SBAS582C – JULY 2014 – REVISED APRIL 2015
8.5 Register Maps
The internal registers of the ADS8684 and ADS8688 are categorized into two categories: command registers and
program registers.
The command registers are used to select the channel sequencing mode (AUTO_RST or MAN_Ch_n), configure
the device in standby (STDBY) or power-down (PWR_DN) mode, and reset (RST) the program registers to their
default values.
The program registers are used to select the sequence of channels for AUTO_RST mode, select the SDO output
format, and control input range settings for individual channels.
8.5.1 Command Register Description
The command register is a 16-bit, write-only register that is used to set the operating modes of the ADS8684 and
ADS8688. The settings in this register are used to select the channel sequencing mode (AUTO_RST or
MAN_Ch_n), configure the device in standby (STDBY) or power-down (PWR_DN) mode, and reset (RST) the
program registers to their default values. All command settings for this register are listed in
. During
power-up or reset, the default content of the command register is all 0's and the device waits for a command to
be written before being placed into any mode of operation. Refer to
for a typical timing diagram for
writing a 16-bit command into the device. The device executes the command at the end of this particular data
frame when the CS signal goes high.
Table 6. Command Register Map
MSB BYTE
LSB BYTE
COMMAND
REGISTER
OPERATION IN NEXT FRAME
(Hex)
B15
B14
B13
B12
B11
B10
B9
B8
B[7:0]
Continued Operation
0
0
0
0
0
0
0
0
0000 0000
0000h
Continue operation in previous mode
(NO_OP)
Standby
1
0
0
0
0
0
1
0
0000 0000
8200h
Device is placed into standby mode
(STDBY)
Power Down
1
0
0
0
0
0
1
1
0000 0000
8300h
Device is powered down
(PWR_DN)
Reset program registers
1
0
0
0
0
1
0
1
0000 0000
8500h
Program register is reset to default
(RST)
Auto Ch. Sequence with Reset
1
0
1
0
0
0
0
0
0000 0000
A000h
Auto mode enabled following a reset
(AUTO_RST)
Manual Ch 0 Selection
1
1
0
0
0
0
0
0
0000 0000
C000h
Channel 0 input is selected
(MAN_Ch_0)
Manual Ch 1 Selection
1
1
0
0
0
1
0
0
0000 0000
C400h
Channel 1 input is selected
(MAN_Ch_1)
Manual Ch 2 Selection
1
1
0
0
1
0
0
0
0000 0000
C800h
Channel 2 input is selected
(MAN_Ch_2)
Manual Ch 3 Selection
1
1
0
0
1
1
0
0
0000 0000
CC00h
Channel 3 input is selected
(MAN_Ch_3)
Manual Ch 4 Selection
1
1
0
1
0
0
0
0
0000 0000
D000h
Channel 4 input is selected
(MAN_Ch_4)
(1)
Manual Ch 5 Selection
1
1
0
1
0
1
0
0
0000 0000
D400h
Channel 5 input is selected
(MAN_Ch_5)
Manual Ch 6 Selection
1
1
0
1
1
0
0
0
0000 0000
D800h
Channel 6 input is selected
(MAN_Ch_6)
Manual Ch 7 Selection
1
1
0
1
1
1
0
0
0000 0000
DC00h
Channel 7 input is selected
(MAN_Ch_7)
Manual AUX Selection
1
1
1
0
0
0
0
0
0000 0000
E000h
AUX channel input is selected
(MAN_AUX)
(1)
Shading indicates bits or registers not included in the 4-channel version of the device.
8.5.2 Program Register Description
The program register is a 16-bit register used to set the operating modes of the ADS8684 and ADS8688. The
settings in this register are used to select the channel sequence for AUTO_RST mode, configure the device ID in
daisy-chain mode, select the SDO output format, and control input range settings for individual channels. All
program settings for this register are listed in
. During power-up or reset, the different program registers in
the device wake up with their default values and the device waits for a command to be written before being
placed into any mode of operation.
Copyright © 2014–2015, Texas Instruments Incorporated
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