Hello, finally I tested the IP module, automatically the XPS inserts the required buffers. The point is to use the signals named Sda and Scl. These signals should be connected to external ports. Below is a fragment of the MHS and UCF files.
UCF
-----------------
# I2C
NET xps_i2c_Sda_pin LOC=A6 | IOSTANDARD=LVCMOS33 | SLEW=SLOW | DRIVE=4 | PULLUP; # IO5
NET xps_i2c_Scl_pin LOC=B6 | IOSTANDARD=LVCMOS33 | SLEW=SLOW | DRIVE=4 | PULLUP; # IO6
------------------------
In this case I use PULLUP because there aren't external pull ups.
MHS
------------------
PORT ....
PORT xps_i2c_Sda_pin = xps_i2c_Sda, DIR = IO
PORT xps_i2c_Scl_pin = xps_i2c_Scl, DIR = IO
PORT ...
....
BEGIN xps_iic
PARAMETER INSTANCE = xps_i2c
PARAMETER HW_VER = 2.03.a
PARAMETER C_BASEADDR = 0xC0000000
PARAMETER C_HIGHADDR = 0xC000ffff
BUS_INTERFACE SPLB = mb_plb
PORT Sda = xps_i2c_Sda
PORT Scl = xps_i2c_Scl
END
Using this example I can work with I2C peripheral.
Thanks to all the people who also replied this thread. Yosmany325.