We are trying config through SPI and meet MISO issue. Below photo are the waveform of LSB first W/R Reg #0, but MISO level always high. (Same result with MSB first)
Could you please advise why MISO pin always high?
Thanks in advance!
To enable the communication from the SDO pin be sure to set bits [4:3] and register 0x000; a typical value for this register will be 0x18.
The next step is then to decide whether you want the SDO pin to output a particular MUXOUT signal from the PLL or if you want the pin to be used for data read back. In register 0x020, set bit  to value 0 for data, and value 1 for MUXOUT signal. The MUXOUT signal from the PLL can be determined using bits [7:4], see register map for details.
When the device is set for data read back and is idle (no communication), the pin will float high impedance to a voltage around 2.3V.
Additionally, there is a data read back page select bit, that needs to be set based upon the section of the chip you are reading. In register 0x117, set bit  to value 0 for reading PLL registers, and value 1 for reading mixer registers.