In our RF LNB, three LMX2594 RF synthesizers are connected to the Microcontroller SPI Bus. All three LMX2594 chips share the SPI CLK, MISO and MOSI lines (called SCK, MUXout and SDI in the datasheet). Each LMX2594 device has its Chip Select signal from the microcontroller (CSB). We can read and write if there is only one device populated. If we populate all three devices, we can’t read the registers from any of them. We know programming each by looking at the RFoutput is doable. When probing with the oscilloscope, there are good-quality SPI CLK and SPI MOSI signals but no MISO signal. What is the reason of corrupted MISO signal?