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Second asynchronous interface on a 80C51- atmel application note


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Nicolas30

Thu Oct 02 2008, 05:01AM

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I am using this Atmel application note:

http://www.atmel.com/dyn/resources/prod_documents/doc3ab877f2ec329.pdf

I would like to work to 9600 bauds, I change the TH1 register value to 0FDH and the SR_SPEED to 4, but this application don´t works with this values.
Somebody can help me?
Thanks.

Now works fine, we should not change the value of the TH1 register, always 0E8H.

But, what are the values for SR_SPEED variable, if we have TH1=0FDH ?

[ Edited Thu Oct 02 2008, 10:04AM ]

Ajay

Thu Oct 02 2008, 02:55PM

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the timer mentioned there is not the same timer you are looking for. As you can see its a software UART, so there should be someone to provide delay for minimum unit(a bit) to be transferred. This delay is kept multiple of what is loaded into timer (0xE8). and delay is maintained using a counter (si_count).

so you should not play with the timer instead you just have to vary si_count variable's value to change your final baud rate.

if you looked in our tutorial section, you will find software uart code in Serial Communication tutorial, which can be used with assembly as well as C programs. I am sure it will be useful for you. Drawback is you can only have half duplex communication.

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Ajay

Thu Oct 02 2008, 02:56PM

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[topic moved to 8051 discussion forum]

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Nicolas30

Fri Oct 03 2008, 12:18AM

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Thank you Ajay, but I need to have two 9600 bauds serial port, for this reason I need to load the register TH1 with 0FDH value, in this situation I dont know which is the si_count variable to make the second serial port works properly to 9600 bauds.
Many thanks

Ajay

Fri Oct 03 2008, 12:39PM

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I think atmel has not given much information in their application note.

But what i felt from application note i explained. code is bit confusing, but still ok if it works.

If you want you can try code in tutorial too.

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Nicolas30

ExperimenterUK

Fri Oct 03 2008, 04:54PM

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Nicolas30 wrote ...

@Nicolas30

As I understand the method,
for hardware and software ports to be the same set si_count to 32
as they do in the pdf.

Just don't ask me why

[ Edited Fri Oct 03 2008, 04:58PM ]

Learning all the time

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Nicolas30

Nicolas30

Mon Oct 06 2008, 03:52AM

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I tested the web tutorial code and works fine,
in the transmission there is no problem
but the problem is in the reception to synchronize the data input, we can do that by pooling or through an external interrupt.
Thx