Register programming information on the SDIO pin is clocked into a shift register on each rising edge of the SCK signal. On the rising edge of the CS* signal, the register is sent from the shift register to the register addressed. A slew rate of at least 30 V/µs is recommended for these signals. After programming is complete the CS* signal should be returned to a high state. If the SCK or SDIO lines are toggled while the VCO is in lock, as is sometimes the case when these lines are shared with other parts, the phase noise may be degraded during this programming.

4-wire mode read back has same timing as SDIO pin.

R/W bit = 0 is for SPI write. R/W bit = 1 is for SPI read.