Datasheet

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(1)
DRDY
CS
SCLK
DOUT
DIN
(holdinactive)
StatusByte
(2)
DataByte1(MSB) DataByte2(LSB)
(3)
CS
SCLK
DIN
CommandByte1
Don'tCare
Don'tCare
(1)
DOUT Don'tCare
Data
(2)
Data
(2)
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ADS1158
www.ti.com SBAS429D –JUNE 2008– REVISED MARCH 2011
Channel Data Read Command
Concurrent with the first SCLK transition, channel
data are output on the DOUT output pin. A total of 16
To read channel data in this mode (register format),
or 24 SCLK transitions complete the data read
the first three bits of the command byte to be shifted
operation. The number of shifts depend on whether
into the device are 001. The MUL bit must be set
the status byte is enabled. The data must be
because this command is a multiple byte read. The
completely shifted out before the next occurrence of
remaining bits are don’t care but must be clocked to
DRDY or the remaining data are corrupted. It is
the device. During this time, ignore any data that
recommended to monitor DRDY to synchronize the
appear on DOUT until the command completes.
start of the read operation to avoid data corruption.
These data should be ignored. Beginning with the
Before DRDY asserts low, the MSB of the Status byte
eighth SCLK falling edge (command byte completed),
or the MSB of the data are output on DOUT (CS =
the MSB of the channel data are restarted on DOUT.
'0'), as shown in Figure 44. In this format, reading the
The user clocks the data on the following rising edge
data a second time within the same DRDY frame
of SCLK. A total of 32 SCLK transitions complete the
returns data = 0.
data read operation. Unlike the direct read mode, the
channel data can be read during a DRDY transition
COMMAND DESCRIPTION
without data corruption. This mode is recommended
when DRDY is not used and the data are polled to
Commands may be sent to the ADS1158 with CS tied
detect for the occurrence of new data or when CS is
low. However, after the Channel Data Read Direct
tied low to avoid the necessity for an SPI timeout that
operation, it is necessary to toggle CS or an SPI
otherwise occurs when reading data directly. This
timeout must occur to reset the interface before
option avoids conflicts with DRDY, as shown in
sending a command.
Figure 45.
(1) No SCLK activity.
(2) Optional for Auto-Scan mode, disabled for Fixed-Channel mode. See Table 12, Status Byte.
(3) After the channel data read operation, CS must be toggled or an SPI timeout must occur before sending commands.
Figure 44. Channel Data Read Direct (No Command)
(1) After the prescribed number of registers are read, then one or more additional commands can be issued in succession.
(2) Three bytes for channel data register read. See Table 12, Status Byte. One or more bytes for register read, depending on MUL bit.
Figure 45. Register and Channel Data (Register Format) Read
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