Datasheet

DIN
SCLK
0000001X
(STANDBY)
Operating StandbyMode Operating
0000000X
(WAKEUP)
ADS1281
www.ti.com SBAS378D –AUGUST 2007–REVISED JUNE 2010
WAKEUP: Wake-Up From Standby Mode SDATAC: Stop Read Data Continuous
Description: This command is used to exit the Description: This command stops the Read Data
standby mode. Upon sending the command, the time Continuous mode. Exiting the Read Data Continuous
for the first data to be ready is illustrated in Figure 41 mode is required before sending Register and Data
and Table 14. Sending this command during normal read commands. This command suppresses the
operation has no effect; for example, reading data by DRDY output, but the ADS1281 continues
the Read Data Continuous method with DIN held low. conversions.
STANDBY: Standby Mode RDATA: Read Data By Command
Description: This command places the ADS1281 Description: This command reads the conversion
into Standby mode. In Standby, the device enters a data. See the Read Data By Command section for
reduced power state where a low quiescent current more details.
remains to keep the register settings and SPI
RREG: Read Register Data
interface active. For complete device shutdown, take
the PWDN pin low (register settings are not saved).
Description: This command is used to read single or
To exit Standby mode, issue the WAKEUP command.
multiple register data. The command consists of a
The operation of Standby mode is shown in
two-byte op-code argument followed by the output of
Figure 53.
register data. The first byte of the op-code includes
the starting address, and the second byte specifies
the number of registers to read – 1.
First command byte: 001r rrrr, where rrrrr is the
starting address of the first register.
Second command byte: 000n nnnn, where nnnnn is
the number of registers – 1 to read.
Starting with the 16th falling edge of SCLK, the
register data appear on DOUT.
Figure 53. STANDBY Command Sequence
The RREG command is illustrated in Figure 54. Note
that a delay of 24 f
CLK
cycles is required between
SYNC: Synchronize the A/D Conversion
each byte transaction.
Description: This command synchronizes the A/D
WREG: Write to Register
conversion. Upon receipt of the command, the
reading in progress is cancelled and the conversion
Description: This command writes single or multiple
process is re-started. In order to synchronize multiple
register data. The command consists of a two-byte
ADS1281s, the command must be sent
op-code argument followed by the input of register
simultaneously to all devices. Note that the SYNC pin
data. The first byte of the op-code contains the
must be high for this command.
starting address and the second byte specifies the
number of registers to write – 1.
RESET: Reset the Device
First command byte: 001r rrrr, where rrrrr is the
Description: The RESET command resets the
starting address of the first register.
registers to default values, enables the Read Data
Continuous mode, and restarts the conversion
Second command byte: 000n nnnn, where nnnnn is
process; the RESET command is functionally the
the number of registers – 1 to write.
same as the RESET pin. See Figure 40 for the
RESET command timing.
Data byte(s): one or more register data bytes,
depending on the number of registers specified.
RDATAC: Read Data Continuous
Figure 55 illustrates the WREG command.
Description: This command enables the Read Data
Continuous mode (default mode). In this mode,
Note that a delay of 24 f
CLK
cycles is required
conversion data can be read from the device directly
between each byte transaction.
without the need to supply a data read command.
Each time DRDY falls low, new data are available to
read. See the Read Data Continuous section for
more details.
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