Figure 6-15 illustrates an SPI waveform for reading registers in daisy-chain configuration.
Steps for reading registers from N ADCs connected in daisy-chain are:
- Register read is enabled by
writing to the following registers:
- Write to REG_BANK_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 by:
- N × 24-bit SPI frame
containing the 8-bit register address to be read: N times (0xFE,
0x00, 8-bit register address)
- N × 24-bit SPI frame
to read out register data: N times (0xFF, 0xFF, 0xFF)
The 0xFE in step 2a configures the ADC for register read 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.