questions about I2C configuration

hi:

Now,I am using DE2 board , when I configure A/D chip(ADV7181) using the files (I2C_Controller.v,I2C_AV_Config.v),ADV7181 always back "ACK" high level,that means FPGA cannot comminicate with ADV7181,and I am sure ADV7181 is OK.

so, I write a simple I2C confiuration programme ,ADV7181 back "ACK" low level,that says I2C confiruration success,but I donnot understand why using the demo I2C configuration programme is always unsuccessful??

thanks for your relay~!