Datasheet

AD7322 Data Sheet
Rev. B | Page 22 of 36
CONTROL REGISTER
The control register is used to select the analog input channel,
analog input configuration, reference, coding, and power mode.
The control register is a write-only, 12-bit register. Data loaded
on the DIN line corresponds to the AD7322 configuration for
the next conversion. Data should be loaded into the control
register after the range register has been initialized. The bit
functions of the control register are shown in Table 9 (the
power-up status of all bits is 0).
The two analog input channels can be configured as one pseudo
differential analog input, one true differential input, or two
single-ended analog inputs (see Table 10).
MSB LSB
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Write Zero Register Select Zero Zero ADD0 Mode 1 Mode 0 PM1 PM0 Coding Ref Seq1 Seq2 Zero 0
Table 9. Control Register Details
Bit Mnemonic Description
12, 11, 1 Zero These bits should contain 0 during each write to the control register.
10 ADD0
This channel address bit is used to select the analog input channel for the next conversion if the
sequencer is not being used. If the sequencer is being used, this channel address bit is used to select the
final channel in the consecutive sequence (see Table 10).
9, 8
Mode 1,
Mode 0
These two mode bits are used to select the configuration of the two analog input pins, V
IN
0 and V
IN
1.
These bits are used in conjunction with the channel address bit. On the AD7322, the analog inputs can be
configured as single-ended inputs, true differential inputs, or pseudo differential inputs (see Table 10).
7, 6 PM1, PM0 The power management bits are used to select different power mode options on the AD7322 (see Table 11).
5
Coding
This bit is used to select the type of output coding the AD7322 uses for the next conversion result. If
coding = 0, the output coding is twos complement. If coding = 1, the output coding is straight binary.
When operating in sequence mode, the output coding for each channel is the value written to the coding
bit during the last write to the control register.
4 Ref
The reference bit is used to enable or disable the internal reference. If Ref = 0, the external reference is
enabled and used for the next conversion, and the internal reference is disabled. If Ref = 1, the internal
reference is used for the next conversion. When operating in sequence mode, the reference used for each
channel is the value written to the Ref bit during the last write to the control register.
3, 2 Seq1, Seq2 The Sequence 1 and Sequence 2 bits are used to control the operation of the sequencer (see Table 12).
Table 10. Analog Input Configuration Selection
Mode 1 = 1, Mode 0 = 0 Mode 1 = 0, Mode 0 =1 Mode 1 = 0, Mode 0 = 0
Channel Address Bit Mode 1 = 1, Mode 0 = 1 1 Fully Differential Input 1 Pseudo Differential Input 2 Single-Ended Inputs
ADD0 V
IN
+ V
IN
− V
IN
+ V
IN
− V
IN
+ V
IN
− V
IN
+ V
IN
−
0 Not allowed V
IN
0 V
IN
1 V
IN
0 V
IN
1 V
IN
0 AGND
1 Not allowed V
IN
0 V
IN
1 V
IN
0 V
IN
1 V
IN
1 AGND