Re: [SI-LIST] : Terminating a bidirectional bus

Shayle Hirschman (shayle@mho.net)
Mon, 03 May 1999 15:39:03 -0500

Thanks for letting me know, Arrigo.

I tend to agree with Michael Fox on using parallel termination at both
ends. That has always worked well for me.

Does anyone have any opinions on whether 3.3 v devices have less voltage
swing and, therefore maybe, don't need termination as much as 5 volt
devices? Or do they still swing to the rails and so the same principals
apply as with 5 v?

At 12:49 PM 5/3/99 -0700, you wrote:
>Shayle Hirschman <shayle@mho.net> writes:
>
>> May I add to your question what would the answer be if the FPGA and RAM are
>> 3.3 v devices vs. 5 v devices? Would less of a voltage swing reduce the
>> need for termination, especially, as you are asking, on the data lines?
>>
>> Shayle
>
>These are 3.3V devices and from some simulations that one of our students is
>doing with Hyperlynx we see that even a 3'' inch trace needs a series
>termination to get a clean waveform at the receiver's end. We are using IBIS
>models for the Xilinx Virtex FPGA and a Micron ZBT SRAM device.
>
>-Arrigo
>--
>Dr. Arrigo Benedetti o e-mail: arrigo@vision.caltech.edu
>Caltech, MS 136-93 < > phone: (626) 395-3695
>Pasadena, CA 91125 / \ fax: (626) 795-8649
>
>>
>>
>> At 09:21 AM 5/3/99 -0700, you wrote:
>> >Dear all,
>> >
>> >I would like to know you opinion on this issue. I am interfacing a
>> >state of the art FPGA with a high speed synchronous SRAM device. Since
>> >the interface is bidirectional (the FPGA will read and write data to
>> >the memory) I was wondering what is is the best way to terminate this
>> >bus. My intuition is that if the data lines are not very long, then a
>> >series termination near the FPGA end could have an effect similar to a
>> >series termination near the memory end when the memory is driving the
>> >bus.
>> >
>> >I've in the the standard SI book, and haven't found any hint on the
>> >problem.
>> >
>> >thanks in advance
>> >
>> >-Arrigo Benedetti
>> >--
>> >Dr. Arrigo Benedetti e-mail: arrigo@vision.caltech.edu
>> >Caltech, MS 136-93 phone: (626) 395-3695
>> >Pasadena, CA 91125 fax: (626) 795-8649
>> >
>> >**** To unsubscribe from si-list: send e-mail to
>> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
>> si-list, for more help, put HELP. si-list archives are accessible at
>> http://www.qsl.net/wb6tpu/si-list ****
>> >
>> >
>>
>> **** To unsubscribe from si-list: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list, for more help, put HELP. si-list archives are accessible at
http://www.qsl.net/wb6tpu/si-list ****
>
>**** To unsubscribe from si-list: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list, for more help, put HELP. si-list archives are accessible at
http://www.qsl.net/wb6tpu/si-list ****
>
>

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****