Oscillatory circuit in 8051

[RAHUL_KUMAR]

hi,

Do 8051 have also two different oscillatory circuit .,one for main clock which drives CPU and another for sub clock which drives peripherals ??

 

[KlausST]

Hi,

this is a typical information to be found in the datasheet.
What does it say?

Klaus

 

[RAHUL_KUMAR]

sir ,in datasheet at89c51 , there is no information given in this direction.

another question related to this that, is it necessary to give external oscillator to DRIVE oscillatory circuit ?

If no ,then what is the internal oscillator frequency (only attaching resonating capacitor)?

i have gone through a discussion forum of Keil where the conclusion point was that there is no need to use external oscillator to Drive the internal oscillator circuit ...

 

[KlausST]

Hi,

this information has to be written in the datasheet.

Please upload the datasheet.

Klaus

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Added:

I recommend to always use first source infromations: Datasheet directly from the chip manufacturer Atmel/Microchip.
This is the most reliable information.

Klaus

 

[RAHUL_KUMAR]

Hi,

this information has to be written in the datasheet.

Please upload the datasheet.

Klaus

- - - Updated - - -

Added:

I recommend to always use first source infromations: Datasheet directly from the chip manufacturer Atmel/Microchip.
This is the most reliable information.

Klaus

yes i prefer to go through chip manufacturer datasheet.

https://ww1.microchip.com/downloads/en/DeviceDoc/doc0265.pdf

 

[KlausST]

Hi,

There it is:

Read page 4 "Oscillator characteristics"
Read page 13 "External Clock Drive Waveforms"

Klaus

Btw: Datasheet says: "Not recommended for new designs. Use AT89S51.")

 

[RAHUL_KUMAR]

sir ,
in page number 13 ,waveforms are related to external oscillator , not for internal oscillator .

my 2nd question was regarding internal oscillator .

//anyway thanks for guiding//

 

[FvM]

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used.

What's unclear with this datasheet description?

If no ,then what is the internal oscillator frequency (only attaching resonating capacitor)?

You may be confused by the datasheet term "on chip oscillator". As clearly explained in the datasheet, the frequency is determined by an external resonator. It's not the kind of internal RC oscillators you find with modern microcontrollers, e.g. PIC.

 

[KlausST]

Hi,

in page number 13 ,waveforms are related to external oscillator , not for internal oscillator .

You are free to use the internal oscillator or an external clock source.
We can not know what solution is good for you. (Eg: Maybe you already have an external clock source.. or you want a frequency where you can´t find a suitable XTAL...)

In post#3 you twice mentioned "external oscillator", thus I´ve given you the section in the datasheet.

*****
All information you need is in the datasheet. Don´t expect the device to have more features than mentioned in the datasheet (like "single external C oscillator")

Klaus

 

[kumarharsh]

Think it in this way. What is Internal Oscillatory circuit? It is an inverting amplifier which is capable of generating square wave oscillatory output, but we need to input something to its inverting input which can be either independent external clock signal or a crystal resonator which will give amplifier's input.
So to get the output from the amplifier we need to give some input. That's all about it...