Datasheet

AD7923 Data Sheet
Rev. D | Page 12 of 24
CONTROL REGISTER DESCRIPTIONS
The control register on the AD7923 is a 12-bit, write-only
register. Data is loaded from the DIN pin of the AD7923 on the
falling edge of SCLK. The data is transferred on the DIN line at
the same time that the conversion result is read from the part.
The data transferred on the DIN line corresponds to the
AD7923 configuration for the next conversion. This requires
16 serial clocks for every data transfer. Only the information
provided on the first 12 falling clock edges (after
CS
falling
edge) is loaded to the control register. MSB denotes the first bit
in the data stream. The bit functions are outlined in Table 5.
Table 5. Control Register Bit Functions
MSB LSB
WRITE SEQ1 DONTC DONTC ADD1 ADD0 PM1 PM0 SEQ0 DONTC RANGE CODING
Table 6.
Bit Name Description
11
WRITE
The value written to this bit of the control register determines whether the following 11 bits are loaded to the
control register. If this bit is a 1, the following 11 bits are written to the control register. If it is a 0, the remaining
11 bits are not loaded to the control register and it remains unchanged.
10 SEQ1 The SEQ1 bit in the control register is used with the SEQ0 bit to control the use of the sequencer function (see
Table 9).
7–6 ADD1
ADD0
These two address bits are loaded at the end of the present conversion and select which analog input channel is
converted in the next serial transfer, or they can also be used to select the final channel in a consecutive sequence,
as described in Table 9. The selected input channel is decoded, as shown in Table 7. The next channel to be
converted on is selected by the mux on the 14th SCLK falling edge. Channel address bits corresponding to the
conversion result are also output on the DOUT serial data stream prior to the 12 bits of data (see the Serial Interface
section).
5, 4 PM1
PM0
Power management bits. These two bits decode the mode of operation of the AD7923, as shown in Table 8.
3 SEQ0 The SEQ0 bit in the control register is used with the SEQ1 bit to control the use of the sequencer function.
(see Table 9).
2, 9–8 DONTC Don’t care.
1 RANGE This bit selects the analog input range to be used on the AD7923. If it is set to 0, the analog input range extends from
0 V to 2 × REF
IN
. If it is set to 1, the analog input range extends from 0 V to REF
IN
(for the next conversion). For the 0 V
to 2 × REF
IN
range, AV
DD
= 4.75 V to 5.25 V.
0 CODING This bit selects the type of output coding the AD7923 uses for the conversion result. If this bit is set to 0, the output
coding for the part is twos complement. If this bit is set to 1, the output coding from the part is straight binary (for
the next conversion).
Table 7. Channel Selection
ADD1 ADD0 Analog Input Channel
0 0 V
IN
0
0 1 V
IN
1
1 0 V
IN
2
1 1 V
IN
3