but when I conect de 75176 then comunication fail, sometimes the micro can´t be reset, I got to turn off the power. I know that the 75176 change the pin RX when I put him on Reciver or Transmiter.

"the micro can´t be reset" explain, that is normally a power on function.

"I know that the 75176 change the pin RX when I put him on Reciver or Transmiter"
That seems to indicate that RE is permanently low i.e. as opposed to the 232 setup you receive what you transmit, is your software ready for that. In most cases you would connect !RE and DE together.

Erik