ADMV4530 SPI MISO held high

Hi Experts:

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!

  • 0
    •  Analog Employees 
    on Jul 20, 2021 8:43 PM

    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 [3] 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 [6] to value 0 for reading PLL registers, and value 1 for reading mixer registers.