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[SOLVED] Controller with Different operating frequencies

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achar.deepak

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Hi everyone,

My name is Deepak. I have one doubt regarding the subject I mentioned. Suppose I have 8051 microcontroller with LCD display and LPC2148 with another LCD display. Both are operating at different frequencies as we know. Is it possible to communicate two controllers through any serial communication protocol like UART, I2C or CAN? If it is possible, how. Please clarify my doubt.

Regards
Deepak, India
 

Interfaces has their own frequencies not related anyhow to core frequency. For all that you mentioned core frequency doesn't mean anything. You need to learn more about interfaces, Deepak.
 

Hi,

Both are operating at different frequencies as we know.
We don´t know this.
You may run both controllers with the same clock frequency.
But what is "same" clock frequency? Driving both controllers with individual 12MHz clocks is just "almost" the same frequency.. it is never exactly the same frequency.

Is it possible to communicate two controllers through any serial communication protocol like UART, I2C or CAN? If it is possible, how. Please clarify my doubt.
I wonder why you ask. For sure this is possible.
Imagine: Over decades of years devices communicate with UART. Maybe a PC with a printer. The PC may run with any frequency but surely the controller inside the printer doesn´t run with the same frequency. And if you connect a printer from one PC to another PC then the printer insider controller will not adjust it´s operating frequency to the PC´s operating frequency.

UART: is an asynchronous interface. Both interfaces need to run with the same baud rate setup (not controller system clock). There are standardized baud rates and each device´s baud rate may have a tolerance of some percent +/- referenced to the "ideal baud rate".

I2C: is a synchronous interface. There is an extra clock line. There is a very wide range of acceptable I2C clock frequency. There are different "speed grades" which just specifies the upper clock frequency limit. If both partners are pecified for a speed grade of 400kHz you are allowed to transmit at 50kHz... and the communication partner doesn´t need to know this. No setup necessary.

Klaus
 

UART uses baudrate. If baudrate of both devices are same then there is no problem in communicating. Same applies for I2C with same I2C clock speeds. MCU clock frequency has nothing to do with peripheral communication.
 

Hi,

Same applies for I2C with same I2C clock speeds.
No.
* With UART both partners need the same baudrate setup.
* With I2C there is no need for same speed setup.

Klaus
 

Hi,

I got my doubt cleared.

Thanks to all.
 

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