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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
 

dipal_z

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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.
 

    alzomor

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mobile-it

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Re: PIC without crystal

ATtiny2313 has also build in osc circuit
 

alzomor

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Re: PIC without crystal

What about the frequency of this on hip RC oscilator?
 

rkodaira

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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).
 

dipal_z

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Re: PIC without crystal

alzomor said:
What about the frequency of this on hip RC oscilator?
It might change from device to device so please refer to datasheets.
 

mtkee2003

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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
 

    alzomor

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Iain

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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.
 

    alzomor

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roykyn

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Re: PIC without crystal

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

sci-3d

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Re: PIC without crystal

CPU without Clock generator should not be CPU.
 

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