PIC internal vs external mhz

[liamfoxtrot@gmail.com]

If a microchip pic has an internal mhz, does it need an external
crystal? If not, what are the pros and cons of doing so?

Thanks,
Andy

PS I am looking at working with PIC16F684

 

[Pooh Bear]

"liamfoxtrot@gmail.com" wrote:

If a microchip pic has an internal mhz,

!!!!

does it need an external
crystal? If not, what are the pros and cons of doing so?

You're new at this aren't you ?

It helps if you use the right terms. The data sheet will assist. I don't
know the PIC but I do know some of flavours of the 8051 have an internal
RC oscillator. If you use that, you don't need an external crystal or
clock oscillator. That's the whole point.

RC oscillators aren't very accurate so no good for accurate timing. Nice
and cheap though.

I tend to use resonators rather than crystals. Still quite accurate but
a bit lower cost.

Graham

 

[John Popelish]

liamfoxtrot@gmail.com wrote:

If a microchip pic has an internal mhz, does it need an external
crystal? If not, what are the pros and cons of doing so?

Thanks,
Andy

PS I am looking at working with PIC16F684

Download the data sheet and refer to it any time you wonder about this
chip:
http://ww1.microchip.com/downloads/en/DeviceDoc/41202C.pdf

Section 3 gives you all the clock choices available or usable.
External clock source, 3 different frequency ranges of crystals or
ceramic resonators, External RC fed oscillator, internal RC oscillator.

 

[Rich Webb]

On 22 Jul 2005 18:42:19 -0700, "liamfoxtrot@gmail.com"
<liamfoxtrot@gmail.com> wrote:

If a microchip pic has an internal mhz, does it need an external
crystal? If not, what are the pros and cons of doing so?

Pro: no additional parts required.
Con: a less accurate system clock that's relatively sensitive to
temperature changes as compared to other possible clock choices.

--
Rich Webb Norfolk, VA