Luigi Rizzo <PICLIST@MITVMA.MIT.EDU> wrote:

> > 5473758:  System having input output pins shifting between
> >           programming mode and normal mode to program memory
> >           without dedicating input output pins for
> >           programming mode
>
> this is weird... EPROM have been out for a while and it seems to me
> that the above description exactly matches the programming method
> for EPROMs! (yes I know Eproms have a Vpp pin, but just call it
> RESET...)

Luigi:

Read the patent before jumping to conclusions.

The patent specifically claims a means by which the chip is
programmed with FEWER PINS than the width of each memory cell... Here
are some selected quotes from the Background and Summary sections of
the patent:

    "It is a principal object of the present invention to provide
    apparatus and method which permits the use of 14-bit instruction
    words despite the presence of only 12 I/O pins in the
    microcontroller.",

    ".... Another object of the invention is to provide a
    semiconductor device which may be programmed while in circuit
    without the need for additional pins relative to those utilized
    for the normal circuit or system operating mode.

    "A further object of the invention is to provide a
    microcontroller device which may be user-programmed while
    embedded in the system which is to undergo control.", and

    "According to another significant aspect of teh invention, the
    microcontroller is provided with a serial-parallel interface
    between the I/O ports and the program memory, to allow both
    serial and parallel programming of the device."

As I said in my original message in this thread, though, Microchip
may have some problems with this particular patent... Two of its ten
claims relate directly to the use of EPROM memory (the SX chip uses
flash of some sort), one of the claims (and portions of two others)
relates to the suppresion of disturbances caused by the high
voltages associated with EPROM programming, a couple others involve
implementation issues (latches between the pins and the memory) that
might be worked around, and there's always the dim possibility that
Scenix might be able to show prior art for the other claims.

This particular patent, though, seems to be the weakest of the six
that Microchip is suing over... Even if the case goes to trial and
this one's invalidated, the others will probably (in my opinion
as a non-lawyer) stand up.

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499