You wrote;-
>Hello, PICmaniacs

>        I'm using a PIC16f84 at 4mhz, and would like to know if is
>possible to me to create a frequency of 2mhz at some output pin!

>        Maw.

No the instruction clock is at 1mhz and you need to do a branch which needs
two cycles.

start     BSF   porta,0
           NOP
           NOP
           BCF   porta,0
           GOTO start
Makes a square wave of 6 instruction cycles eg 1mhz / 6 not very useful as it
does nothing else.
If you use a 4060 and feed the osc in pin from one of the outputs the
following output will be 1/2 osc in frequency but you will need to use a
higher frequency crystal.

Steve.....