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AUTO_RST
Sample
N
SCLK
SDI
SDO
CS
xxxx
Sample N Data
Ch 0
Sample
0000h
xxxx
Ch 0 Data
Ch 1
Sample
0000h
xxxx
Ch 1 Data
Ch 2
Sample
AUTO_RST
xxxx
Ch 2 Data
Based on Previous
Mode Setting
Ch 0
Sample
0000h
xxxx
Ch 0 Data
AUTO_RST Mode
(Channel sequence restarted from
lowest count.)
AUTO_RST Mode
(Channels 0-2 are selected in sequence.)
1
2
14
15
16
17
18
32
33
34
SCLK
CS
D3
SDO
Data from Sample N
D17
D16
D2
D1
D0
AUTO_RST Command
±
A000h
SDI
X
X
X
X
X
X
X
X
Sample N
Enters AUTO_RST Mode on CS Rising Edge
Samples 1
st
Ch. of Auto-Ch Sequence
CS can go high immediately after AUTO_RST
command or after reading frame data.
1
2
14
15
16
Stays in AUTO_RST Mode if
SDI is Low in a Data Frame
33
34
Samples 2
nd
Ch. of
Auto-Ch Sequence
Data from 1
st
Ch of Seq.
SBAS686 – JULY 2015
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
. As shown in
, the CS signal can be pulled high immediately after the AUTO_RST 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 34 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
section. In this mode, the devices
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
of the program
registers.
Figure 84. Enter AUTO_RST Mode Timing Diagram
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)
section) during subsequent data frames. If the AUTO_RST
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
shows this behavior using an example 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
section.
Figure 85. Device Operation Example in AUTO_RST Mode
Copyright © 2015, Texas Instruments Incorporated
43
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