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Message
From: kprataparaju@y...
Date: Thu, 17 Jul 2003 06:33:38 -0100
Subject: Re: [oc] Modular FPGA board (PCI)
I am looking for free PCI IP core model for a simple application . I want
to develop an interface for a 16-bit micromputer system(veri old + slow)
for Data/Address(16-bit) and some control logic. It may be
implementable using CPLD/FPGA Altera/Cypress/Any other.
I have Altera'S QUARTUS web Edition ver 2.
Please suggest me.
pratap.
----- Original Message -----
From: "MikeJ" <mikej@f... >
To: <cores@o... >
Date: Tue, 13 Nov 2001 20:40:35 -0000
Subject: Re: [oc] Modular FPGA board (PCI)
>
>
> From: "Richard Herveille" <richard@a... >
> To: <cores@o... >
> Sent: Tuesday, November 13, 2001 4:35 AM
> Subject: Re: [oc] Modular FPGA board (PCI)
>
>
> A few comments on the comments !
>
> >A few comments on this:
>
> >Paul,
> >
> >Just to repeat my concern, 'standard' 33Mhz 32 bit slots in
> PC's use 5V
> >signalling.
> >
> >The pci connector has a keyed section, which must mate up with
> a
> >corresponding slot in the plug in card. This key slot can be in
> one of two
> >positions (actually the connector is just rotated 180) which
> indicate
> >whether the motherboard uses 5v or 3v3 signalling. Many plug
> in pc cards
> >are 'universal' which means they have two slots and can fit in
> any hole -
> >this is possible by powering the ASIC's IO ring with the VIO
> supply on the
> >PCI connector.
> >This is not possible using virtex FPGA's as VCC_IO cannot be
> 5V.
>
> Doesn't matter. As long as the IO's can handle the over-voltage.
> Some FPGAs
> use 3v3 IOrings, but have dedicated IOpads which can handle 5v
> signals.
> This is normally taken care of by terminating diodes in the IOpads.
>
> MIKEJ : agreed - I was attempting to point out that universal cards
> should
> power
> the output drivers from VCC_IO which can only be 3v3 in a bus
> which
> contains
> 3v3 slots or the 3v3 power rail itself. (pci spec 2.2 page 114).
> Therefore a card in a 3v3 slot does not need to be 5v tolerant - in
> theory
> at least.
> Anyone know any different?
> As you say the important point for universal cards is that the
> inputs are
> tolerant upto
> 5v as in the case of virtex 1 and sparten2.
>
> >If you can guarantee the dev board will only go in 3v3 slots
> (and these are
> >still quite rare) then everything will be fine.
>
> Not true. PCI has set a course where eventually 5v devices won't be
> supported anymore, but there's still a long time to go. This means
> even
> though your board is a pure 3v3 design, PCI signals can still reach
> 5v.
> This is caused by other boards in the system (or even the system)
> which use
> 5v output drivers.
>
> MIKEJ : disagree, see above
>
> >I'm not sure you can get away with external buffers around the
> FPGA for
> PCI.
> >as was suggested :
> >1, as the signals are bi-directional you would have terrible
> timing
> problems
> >and two loads per net - which is illegal
>
>
> the rest has been trimmed as we got told off !
>
> Cheers,
> MikeJ
>
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