> To clarify, you'd have to switch the SDO output of the
> PIC to high-Z (make it an input) and back during
> transmission/reception to/from this chip in order to
> avoid using the extra control pin.

So the device (with the common SDI/SDO line) must be
accessed "half duplex", as opposed to SPI, which clocks
data in/out on the same pulse?  Is this really SPI then?

> Minimalist solution is a resistor from SDI to SDO on the
> MCU. Value would depend on worst-case bus timing and
> capacitive loading, but something like 4.7K..

What does the resistor do in this case exactly?  Does it
prevent a short-circuit in case both the PIC and device
accidentally drive the line at the same time?

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