[SI-LIST] Re: Rise/Fall time Vs Bit rate.
- From: Tesla <emcesd@xxxxxxx>
- To: weirsi@xxxxxxxxxx
- Date: Tue, 28 Aug 2012 18:00:37 +0800 (CST)
Hi, Steve
Thanks a lot
Would you give a link about the intel paper you mentioned? Be interested to
read it.
Regards.
Tesla
At 2012-08-28 16:15:37,"steve weir" <weirsi@xxxxxxxxxx> wrote:
>If one is dealing with data signals, then as long as they settle out at
>valid logic levels by the time they are sampled, and remain stable long
>enough to satisfy hold time requirements, then all is good. That
>observation has lulled many a digital engineer into "Sauron's Happy
>Fun-Time Intermittent Failure Party at Mount Doom"(tm) when they neglect
>the fact that not all low-rate signals are data. Some low-rate signals
>are timing strobes, such as TCLK on a JTAG bus. Timing strobes not only
>have to settle-out at valid levels, they need to be free of waveform
>artifacts like double transitions.
>
>Then there are high impedance dinosaur busses that say: "Hey sailor:
>For $20 dollars I'll take your induced noise around the world." A few
>years ago Intel presented a DesignCon paper where they described
>spending the better part of a million dollars on manpower and
>sophisticated software tools, as well as nearly half a year tracking
>down signal integrity problems on a lowly I2C bus. Every month or two
>induced noise would cause servers to reset.
>
>Steve.
>
>
>On 8/28/2012 12:23 AM, Rohit MISHRA wrote:
>> Rajneesh,
>>
>> That's a good question, indeed !!
>>
>> You rightly pointed out that slow repetition pulses driven by fast driver
>> can also have reflections & other transmission line effects but you should
>> also understand that these effects create signal integrity problems most
>> when they have less time to settle.
>>
>> The signal pulse width and duty cycle are not factors in deciding
>> transmission line behavior such as reflections but when you use high pulse
>> width i.e. low bit rate signal, you are also giving more time to settle
>> these effects before sampling at receiver end and remember, what the signal
>> looks like at sampling that matters most !
>>
>> Hope that helps.
>>
>>
>> Rohit Mishra
>>
>>
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>> Behalf Of rajneesh shukla
>> Sent: Tuesday, August 28, 2012 12:29 PM
>> To: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Rise/Fall time Vs Bit rate.
>>
>> Experts,
>> We all have read that in high speed design it's rise time that creates
>> signal integrity issue. By this theory, all low bit rate signals that
>> is driven by fast I/O driver will also have signal integrity issues then
>> why most of the time high bit rate signals are analysed for signal
>> integrity issue ??
>>
>> Please explain what is the role of bit rate in signal integrity ??
>>
>> Rajneesh
>>
>>
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>
>
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>Steve Weir
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