I am connecting AD9859 with PIC16f876A on i2c. AD9859 works on 1.8v to 3.3v. i2c signal is ok according to timming diagrams. all the coltrol signal are according to the application note. the problem i faced is that sometimes its works(i get a Clock on crystal clock output) and sometimes its not. i cant read back the register yet. why AD9859 works some time and some time not. i have filtered all the noises on power.