[SI-LIST] Re: Cmos I/O & GTL I/O
- From: Sunil Chandra KASANYAL <sunil-chandra.kasanyal@xxxxxx>
- To: steve weir <weirsp@xxxxxxxxxx>
- Date: Mon, 17 Nov 2003 13:46:43 +0530
Steve, You are right but in general series terminated IOs are not
PREFFERED for multi drop operation, because the receiver connected at
the mid point of the Tx line will receive proper signal after one
reflection at the end of the transmissin line. So, the total signal
delay for the receiver at mid point= 1.5*(Tx line delay).
steve weir wrote:
>
> Sunil, mostly.
>
> Source series terminations can be used with multi-drop busses. PCI is a
> prominent, if somewhat ill-conceived example due to drivers mid bus.
>
> Regards,
>
> Steve.
> At 01:19 PM 11/17/2003 +0530, Sunil Chandra KASANYAL wrote:
> >Partha,
> >
> > 'Source terminated CMOS I/O' means the IO whose output impedance is
> >equal to the transmission line impedance for matching at the source end.
> >It is not necessary to keep the output buffer impedance equal to the
> >trasmission line impedance, but the matching can be achieved by
> >providing a resistance at source end. If your driver has perfact
> >matching with transmission line than this architecture will be same as
> >the series terminated case.
> > GTL has the open drain architecture of output buffer having very
> > high
> >current sinking capability. GTL IO is terminated at the receiver end of
> >the transmission line.
> > In source terminated case, signals are terminated at source end
> > after
> >reflection at receiver end, but in case of GTL, signal is terminated at
> >the end of the transmission line and no reflections will be there if
> >termination is proper.
> > CMOS IOs are generally used for lower frequency of operation which
> > is
> >about 50 to 60 MHz. GTL IOs are used for backplan operation where driver
> >current capability is required very high (about 40mA).
> > Also, source terminated IOs are not preferred for multidrop
> > application
> >but if termination is at the receiver end, IOs can be used for multidrop
> >operations.
> >
> >Am I right ??
> >
> >Thanks and Regards,
> >Sunil C Kasanyal
> >
> >
> >-------------------------------------
> >Hi all,
> > What does it mean when one says 'Source Terminated
> >CMOS I/O'? How is it different compared to GTL(Gunning
> >Trancsiever Logic I/O) and what are their advantages &
> >disadv when compared with each other?
> >
> >Thanks in Advance,
> >
> >Regards,
> >Partha!
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--
______________________________
Sunil C Kasanyal
STMicroelectronics Ltd.
Noida INDIA
Ph.No.:+91-120-2512021/30
+91-120-2515262/64 Extn:6924
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