I'm using a FXLS8471Q accelerometer for a project using the SPI interface. The chip uses the same pins for SPI and I2C. To detect which interface the user desires, the chip samples the SA0 pin on power up according to Table 11:
I have two questions.
To make the SA0 pin appear floating, I connected it directly to the input of a CMOS buffer. The buffer I chose happens to be of the 74LVC series. Since the input to a CMOS device is basically connected directly to the gates of MOSFETs, am I correct in assuming that a CMOS input will "look like" a floating pin to this chip?
What is the internal circuit that the manufacturer likely used to detect a floating pin? One thought that comes to mind is a simple 50/50 resistor divider between power and ground. Sampling the middle of the divider with an ADC or two comparators could tell the difference if the pin is tied high, low, or floating. Is it much more complicated than that?