 DAC_AD0 DAC Channel
0 0 DAC A
0 1 DAC B
1 0 DAC C
1 1 DAC D
Table 13. Programming the DAC Data Register
D23 D22 D21 D20 D19 D18 D17 D16 D15 to D4 D3 to D0
R/
W
DUT_AD1 DUT_AD0 0 0 0 DAC_AD1 DAC_AD0 DAC data X
1
1
X = don’t care.