[En-Nut-Discussion] Ethernut 3 hardware points: RAM on expansion port and SD card

Ulrich Prinz uprinz2 at netscape.net
Sat Aug 29 23:02:10 CEST 2009

Hi Colin!

Sorry, missed your post in the list.

I didn't use extra ram on the extension connector. I think I remember 
something about 5..8ns for the XilinX CPLD. But you better check the 
datasheets. There is a delay for the signal in general, but there are 
also delays for the gates you put inbetween.

I most answered your questions around the glitches on the SD card 
socket, I hope.

Regards, Ulrich

Colin Chaballier wrote:
> Hi Ulrich,
> Thanks for the point. At which speed did you run the address/data buses 
> ? I don't have a clear idea on the latency introduced by the cpld.
> Any more experiences on the use of the expansion port for external RAM ?
> BR,
> Colin
>> ----------------------------------------------------------------------
>> Message: 1
>> Date: Sun, 02 Aug 2009 17:50:03 +0200
>> From: Ulrich Prinz <uprinz2 at netscape.net>
>> Subject: Re: [En-Nut-Discussion] Ethernut 3 hardware points: RAM on
>>   expansion port and SD card
>> To: "Ethernut User Chat (English)" <en-nut-discussion at egnite.de>
>> Message-ID: <4A75B5AB.3080301 at netscape.net>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>> Hi Colin,
>> I had used the external RAM on Ethernut 3.0e and other SAM7 based 
>> Applications without any problem. Just keep an eye on timing and correct 
>> Chipselects.
>> The power-glitch while handling any hotswap device is a problem that can 
>> be worked around by installing a 100nf and a 1uF capacitor as close as 
>> possible to the vcc/gnd of the socket. This is a workaround as the real 
>> solution should be to design in a slot controller. I.e. a chip that does 
>> bus connection/disconnection including power up / power down of the cards.
>> Best regards, Ulrich
>> Colin Chaballier wrote:
>>> Hi,
>>> As part of the integration of the Ethernut3 in a new design, I'm looking 
>>> at the feasibility to add external RAM through the expansion connector.
>>> Do you have any feedback experience on connecting RAM through the 
>>> "configurable address bus" on this board ?
>>> Apart the 16bit address bus limitation, should be there any issues 
>>> working on the address/data buses through the CPLD logic (latency 
>>> control for example) ?
>>> My second point is about the SD Card support. In the Ethernut3 
>>> documentation it is reported that there should be a power line glitch 
>>> problem when inserting SD card of more than 2GB. Is this problem has 
>>> been definitely solved ? Or could we expect later issues when using 
>>> large capacity SD cards ?
>>> Thanks for your answers.
>>> Best regards,
>>> Colin
>>> _______________________________________________
>>> http://lists.egnite.de/mailman/listinfo/en-nut-discussion
>> ------------------------------
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>> End of En-Nut-Discussion Digest, Vol 70, Issue 3
>> ************************************************

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