I'm reading tutorials about PIC16F628A, I found that in all project they use a Crystal Oscillator, is it means that the PIC doesn't any internal clock and it cant run without an external Crystal Oscillator??

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    \$\begingroup\$ The datasheet is the first thing that you should check. This particular device in fact has two internal oscillators. Look up. \$\endgroup\$
    – Sohail
    Jun 7, 2014 at 10:59
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    \$\begingroup\$ -1 since the answer is in the datasheet right where you'd expect to find it. Duh! \$\endgroup\$ Jun 7, 2014 at 12:04
  • \$\begingroup\$ sorry my quesiton cannot be deleted, what's this -3 I will leave this site :/ \$\endgroup\$
    – makouda
    Jun 7, 2014 at 12:24
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    \$\begingroup\$ haha! "I will leave this site" with your tail between your legs I assume. It's all good man, gotta learn somehow. Just take their advice - always read the datasheet to avoid silly questions like this one \$\endgroup\$
    – KyranF
    Jun 7, 2014 at 13:37
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    \$\begingroup\$ hhhhhhh ok sorry, I will never do this again, datasheet first and google after. than I can ask valuable question :) \$\endgroup\$
    – makouda
    Jun 7, 2014 at 13:55

2 Answers 2


It's on page 3 of the data sheet

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Internal and external oscillator options:
- Precision internal 4 MHz oscillator factory calibrated to ±1%
- Low-power internal 48 kHz oscillator
- External Oscillator support for crystals and resonators
source (3rd page) - http://ww1.microchip.com/downloads/en/DeviceDoc/40044F.pdf

All (or almost all) microcontrollers have internal clocks. Reasons for using external oscillators vary, but usually because they are more accurate and have higher selection of frequencies than internal RC oscillators. They are also cheap and do not take much place.

Before reading tutorials, you should become familiar at least with microcontroller capabilities by reading datasheets.


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