hi danis,
"Main problem is fast software slave i2c ......"
Remember that while in slave mode, the speed of the S/W will not matter as it has to sample at the edges....
Thus a slave with edge ISR ( Ex: RB0 or RB4-Rb7 for PIC) will be a nice way to write the S/W.
And when using the MSSP in PIC, the speed is not configured as that byte is taken by the slave address register....
I have done a PIC to PIC communication with the peripheral and i had no problems with speed( but i think it is also easy with the ISR of the ports.)
And remember I2C is recomended when u r switching the bus bet'n 2 masters..
Ex: when u want a common EEROM(24c64 etc...) and u want a communication link bet'n all the three..
I did a project some time ago .A 8051 and a PIC would comunicate through a SOFT I2C /. The pic would handle ADC conversions and pass them to the 51 . also The PIC will be like a WATCHDOG for the 51. If the 51 would fail to reset the connection .The PIC would shut evrything down .Let me know if you need the code .. The pic part is in Assembler ..
The 51 is in C .. .
Poonam, you can find numerous application notes on I2C on internet. It's a two wire interface to connect two devices. You can find about I2C in datasheets of microcontrollers also which supports I2C. Even older posts of this forum will be useful to you. First understand the I2C protocol then go for the code. This link might be useful to you.