Lee esto que viene en el manual., Esto está cogido del manual actual que es la versión 3.0. Deberías consultar el manual que viene con tu compilador para ver si es lo mismo.,
CRYSTAL Frequency Declare
DECLARE XTAL 4 , 8 , 10 , 12 , 16 , 20, or 24. For 12-bit core devices.
DECLARE XTAL 3 , 4 , 8 , 10 , 12 , 14 , 16 , 20, or 24. For 14-bit core devices.
DECLARE XTAL 3 , 4 , 8 , 10 , 12 , 14 , 16 , 20 , 24 , 25 ,32 , 33 , or 40. For 16-bit core devices.
Inform the compiler as to what frequency crystal is being used. Some commands are very dependant on the oscillator frequency, RSIn, RSOut, DelayMS, and DelayUS being just a few. In order for the compiler to adjust the correct timing for these commands, it must know what frequency crystal is being used. If an XTAL frequency of 3 or 14 is chosen, then the resulting code is produced for 3.58MHz and 14.32MHz respectively. If the DECLARE is not used in the program, then the default frequency is 4MHz.
Saludos,
Ricky