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'[OT:] What is a buffer'
2004\01\12@090333 by #LEE CHUN YONG#

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Hi All,
I notice nowadays a lot of devices are having buffer of certain size. What is a buffer actually and what are the purposes of it?

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2004\01\12@100257 by Rick C.

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A buffer is a temporary storage area. It is usually used to store incoming or outgoing data where there are differences in speed in
the sending and receiving application or device. The size of the buffer depends upon the ratio of the two applications speed. You
always want to have enough buffer memory. Obviously, if an app sends too fast, a overrun error and loss of data will occur. More
memory would then be needed or buffer space allocated. Some applications use handshaking to temporarily halt the flow of data until
the receive app processes it. Buffers are used in almost all applications related to computers. You have keyboard buffers, hard
drive buffers, memory buffers, modem buffers, i/o buffers (comm ports), CD burners, etc.

CD burners can have an underrun error. This is because the data being burned has to burn at a certain rate. If the computer doesn't
have the data ready in time, the burner will not keep up and damage the CD will occur. Most later software calculates and caches the
data into a buffer so there will always be data ready until the CD burn is completed.

Rick

#LEE CHUN YONG# wrote:

> Hi All,
>
> I notice nowadays a lot of devices are having buffer of certain size. What is a buffer actually and what are the purposes of it?

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2004\01\12@103443 by #LEE CHUN YONG#

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Hi Rick,
I am still not too sure about the size of the buffer needed. Is it true that if  the receiver's speed is 1byte/sec and transmitter speed's is 4byte/sec then buffer size of 4-byte is needed.
Thank you and have a nice day.
Regards,
Lee

________________________________

From: pic microcontroller discussion list on behalf of Rick C.
Sent: Mon 1/12/2004 11:03 PM
To: spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU
Subject: Re: [OT:] What is a buffer



A buffer is a temporary storage area. It is usually used to store incoming or outgoing data where there are differences in speed in
the sending and receiving application or device. The size of the buffer depends upon the ratio of the two applications speed. You
always want to have enough buffer memory. Obviously, if an app sends too fast, a overrun error and loss of data will occur. More
memory would then be needed or buffer space allocated. Some applications use handshaking to temporarily halt the flow of data until
the receive app processes it. Buffers are used in almost all applications related to computers. You have keyboard buffers, hard
drive buffers, memory buffers, modem buffers, i/o buffers (comm ports), CD burners, etc.

CD burners can have an underrun error. This is because the data being burned has to burn at a certain rate. If the computer doesn't
have the data ready in time, the burner will not keep up and damage the CD will occur. Most later software calculates and caches the
data into a buffer so there will always be data ready until the CD burn is completed.

Rick

#LEE CHUN YONG# wrote:

> Hi All,
>
> I notice nowadays a lot of devices are having buffer of certain size. What is a buffer actually and what are the purposes of it?

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2004\01\12@104143 by Wouter van Ooijen

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> I am still not too sure about the size of the buffer needed.
> Is it true that if  the receiver's speed is 1byte/sec and
> transmitter speed's is 4byte/sec then buffer size of 4-byte is needed.

If that is the case no finite buffer size wil help you. A buffer can
absorb a burst that arrives faster than it can be handled. The size must
be the size of the burst, minus what can already be transmitted during
the burst, plus a safety margin.

Wouter van Ooijen

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Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products

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2004\01\12@114305 by Rick C.

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Since this was directed to the OT tag, I assumed you were talking about
buffers in general. If you are programming and using pic's or other
processors, more information is required to put this into context. Your
processor speed, tasks performed, and what you are interfacing to, if
serially, needs to be divulged in order anyone to comment. However, this is
really a matter of your programming skills and your understanding your task
loops and what the maximum speed of the data is streaming into your
processor.
Rick

Wouter van Ooijen wrote:

{Quote hidden}

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