In daisy chain mode of operation, the SPI transaction from the controller consists of 3 types of segments: Header (16-bit), Address (Nx16-bit) and Data (Nx8-bit). As the TXE8124 receives the same and transmits it to the next device in the chain, it appends a Status (16-bit) to the transaction, while removing the Address segment and replacing the Data segement that corresponds to its position in the chain.

Figure 7-11 shows an example of a daisy chain write for 2 devices in daisy chain. The header byte is transmitted with the chain length (CL) value of 2, followed by the address for DUT2, DUT1 and then the 8-bit data-in for DUT2, DUT1. As the first device shifts the data out, it transmits its status segement, followed by the original header, address for DUT2, data-out from DUT1 and data-in for DUT2. The final device in the chain sends its status, followed by status for DUT1 and finally data-out for DUT2, DUT1.

Figure 7-11 SPI Daisy Chain Write

Figure 7-12 shows an example of a daisy chain read for 2 devices in daisy chain. The header byte is transmitted with the chain length (CL) value of 2, followed by the address for DUT2, DUT1 and then the 8-bit dummy data-in for DUT2, DUT1. As the first device shifts the data out, it transmits its status segement, followed by the original header, address for DUT2, data-out from DUT1 and dummy data-in for DUT2. The final device in the chain sends its status, followed by status for DUT1 and finally data-out for DUT2, DUT1.

Figure 7-12 SPI Daisy Chain Read