[Diy_efi] Continuing the chip switcher "problem"

[mbelloli at speedymotorsports.com]

     I think I'm following what is being said.  Now here is a link to my
web page with all the info on my chip switcher.
          http://home.comcast.net/~hexibot43/ChipEnableLogic.htm
     I was thinking that I should be doing the switching during the time
that no read was occuring.  Now we're saying that I should do it
immediately after a read occurs.  Does that mean when I see the
moment of a read I immediately do my switch?  Whatever immediatley
means.  I'm hoping everyone will look at the waveform I'm seeing on
my Output Enable pin, and see if they can give me any insite.  I'm
very confused by it.  I swear it never gets near ground.  Help me
ObiWan your my only hope....Marcello





> Martin,
>
> I absolutely agree.  There isn't a problem if normal good practice is
> followed.  I used to be a hardware designer and would never think of
> changing
> addresses without "locking in" those changes to the read cycle.   The
> address upper
> bits (used for bank switching) should always be stable  during a read.  If
> they aren't latched, there's likely to be  trouble.  And since it is so
> simple
> to do, any quad latch will do it, there  really seems no reason not to.
> The
> chip data sheets are available, I have  to assume - I'm no longer working
> as an
> engineer.
> Good luck and best wishes
>
> Will Cowell
>
>>Marcello,
>>
>>As an electrical engineer, I would say that it  would  be wise to Latch
>> your
>>bank switching bits on the rising edge  of the read strobe. This way the
>>address will not change during a READ  (usually active low). Ugly things
>> will
>>happen and you may not meet the  setup and hold times for the Flash
>> memory.
>>Also if the bank switching  wires are 'long' you may be coupling in noise
>> to
>>the ECM, as well as  switch bounce noise.
>>
>>cheers
>>Martin
>
> ----- Original  Message -----
> From: <mbelloli at speedymotorsports.com>
> To:  <diy_efi at diy-efi.org>
> Sent: Thursday, February 10, 2005 6:46  PM
> Subject: [Diy_efi] Continuing the chip switcher problem
>
>
>>  Hello Everyone,
>>      I had asked the question eariler in  regards to creating a multiple
>> bank chip switcher for an ecm.   Everyone basically said I should be
>> able to just switch the chip without  any regard for whether the chip
>> is being accessed during the  switch.  I finally got my pic chip
>> controller up and running.   I'm running at 20mhz, and when I do a
>> switch I'm still getting a check  engine light.  2 out of three times.
>>  Thinking about this, I  put the same exact bin in each of the banks
>> of the chip, and still get  the same response.  Could it not be that
>> I'm switching in the  middle of a read, and that is causing this
>> problem???  What does  everyone think.  If I turn the car off, and do
>> the switch no  problem.  I'm using this on a 1991 acura integra....had
>> a 27c256 as  the base chip, and I'm using a 29c010 as the replacement.
>>  I'm  controlling the highest two address lines as bank select for a
>> total of  4 banks.
>>      I'll put the info for chip changer on my  website, and add a link
>> to
>> it tonight.
>>
>>     Any ideas???
>>
>> Thanks,
>>
>>  Marcello
>
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