Funny, i have just read the chapter 4.2.1 dedicated to ANSEL. it is witten that if left set, the bits will lead to a 0 being read everytime.
rc6 and rc7 wew still analog, as you pointed out mister_e. No wonder why i got 0 when reading back.
This is because i'm used to pic16f684 where there is only ansel and no anselh so i didn't think of checking again all registers for 16f690, now I know i should.

in the meantime i wonder if there are other registers that i should care of like these related to serial connections: eusart, ssp,...

We have to think of so many things when using a pic. there are habits and good practices i don't have yet...