FreeLists / si-list / [SI-LIST] Re: 60MHz Bus: PCB trace length

[steve weir <weirsi@xxxxxxxxxx>]

300 mils only translates to about 60ps flight.  That a 60ps alteration 
on a 16,000ps cycle time bus makes a significant difference points to 
gross problems.  Unless you have loaded your bus to death, the problems 
are much more likely signal quality than timing alignment.

Steve.
S Balaji wrote:
> Hi Guys,
> I have a 32-Bit processor interfaced to an ULPI tranceiver.
> The bus is at 60Mhz.
>
> One of the control signal from the processor (STP) is more in length by 
> 300mils w.r.t the clock.
> The total length of the line is 1700mils. No termination. Stripline 
> routing.
>
> If i set the STP pin at slow slew rate (Processor pin configuration), then 
> my USB communication fails. 
> The CRC is detected wrongly (Data is correct. )
>
> But if i set the STP pin at fast slew rate, it works fine.
>
> Question
> 1. Is 300mils increase a major factor? 
>     Set up time requirement is 4.5ns. I could not get any info on the rise 
> time.
>
> Regards
> Balaji S
>
>
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