Also could be not bad to switch from XT to HC mode as well as
applying two 20pF(15..33) capacitors from osc pins to ground,
just for some reason ;)

Finally check if crystal itself is good (try another one)

WBR Dmitry.

Tyson Stephen wrote:
>
> Hi, I have the 16f84 4mhz micro and I goto a 16f84a 20mhz micro so I swapped out the 4mhz ceramic resonator w/caps  with a 20 mhz and nothing happens, if i substitute the 4mhz back in it works fine?... does anyone know why the 20mhz doesn't work? wouldn't work? the exact numbers on the new micro are pic16f84a - 20/p  0048HEJ

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