On Sun, 29 Nov 1998 mkeitz@JUNO.COM wrote:

> On Sun, 29 Nov 1998 18:56:48 +0000 "Peter L. Peres" <plp@ACTCOM.CO.IL>
> writes:
> >On Sat, 28 Nov 1998, Morgan Olsson wrote:
> >
> >> I thougt it was the same (shift register technique)
> >
> >Microwire is (C) [pat] [tm] Motorola, whereas SPI is an acronym that
> >cannot be patented...
>
> "Microwire" is National's TM.  "SPI" is Motorola's name.  Neither seems
> to have has been too actively sueing other manufacturers for re-using
> their names.

Ok, it looks more confused from here (far away) ;). Thank you for putting
it right.

> >The addressing refers to the fact that some SPI part manufacturers
> >choose
> >to address distinct functions in a chip by the number of clock pulses
> >until ~SS is (un)asserted. Motorola is one of these BTW.
>
> Motorola I think first used this feature and named it "BitGrabber" TM.
> The number of pulses is always a multiple of 8 though.  That to me seems
> to be the major difference: SPI devices try to group the data into bytes
> of 8 because the SPI master hardware in Motorola processors always sends
> 8 bits at a time.  Microwire devices are harder to deal with because they
> send various lengths of data.  For example to upgrade from a 93C46 to
> 93C56 EEPROM would require modifying the sending routine to send an
> additional bit of address.

Actually imho Microwire is easier to deal with because you do not have a
table of commands AND lengths, instead you use a table of lengths only. At
least on very small micros.

BTW there is at least one Motorola device that is message-length addressed
(a la Microwire) that I know well: MC145171, and they're not 8 bit
multiples either. So that much for being consequent. I wonder how one can
program a HC?? SPI master to talk to it (I used a PIC ;).

Peter