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What's the operation frequency of PIC without crystal?

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alzomor

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Hi,

In some Proteus examples I found circuits based on PIC micro but they don't use any crystal or RC Circuit.
Is it possible to use PIC without crystal?
I wounder if it's used as an RC circuit with R=infinity but I didn't find information in the data sheets of pic about this point.
I have another question, What's the frequency of operation in these cases where there's no crystal is connected.

Salam
Hossam Alzomor
 

PIC without crystal

That’s because they have on-chip RC oscillator thus you don’t need external oscillator if frequency range provided by internal oscillator is suitable for your application.
 

    A

    alzomor

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Re: PIC without crystal

ATtiny2313 has also build in osc circuit
 

Re: PIC without crystal

What about the frequency of this on hip RC oscilator?
 

Re: PIC without crystal

Some PIC models have the internal RC oscillator but the frequency and accuracy are variable depending on the model.

As for example: 16F628 has 2 frequencies: 4MHz and 37kHz (5% precision not adjustable)
16F88 works with 8, 4, 2, 1 MHz, 500, 250, 125 and 31 kHz (adjustable).
 

Re: PIC without crystal

alzomor said:
What about the frequency of this on hip RC oscilator?
Click to expand...

It might change from device to device so please refer to datasheets.
 

PIC without crystal

hi my friend.

proteus didn't simulate oscillators for MCUs and crystal is only a schematic.

for more info see its help

regards
Mostafa, Iran
 

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    alzomor

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Re: PIC without crystal

Where external oscillator circuitry is present on an ISIS schematic it is there purely for aesthetic reasons and is excluded from simulation (by adding the property PRIMITIVE=NULL in the edit component dialogue form).

Processor clock frequency is specified as a property of the microcontroller (edit the component and type in the clock frequency). It would *seriously* affect simulation performance (a 20Mhz analog oscillation takes a whack of computation for example) for no benefit.

This is undoubtedly the most common reason for slow simulation performance.

Iain.
 

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    alzomor

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Re: PIC without crystal

CHECK THIS PIC DATASHEET .........16C685......IT CONTAINS ALL THE INFORMATION.......
 

Re: PIC without crystal

CPU without Clock generator should not be CPU.
 

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