Datasheet

SYNC
DIN
DOUT1
SYNC
SCLK
FSYNC
SCLK
ADS1178
SYNC
DIN
CLK
CLK
FSYNC
DOUT1
SCLK
ADS1178
SYNC
DOUT1
SCLK
ADS1178
SYNC
DIN
FSYNC
DOUT1
SCLK
ADS1178
CLK CLK CLK
FSYNC
DIN
FSYNC
Serial
Data
from
Devices
1and2
Serial
Data
from
Devices
3and4
U4 U3 U2 U1
ADS1174
ADS1178
SBAS373B – OCTOBER 2007 – REVISED SEPTEMBER 2008 ........................................................................................................................................ www.ti.com
To increase the number of data channels possible in Whether the interface protocol is SPI or Frame-Sync,
a chain, a segmented DOUT scheme may be used, it is recommended to synchronize all devices by tying
producing two data streams. Figure 23 illustrates four the SYNC inputs together. When synchronized in SPI
ADS1178s, with a pair of ADS1178s daisy-chained protocol, it is only necessary to monitor the DRDY
together. The channel data of each daisy-chained output of one ADS1178.
pair are shifted out in parallel and are received by the
In Frame-Sync interface protocol, the data from all
processor through independent data channels.
devices are ready on the rising edge of FSYNC.
Since DOUT1 and DIN are both shifted on the falling
edge of SCLK, the propagation delay on DOUT1
creates a setup time for DIN. Minimize the skew in
SCLK to avoid timing violations.
Figure 23. Segmented DOUT Daisy-Chain, Frame-Sync Protocol (FORMAT[2:0] = 011 or 100)
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