SBASAM0A March 2024 – June 2024 ADS127L18
ADVANCE INFORMATION
The SPI supports daisy-chain operation using one CS signal for all devices. Daisy-chaining connects the SDO output of one device to the SDI input of another device. This configuration causes the devices to function as a single unit. There is no special programming required for daisy-chain operation. The device interprets the last two or three bytes of input data prior to taking CS high (depending on the presence of the STATUS byte). Therefore, simply apply additional shift clocks to access all devices in the chain. To input data, the SPI controller first shifts in the data intended for the last device in the chain. To output data, the host shifts out the data from the first device in the chain.
Figure 7-48 shows two devices connected in the SPI daisy-chain configuration. The SDI of ADC (1) connects to the host SPI data out, and SDO of ADC (2) connects to the host SPI data input. During the shifting of input data, SDI appears on SDO to drive the SDI of the next device in the chain. The shift operation continues until the last device in the chain is reached. The SPI frame ends when CS is taken high, at which time the data shifted into the devices are interpreted.