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'[EE] max speed of a SPI'
2006\10\18@114923 by alan smith

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Doing some 'googlin....the best reference I can find is that it can range in the 10's of mhz for a bus speed.  Is there a limitation, other than the clock speeds of the two devices that are talking to each other?  I2C calls out specifics of 100khz, 400KHz and 1.25Mhz, but SPI doesn't seem to have a specific data rate.  Anyone know?
               
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2006\10\18@121331 by peter green

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> Doing some 'googlin....the best reference I can find is that it
> can range in the 10's of mhz for a bus speed.  Is there a
> limitation, other than the clock speeds of the two devices that
> are talking to each other?  I2C calls out specifics of 100khz,
> 400KHz and 1.25Mhz, but SPI doesn't seem to have a specific data
> rate.  Anyone know?

SPI is a very loose standard, you have to read the data sheets (and in some
cases the silicon errata, e.g. early versions of the ENC28j60 are only
reliable with clocks between 8 and 10 mhz unless the ENC and the controlling
processor are on the same clock) for the parts you are using for specifics.

2006\10\18@143939 by Richard Prosser

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Alan,
SPI speed is limited only by the devices connected. I don't think
there are standard speeds - I haven't even heard of an SPI standard as
such.

RP

On 19/10/06, peter green <spam_OUTplugwashTakeThisOuTspamp10link.net> wrote:
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> -

2006\10\18@150021 by David VanHorn

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On 10/18/06, Richard Prosser <.....rhprosserKILLspamspam@spam@gmail.com> wrote:
>
> Alan,
> SPI speed is limited only by the devices connected. I don't think
> there are standard speeds - I haven't even heard of an SPI standard as
> such.


Same here, I've used 8 MHz a lot, but that was limited by the sending
device.

2006\10\18@151803 by Bob Axtell

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Richard Prosser wrote:
> Alan,
> SPI speed is limited only by the devices connected. I don't think
> there are standard speeds - I haven't even heard of an SPI standard as
> such.
>
> RP
>  
If you look at typical MAX speeds, they indicate 2Mhz. RAMTRON has 2Mhz SPI.
But there is no standard like I2C has (max of 100Khz or 400Khz).

--Bob


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>> --

2006\10\18@154440 by peter green

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> If you look at typical MAX speeds, they indicate 2Mhz. RAMTRON
> has 2Mhz SPI.
is that a typo,
www.ramtron.com/doc/Products/Nonvolatile/Nonvolatile_list.asp?ID=5
indicates that thier SPI chips range in max frequency from 5mhz all the way
up to 25mhz.

btw since this is the piclist i belive the maximum SPI speed a PIC18 can
achive is fosc/2, so assuming you are running the chips in spec that means a
limit of 10mhz for most pic18 chips and 12mhz for the USB ones.


2006\10\18@163429 by David VanHorn

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>
>
> btw since this is the piclist i belive the maximum SPI speed a PIC18 can
> achive is fosc/2, so assuming you are running the chips in spec that means
> a
> limit of 10mhz for most pic18 chips and 12mhz for the USB ones.


Fosc on the AVRs.

2006\10\18@235022 by Shawn Wilton

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I know from personal experience that with the right layout you can go above
and beyond 40-50 Mhz with SPI.  But obviously you need to be really careful
at those speeds because of t-line effects and EMI issues.



On 10/18/06, David VanHorn <.....dvanhornKILLspamspam.....microbrix.com> wrote:
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