Datasheet

START
DRDY
CS
SCLK
DIN
DOUT
ADS1298
(Device1)
START
DRDY
CS
SCLK
DIN
DOUT
ADS1294
(Device2)
START
(1)
a)CascadedConfiguration
CLK
CLK
INT
GPO0
GPO1
SCLK
MOSI
HostProcessor
MISO
CLK
START
DRDY
CS
SCLK
DIN
DOUT
1
ADS1298
(Device1)
START
DRDY
CS
SCLK
DIN
DAISY_IN
2
ADS1294
(Device2)
START
(1)
b)Daisy-ChainConfiguration
CLK
CLK
INT
GPO
SCLK
MOSI
HostProcessor
MISO
CLK
0
DOUT
2
DAISY_IN
1
DOUT
DAISY_IN
1
0
DO TU
0
SCLK
MSB
1
MSB
0
21
3 216
217
218
MSB
1
LSB
0
LSB
1
219
338
LSB
1
Daaft romfirstd ce(evi ADS1298) Daaft romsecond vide ce(ADS1294)
XX
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I –JANUARY 2010–REVISED JANUARY 2012 www.ti.com
Cascaded Mode
Figure 45a shows a configuration with two devices cascaded together. One of the devices is an ADS1298 (eight
channels) and the other is an ADS1294 (four channels). Together, they create a system with 12 channels.
DOUT, SCLK, and DIN are shared. Each device has its own chip select. When a device is not selected by the
corresponding CS being driven to logic 1, the DOUT of this device is high-impedance. This structure allows the
other device to take control of the DOUT bus. This configuration method is suitable for the majority of
applications.
Daisy-Chain Mode
Daisy-chain mode is enabled by setting the DAISY_EN bit in the CONFIG1 register. Figure 45b shows the
daisy-chain configuration. In this mode SCLK, DIN, and CS are shared across multiple devices. The DOUT of
one device is hooked up to the DAISY_IN of the other device, thereby creating a chain. One extra SCLK must be
issued between each data set. Also, when using daisy-chain mode, the multiple readback feature is not
available. Short the DAISY_IN pin to digital ground if not used. Figure 2 describes the required timing for the
ADS1298 shown in Figure 46. Data from the ADS1298 appear first on DOUT, followed by a don’t care bit, and
finally by the status and data words from the ADS1294.
(1) To reduce pin count, set the START pin low and use the START serial command to synchronize and start conversions.
Figure 45. Multiple Device Configurations
Figure 46. Daisy-Chain Timing for Figure 45b
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R