Does pinMode 'input' state place pin in tri-state mode for SPI multi device connectivity?

pinMode 'input' - Digital input: Is the pin in tri-state mode?

Yes - it is just leaving the input floating.

I'm not entirely sure what you're trying to do though? In SPI you have 3 pins:

• CLK - master -> slave
  
• MOSI - master > slave
  
• MISO - slave -> master
  
• And often chip select, which is also master-> slave
  
  

The master never has to change the state of any of its pins, and Espruino can only be an SPI master so I don't think you have a problem.

It's actually not a good idea to leave SPI pins from a master tristate since electrical noise could then potentially send random data to the SPI slave(s).

If it were an SPI slave then yes, as I understand it the device would have to tri-state its MISO pin when the chip select was high (unselected), but I believe that's something that is done in hardware