I went looking for the "original" SPI specification from Motorola a couple 
of years ago. I ended up talking to an engineer at Motorola who was 
supposedly the "expert" on such documents and she said that there was no 
such document (or spec, for that matter). She said that SPI was originally 
not intended for public consumption; it was for some type of internal 
project and it just grow from that.

In my search I did, however, find a number of articles and designs using SPI 
that put a pull-up on the MOSI (master out/slave in or SDO, as it appears on 
the PIC).

Douglas Wood

----- Original Message ----- 
From: "Andrew Warren" <fastfwd@ix.netcom.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, April 27, 2005 3:42 PM
Subject: Re: [PIC]: Pullups needed on an SPI circuit?


> Olin Lathrop <piclist@mit.edu> wrote:
>
>> I know Phillips owns IIC, but is a license required for SPI?  I don't
>> remember any such restriction, but I could easily be wrong about that.
>
> Olin:
>
> There's no license required for SPI.  In fact, there isn't even a
> real spec for it; in the design documents I wrote for Cypress's
> microcontrollers, I was forced by the lack of an official Standard to
> require "SPI as described in Motorola Semiconductor's M68HC11
> Reference Manual".
>
> -Andrew
>
> === Andrew Warren - fastfwd@ix.netcom.com
>
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