RE: [SI-LIST] : Advice for long bus?

Kowal, Keith (kowal@cabletron.com)
Wed, 28 Apr 1999 14:18:48 -0400

chris,
8" etch is a good number to shoot for with the 33mhz with 5 device loads
/ I found the Flash to have
no drive capacity at all , I would have liked to buffer the flash part but
it worked anyway . I think there
may be trouble with 66mhz bus with heavy loading. I used 3 volt logic
also...so if you can afford some delay use some bi-directional parts to
off-set the heavily loaded bus. ABT573, etc...it will clean up the bus.
the other thing is
is ALE or (eq.) this must also buffered (along with other control
signals).... so be
very carefull in layout to observed min/max and hold time requirements of
all your
bus parts.

keith kowal

> -----Original Message-----
> From: Chris Bobek [SMTP:cbobek@cadence.com]
> Sent: Wednesday, April 28, 1999 12:57 PM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : Advice for long bus?
>
> We are designing a board that has a micro with a 32 bit address/data bus
> which will ultimately go to 14 loads (memory, flash, various other
> devices).
> The bus speed hasn't been decided yet, but it will be either 33 or 66MHz.
> Most everything is 3V logic.
>
> Question: Would it be advantageous to use an alternative signaling scheme
> (such as GTL) instead of the LVTTL? There will probably be buffer/drivers
> anyhow since the micro won't be able to drive 14 loads.
>
> Does anybody have any other suggestions/advice? I realize you may need
> more
> info for this, but I want to keep this brief/high-level.
>
> Thank you,
>
> Chris
>
>
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