Connecting I2C Sensor - what is SS/INT?

Hey!

I hope my question fits in here, otherwise maybe some mod could change the forum.

I'm pretty new in electronics, but for my thesis I have to (an want to) learn some new stuff and this forum already helped me a lot!
My project is to log the output of different level-sensors in a waste-water tank. I already mounted some of them, but the last one gets me a little headache:
It's a differential pressure sensor with I2C bus (http://www.produktinfo.conrad.com/datenblaetter/1500000-1599999/001526119-da-01-en-DRUCKSENSOR_ABPMJJT015PGAA5.pdf). The 6 pins are configurated as listed on page 8: GND, Vdd, SS/INT, NC, SDA, SDL.
As I already used I2C sensors nearly everything is clear to me - I guess NC means something like 'not connected' - but I have no idea what to do whith SS/INT. In my research I found SPI - Arduino Reference but I can't link it to my problem, because SPI shows some more pins like MISO, MOSI or SCK, as I have here, and beside the sensor is listed as I2C. Without connecting that shady pin (connecting only all the others) my Arduino Leonardo scans withou finding any I2C device.
I would be very happy if anyone could help me with this!

According to your datasheet:

Output: ratiometric analog; I2C- or SPI-compatible 14-bit digital output
(min. 12-bit sensor resolution)

So, the SS/INT pin would be used in SPI mode.

It also says:

The following associated literature is available at sensing.honeywell.com:
• Product Line Guide
• Product Range Guide
• Product Nomenclature Tree
• Installation Instructions
• Application Information
• Technical Notes:

  • I2C Communications with Honeywell Digital Output
    Pressure Sensors
  • SPI Communications with Honeywell Digital Output
    Pressure Sensors
  • Sleep Mode with

So, I think you need to do some hunting, or contact them directly, and learn how to use that device.