EVAL-AD7327CB AD [Analog Devices], EVAL-AD7327CB Datasheet - Page 23

• Manufacturer Part Number: EVAL-AD7327CB
• Description: 500 kSPS, 8-Channel, Software-Selectable, True Bipolar Input, 12-Bit Plus Sign ADC
• Manufacturer: AD [Analog Devices]

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 AD7327 configuration for the next
conversion. If the sequence register is being used, data should be loaded into the control register after the range registers and the sequence
register have been initialized. The bit functions of the control register are shown in Table 9 (the power-up status of all bits is 0).
MSB
15
Write
Table 9. Control Register Details
Bit
12, 11, 10
9, 8
7, 6
5
4
3, 2
1
The eight analog input channels can be configured as seven pseudo differential analog inputs, four pseudo differential inputs, four true
differential inputs, or eight single-ended analog inputs.
Table 10. Analog Input Configuration Selection
Channel Address Bits
ADD2
0
0
0
0
1
1
1
1
14
Register
Select 1
ADD1
0
0
1
1
0
0
1
1
Mnemonic
ADD2, ADD1,
ADD0
Mode 1, Mode 0
PM1, PM0
Coding
Ref
Seq1, Seq2
ZERO
ADD0
0
1
0
1
0
1
0
1
13
Register
Select 2
Mode 1 = 1, Mode 0 = 1
7 Pseudo Differential I/Ps
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
12
ADD2
Temperature indicator
0
1
2
3
4
5
6
+
Description
These three channel address bits are used to select the analog input channel for the next conversion if the
sequencer is not being used. If the sequencer is being used, the three channel address bits are used to
select the final channel in a consecutive sequence.
These two mode bits are used to select the configuration of the eight analog input pins, V
pins are used in conjunction with the channel address bits. On the AD7327, the analog inputs can be
configured as eight single-ended inputs, four fully differential inputs, four pseudo differential inputs, or
seven pseudo differential inputs (see Table 10).
The power management bits are used to select different power mode options on the AD7327 (see Table 11).
This bit is used to select the type of output coding the AD7327 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.
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.
The Sequence 1 and Sequence 2 bits are used to control the operation of the sequencer (see Table 12).
A 0 should be written to this bit at all times.
11
ADD1
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
7
7
7
7
7
7
7
−
10
ADD0
9
Mode 1
Mode 1 = 1, Mode 0 = 0
4 Fully Differential I/Ps
V
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
IN
0
0
2
2
4
4
6
6
+
Rev. 0 | Page 23 of 36
8
Mode 0
V
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
IN
1
1
3
3
5
5
7
7
−
7
PM1
PM0
6
Mode 1 = 0, Mode 0 =1
4 Pseudo Differential I/Ps
V
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
IN
0
0
2
2
4
4
6
6
+
5
Coding
V
V
V
V
V
V
V
V
V
4
Ref
IN
IN
IN
IN
IN
IN
IN
IN
IN
1
1
3
3
5
5
7
7
−
3
Seq1
2
Seq2
Mode 1 = 0, Mode 0 = 0
8 Single-Ended I/Ps
V
V
V
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
IN
IN
IN
0
1
2
3
4
5
6
7
+
1
ZERO
IN
0 to V
AD7327
V
AGND
AGND
AGND
AGND
AGND
AGND
AGND
AGND
IN
IN
7. These
−
LSB
0
0