Figure 6-14 depicts an SPI waveform for reading registers in daisy-chain. Steps for reading registers
from N ADCs connected in daisy-chain are:
- A register read is enabled by writing
to the following registers using the register write with daisy-chain operation:
- Write to PAGE_SEL to select the
desired register bank
- Enable register reads by writing
SPI_RD_EN = 0b (default on power-up)
- With the register bank selected and
SPI_RD_EN = 0b, the controller reads register data in the following two steps:
- The N × 24-bit SPI frame containing
the 8-bit register address is read: N-times {0xFE, 0x00, 8-bit register
address}
- The N × 24-bit SPI frame to read
out register data is read: N-times {0xFF, 0xFF, 0xFF}
The 0xFE in step 2a configures the ADC for register reads from the specified 8-bit address.
At the end of step 2a, the output shift register in the ADC is loaded with register data.
The ADC returns the 8-bit register address and corresponding 16-bit register data in step
2b.