Post by thread:[EE] max speed of a SPI

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? --------------------------------- Do you Yahoo!? Everyone is raving about the all-new Yahoo! Mail.

> 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.

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_OUTplugwashTakeThisOuTp10link.net> wrote: {Quote hidden}> > > 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. > > -

On 10/18/06, Richard Prosser <.....rhprosserKILLspam@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.

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 {Quote hidden}> On 19/10/06, peter green <plugwashKILLspamp10link.net> wrote: > >>> 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. >> >> --

> 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.

> > > 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.

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 <.....dvanhornKILLspam.....microbrix.com> wrote: {Quote hidden}> > > > > > > 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. > -