Datasheet

DIN
SCLK
DRDY
Status
SLEEP
NormalMode SleepMode
FinishCurrentConversion
NormalMode
StartNewConversion
EighthSCLK
WAKEUP
0000001X 0000000X
Synchronization
OccursHere
2t
OSC
SYNC
DIN
SCLK
0000010X 0000010X
SCLK
RESET
1 8
AnySPI
Command
DIN
0.6ms
ADS1246
ADS1247
ADS1248
SBAS426G –AUGUST 2008–REVISED OCTOBER 2011 www.ti.com
SYSTEM CONTROL COMMANDS
WAKEUP—Wake up from sleep mode that is set by the SLEEP command.
Use this command to awaken the device from sleep mode. After execution of the WAKEUP command, the
device wakes up on the rising edge of the eighth SCLK.
SLEEP—Set the device to sleep mode; can only be awakened by the WAKEUP command.
This command places the part into a sleep (power-saving) mode. When the SLEEP command is issued, the
device completes the current conversion and then goes into sleep mode. Note that this command does not
automatically power-down the internal voltage reference; see the VREFCON bits in the MUX1 register for
each device for further details.
To exit sleep mode, issue the WAKEUP command. Single conversions can be performed by issuing a
WAKEUP command followed by a SLEEP command.
Both WAKEUP and SLEEP are the software command equivalents of using the START pin to control the device.
Figure 73. SLEEP and WAKEUP Commands Operation
SYNC—Synchronize DRDY.
This command resets the ADC digital filter and starts a new conversion. The DRDY pin from multiple devices
connected to the same SPI bus can be synchronized by issuing a SYNC command to all of devices
simultaneously.
Figure 74. SYNC Command Operation
RESET—Reset the device to power-up state.
This command restores the registers to the respective power-up values. This command also resets the digital
filter. RESET is the command equivalent of using the RESET pin to reset the device. However, the RESET
command does not reset the SPI interface. If the RESET command is issued when the SPI interface is in the
wrong state, the device does not reset. The CS pin can be used to reset SPI interface first, and then a
RESET command can be issued to reset the device. The RESET command holds the registers and the
decimation filter in a reset state for 0.6ms when the system clock frequency is 4.096MHz, similar to the
hardware reset. Therefore, SPI communication can be only be started 0.6ms after the RESET command is
issued, as shown in Figure 75.
Figure 75. SPI Communication After an SPI Reset
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