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Regarding 1152 kbps baud rate using 89C52

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mtahirq

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115200 baud to kbps

Hello ....

I am interfacing micro-controller 89C52 with mobile phone. I need to communicate it at 115.2 kbps (only working baud rate for Nokia 3310 ). I want to know that How can i get 115.2 kbps using 11.0592 MHz crystal ???

if not then Can I use 22.11 MHz crystal with 89C52 ? :cry:

Many Thanks

Tahir
 

115200 baud rate using 11.0592

You have to use 22.1184MHz crystal, that is the only way of getting 115.2kbps out of 89C52 ..

Regards,
IanP
 

    mtahirq

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89s52 maximum baud rate

For IanP:- Thanks a lot for your help ...

Can you please tell me one more thing that :-

Should I use 33pf capacitors with 22.1184MHz crystal as we use with 11.059MHz ?? and i hope the rest of the circuit will be same as with 11.059MHz ....

Thanks

Tahir
 

89c52 baud rate

As the Crystal, 22.1184 MHz, HC49/SU, has Parallel 20pF requirement you may change these caps from 33pF to 22pF, but just try with 33pF and if it works well leave them there ..
The rest of the circuit stays as with 11.0592MHz ..

Regards,
IanP
 

89c52 uart baud rate

Xtal is the minimum requirement for 115.2kHz baud rate.

Let's imagine,
In standard 51 architecture, we need 12 clocks for executing an instruction.
At 22MHz Xtal, instructions are executed at 1.8 MHz.
Roughly, 12.8K bytes are transmitted in a second.
So, your processor must finish all the receive and transmitt job in 141 instructions (1.8MHz / 12.8K).

It would be a tough job.

Added after 5 minutes:

Xtal is the minimum requirement for 115.2kHz baud rate.

Let's imagine,
In standard 51 architecture, we need 12 clocks for executing an instruction.
At 22MHz Xtal, instructions are executed at 1.8 MHz.
Roughly, 12.8K bytes are transmitted in a second.
So, your processor must finish all the receive and transmitt job in 141 instructions (1.8MHz / 12.8K).

It would be a tough job.
 

IanP said:
You have to use 22.1184MHz crystal, that is the only way of getting 115.2kbps out of 89C52 ..

Well, not exactly the only way... use T2 for baudrate generation, if it's a 89C52... or an external UART :-D

wek
 

    mtahirq

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Wek,

no matter which timer you are using the divider is an integer. If you multiply the baudrate with the sample frequency and the divider for the UART block that is how you get to the 22.1184.

There are other 51-devices that have a so called fractional baudrate generator like the Philips LPC900 devices, they can generate 115200 from much lower crystal frequencies or even from an internal RC-oscillator.

T2 can not divide in fractions but you can get the device to run with different frequencies, approaching the 115200 "close enough"

Bob
 

Bob,

mtahirq asked:
> I want to know that How can i get 115.2 kbps using 11.0592 MHz crystal ???

From any 8052 datasheet:
Modes 1 and 3 Baud Rate = Oscillator Frequency/(32 × (65536-[RCAP2H:RCAP2L])
For RCAP2H:RCAP2L=(65536-3) and 11.0592MHz oscillator you get 115200 Baud.

Note that using Timer2 as a baudrate generator yields potentially 6x higher baudrate than the highest baudrate achievable when Timer1 is used as baudrate generator (withc the same Xtal).

Of course what you said about derivatives with separate baudrate generator, that holds 100% true.

wek
 

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