Texas Instruments ADS867 Series Manual page 45

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8.4.2.5 Auto Channel Enable with Reset (AUTO_RST)
The devices can be programmed to scan the input signal on all analog channels automatically by writing a valid
auto channel sequence with a reset (AUTO_RST, A000h) command in the command register, as explained in
Figure 100. As shown in
command or after reading the output data of the frame. However, in order to accurately acquire and convert the
input signal on the first selected channel in the next data frame, the command frame must be a complete frame
of 32 SCLK cycles.
The sequence of channels for the automatic scan can be configured by the AUTO SCAN sequencing control
register (01h to 02h) in the program register; see the
continuously cycle through the selected channels in ascending order, beginning with the lowest channel and
converting all channels selected in the program register. On completion of the sequence, the devices return to
the lowest count channel in the program register and repeat the sequence. The input voltage range for each
channel in the auto-scan sequence can be configured by setting the
registers.
Sample N
CS
SCLK 1 2 14
AUTO_RST Command ± A000h
SDI
SDO
The devices remain in AUTO_RST mode if no other valid command is executed and SDI is kept low (see the
Continued Operation in the Selected Mode (NO_OP)
command is executed again at any time during this mode of operation, then the sequence of the scanned
channels is reset. The devices return to the lowest count channel of the auto-scan sequence in the program
register and repeat the sequence. The timing diagram in
which channels 0 to 2 are selected in the auto sequence. For switching between AUTO_RST mode and
MAN_Ch_n mode; see the
Sample
N
CS
SCLK
SDI AUTO_RST xxxx
SDO Sample N Data
Based on Previous
Mode Setting
Figure 101. Device Operation Example in AUTO_RST Mode
Copyright © 2015, Texas Instruments Incorporated
Figure 100, the CS signal can be pulled high immediately after the AUTO_RST
CS can go high immediately after AUTO_RST
command or after reading frame data.
16 17
15 18 30 31
X
X X X
Data from Sample N
D13 D12 D1 D0
Figure 100. Enter AUTO_RST Mode Timing Diagram
Channel Sequencing Modes
Ch 0 Ch 1
Sample Sample
0000h xxxx
Ch 0 Data
AUTO_RST Mode
(Channels 0-2 are selected in sequence.)
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Program Register Map
Range Select Registers
Enters AUTO_RST mode on CS Rising Edge
st
Samples 1 Ch. of Auto-Ch Sequence
32 1 2
X X X X
section) during subsequent data frames. If the AUTO_RST
Figure 101 shows this behavior using an example in
section.
Ch 2
Sample
0000h xxxx AUTO_RST
Ch 1 Data
ADS8674 ADS8678
ADS8674, ADS8678
SBAS627 – JULY 2015
section. In this mode, the devices
of the program
Samples 2
Auto-Ch Sequence
16
14 15 29 30
Stays in AUTO_RST Mode if
SDI is Low in a Data Frame
st
Data from 1 Ch. of Seq.
Ch 0
Sample
xxxx 0000h
Ch 2 Data
AUTO_RST Mode
(Channel sequence restarted from
lowest count.)
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nd
Ch. of
32
xxxx
Ch 0 Data
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