What kind of communication protocol is this?
My target is to use a microcontroller (STM32F4) to communicate with
  the slave. When I've tried that, the slave couldn't pull down the data
  sign.


It looks like I2C signalling to me - the data line is pulled up using a resistor and this means that if there are data clashes then it's not an output fighting another output but an open-collector output situation.

If you look at the data line you can see that it returns to logic 1 quite slowly compared with the clock signal and this is also another indication of I2C signalling.