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ADF7021/7020-1 SPI Connections

Question asked by rwyost on Jun 25, 2012
Latest reply on Jun 25, 2012 by AndyR

We want to create a design that will work for either of the aforementioned chips; they appear at a glance to be quite similar.  We weren’t sure which one we want to go with yet, so we were hoping to be able to interchange them on the board.  On page 46 of the ADF7021 datasheet, in Figure 60, a diagram is shown depicting how to connect the chip in SPI mode to a Microcontroller. This is what we want to do however; the diagram is a bit perplexing.  The MOSI (Master Out) pin is shown as an input from the bidirectional data pin on the ADF7021, and the MISO pin (Master In) is shown as an Output to the data clock pin on the ADF7021.  Additionally, in Figure 58, the MISO and MOSI pins are shown to be connected together to the single bidirectional pin “TxRxDATA”, with a series diode on the MISO pin.  This does not make any sense to me however; if the MISO pin is supposed to be the MOSI pin, this would make sense.


My questions:


  • Is there a typo in these figures, whereas the MISO and MOSI pins are interchanged? 
  • If we want to interchange the ADF7021 with the ADF7020-1, can we utilize the same SPI communication scheme with both chips?