SBASAM0B March 2024 – November 2024 ADS127L18
PRODMIX
The SPI supports daisy-chaining to connect multiple devices. For daisy-chain operation, connect the SDO pins to the SDI pins of the following devices. There is no special programming required, simply apply additional shift clocks to extend the frame length to access all devices in the chain. To input data, first shift in the data intended for the last device in the chain. The devices interpret the last two or three bytes of data prior to taking CS high (three bytes if CRC is enabled). Data is shifted out from the last device in the chain followed by data from the first device in the chain.
Figure 7-50 shows a two-device, daisy-chain connection and Figure 7-51 shows the data format for a register write commands for each device. The Data Out line of the controller connects to ADC (1) SDI and ADC (2) SDO connects to the Data In line of the controller. ADC (1) input data is shifted out on SDO to drive the ADC (2) SDI. 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 in to each device are interpreted. The second frame shifts out the register data from both devices through the ADC (2) SDO pin.