[Diy_efi] Continuing the chip switcher "problem"
WSCowell at aol.com
WSCowell at aol.com
Fri Feb 11 22:53:00 GMT 2005
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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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face=3DArial color=3D#000000 size=3D2>
<DIV>Martin,</DIV>
<DIV> </DIV>
<DIV>I absolutely agree. There isn't a problem if normal good practice=
is=20
followed. I used to be a hardware designer and would never think=20=
of=20
changing addresses without "locking in" those changes to the read cycle.&nbs=
p;=20
The address upper bits (used for bank switching) should always be stabl=
e=20
during a read. If they aren't latched, there's likely to be=20
trouble. And since it is so simple to do, any quad latch will do it, t=
here=20
really seems no reason not to. The chip data sheets are available, I h=
ave=20
to assume - I'm no longer working as an engineer.</DIV>
<DIV>Good luck and best wishes</DIV>
<DIV> </DIV>
<DIV>Will Cowell</DIV>
<DIV> </DIV>
<DIV>>Marcello,<BR>><BR>>As an electrical engineer, I would say tha=
t it=20
would be wise to Latch your<BR>>bank switching bits on the rising e=
dge=20
of the read strobe. This way the<BR>>address will not change during a REA=
D=20
(usually active low). Ugly things will<BR>>happen and you may not meet th=
e=20
setup and hold times for the Flash memory.<BR>>Also if the bank switching=
=20
wires are 'long' you may be coupling in noise to<BR>>the ECM, as well as=20
switch bounce noise.<BR>><BR>>cheers<BR>>Martin<BR><BR>----- Origin=
al=20
Message ----- <BR>From: <mbelloli at speedymotorsports.com><BR>To:=20
<diy_efi at diy-efi.org><BR>Sent: Thursday, February 10, 2005 6:46=20
PM<BR>Subject: [Diy_efi] Continuing the chip switcher problem<BR><BR><BR>>=
;=20
Hello Everyone,<BR>> I had asked the question eariler=
in=20
regards to creating a multiple<BR>> bank chip switcher for an ecm. =20
Everyone basically said I should be<BR>> able to just switch the chip wit=
hout=20
any regard for whether the chip<BR>> is being accessed during the=20
switch. I finally got my pic chip<BR>> controller up and running.&n=
bsp;=20
I'm running at 20mhz, and when I do a<BR>> switch I'm still getting a che=
ck=20
engine light. 2 out of three times.<BR>> Thinking about this,=
I=20
put the same exact bin in each of the banks<BR>> of the chip, and still g=
et=20
the same response. Could it not be that<BR>> I'm switching in the=20
middle of a read, and that is causing this<BR>> problem??? What doe=
s=20
everyone think. If I turn the car off, and do<BR>> the switch no=20
problem. I'm using this on a 1991 acura integra....had<BR>> a 27c25=
6 as=20
the base chip, and I'm using a 29c010 as the replacement.<BR>> I'm=20
controlling the highest two address lines as bank select for a<BR>> total=
of=20
4 banks.<BR>> I'll put the info for chip changer on m=
y=20
website, and add a link to<BR>> it tonight.<BR>><BR>> =20
Any ideas???<BR>><BR>> Thanks,<BR>><BR>>=20
Marcello<BR></DIV></FONT></BODY></HTML>
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