[SI-LIST] Re: QDR <=> Processor interface
- From: Dagmara Avanindra <dagmara.avanindra@xxxxxxxxx>
- To: igazula@xxxxxxxxxxx
- Date: Wed, 20 Jul 2005 12:44:19 -0700
Indira,=20
when deceiding upon the trace length, it is important to remember not
just the quality of the signal (clean rise time, voltage margin) but
also timing constraints. You need to take into account propogation
delay into your timing margin. Look at the timing spec of the
interface, and perhaps that will make more sense on length constraint.
The shunt resistor is there to kill off reflections, for having
reflections can break a tight timing interface. You can get rid of the
resistors in your simulation, and see the difference. If your
microprocessor has well-controlled output impedance, there may be a
chance that you can get away without the termination resistors. But
you need to do simulations to confirm that.
Thanks,=20
Dagmara
=20
On 7/20/05, Indira Gazula <igazula@xxxxxxxxxxx> wrote:
> Hi All,
>=20
> I have recently stepped into the world of SI and would appreciate any inp=
uts on my question:
>=20
> I am working on the interface between a QDR-II SRAM and Processor (163 Hz=
clock, 1.5V). The suggestions for this interface is that trace length shou=
ld not exceed ~3000mil. This particular interface has a shunt resistor of 5=
0Ohm to 0.75V on the QDR side. Simulations suggest longer trace lengths giv=
e acceptable performance for much longer trace lengths. Could anyone please=
explain why it is suggested that trace lenght should be restricted to 3in,=
also how it would be different if there is no shunt termination (is it req=
uired).
>=20
> Thanks in advance for the help.
>=20
> Best Regards,
>=20
> Indira.
>=20
>=20
> ---------------------------------
> Free antispam, antivirus and 1GB to save all your messages
> Only in Yahoo! Mail: http://in.mail.yahoo.com
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>=20
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>=20
> List technical documents are available at:
> http://www.si-list.org
>=20
> List archives are viewable at:
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>=20
>=20
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
