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Old 04-15-2006, 12:45 AM
Jim Granville
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Default Re: humble suggestion for Xilinx


John Larkin wrote:
>
> Since the max serial-slave configuration rate on things like Spartan3
> chips is, what, 20 MHz or something, you might consider slowing down
> the CCLK input path, and/or adding some serious hysteresis on future
> parts. On a pcb, CCLK is often a shared SPI clock, with lots of loads
> and stubs and vias and such, so may not be as pristine as a system
> clock. CCLK seems to be every bit as touchy as main clock pins, and it
> really needn't be.


Wouldn't one expect this to be 'normal design practise' ?

I suppose Xilinx missed that obvious feature, becasue there are no
other Schmitt cells on the die, and even tho the CPLDs have this,
I'm sure their inter-department sharing is like most large companies

-jg

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