FPGA Central

Hello,
In out project, we have to interface a Compact Flash card with a
Spartan-3 fpga in Ultra-DMA mode. In the CF 3.0 specifications it
states, that most of the lines need series termination resistors. We
were just wondering, if those termination resistors are really needed,
since the CF will be no more than an inch away from the Spartan 3. If
they are indeed needed, we might have a problem determining the
resistors values and doing signal integrity analisys, since we haven't
been able to find an IBIS model for a CF card.

Best regards
George

George Mercury wrote:
> Hello,
> In out project, we have to interface a Compact Flash card with a
> Spartan-3 fpga in Ultra-DMA mode. In the CF 3.0 specifications it
> states, that most of the lines need series termination resistors. We
> were just wondering, if those termination resistors are really
needed,
> since the CF will be no more than an inch away from the Spartan 3. If
> they are indeed needed, we might have a problem determining the
> resistors values and doing signal integrity analisys, since we
haven't
> been able to find an IBIS model for a CF card.
>
> Best regards
> George

I have not designed with CF, but I'd be more concerned about the
Spartan 3's
3.3v tolerance. The oxide of that device breaks down at 4v and
undershoot
allowed is minimal as well, like .5v

>> In out project, we have to interface a Compact Flash card with a
>> Spartan-3 fpga in Ultra-DMA mode. In the CF 3.0 specifications it
>> states, that most of the lines need series termination resistors. We

Are the series termination resistors needed in all modes of CF data
transfer, or only in the faster modes?

>I have not designed with CF, but I'd be more concerned about the
>Spartan 3's
>3.3v tolerance. The oxide of that device breaks down at 4v and

It should be possible to use Vcc = 3.3V for the CF card.

Mika Leinonen wrote:
> Are the series termination resistors needed in all modes of CF data
> transfer, or only in the faster modes?

The specifications only mention line termination with UltraDMA-66 mode,
which is the fastest. But it's not that fast, since It's "only"
66MBytes transfered on 16 Bit wide bus. Data is transfered on bost
edges of strobe signal so the frequency is no greater then about 16MHz.