memcals

[Shannen Durphey]

It sounds like you placed the file in the wrong half of the chip.  The end of the
file needs to be located in the highest address of the chip.  So a 16k file in a
32k eprom should begin at address 0x4000.

As far as the question "...the addresses 0x4000 - 0x3fff are they the upper half or
the lower half?"  I'll say that I call it the lower half because that's what it's
generally referred to by other listers and because that's the way I learned to
refer to it.  But I don't really know if that's technically correct.  Anyone?

Shannen

Dave wrote:
> 
> -----Original Message-----
> From: Shannen Durphey <shannen at grolen.com>
> To: gmecm at diy-efi.org <gmecm at diy-efi.org>
> Date: Wednesday, May 02, 2001 2:41 AM
> Subject: Re: memcals
> 
> >Yes, that's correct.
> >
> >Is this an image that you've successfully burned into an eprom before?
> 
> Yes, plenty of times.
> 
> >A 16k image should start at 0x4000 in a 27c256 eprom, and should continue
> until the
> >end of the eprom.
> >I used to use a hex editor to copy -n- paste the image to itself to get the
> proper
> >size file.
> 
> This might be a stupid question, but, the addresses 0x4000 - 0x3fff are they
> the upper half or the lower half?
> I put the 16k image in 0x000 - 0x3fff, is that what I did wrong?
> 
> >If you read the file back from the eprom, does it match the original when
> viewed
> >with a hex editor?
> 
> Yes
> 
> >If your original file is directly from a gm eprom, it may already be
> "double
> >stuffed."  GM often uses 27c256's where a only 128 is needed.  In those
> cases, the
> >contents of the lower half is unpredictable.
> >Shannen
> >
> >Dave wrote:
> >>
> >> -----Original Message-----
> >> From: Shannen Durphey <shannen at grolen.com>
> >> To: gmecm at diy-efi.org <gmecm at diy-efi.org>
> >> Date: Tuesday, May 01, 2001 10:10 AM
> >> Subject: Re: memcals
> >>
> >> >Place the image into the upper half of the eprom.
> >> (27C128 ----> 27C256)
> >> I tried that today and the ecm rejected it.  What am I doing wrong?  I
> left
> >> the lower half blank (ff,ff,ff etc..). Is this correct?
> >>
> >> Dave.
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> 
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