[Arm-netbook] libre 64-bit risc-v SoC

[mike.valk at gmail.com]

2017-05-29 23:24 GMT+02:00 David Niklas <doark at mail.com>:

> On Mon, 8 May 2017 06:24:08 +0100
> Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
> > On Mon, May 8, 2017 at 4:00 AM, David Niklas <doark at mail.com> wrote:
> <snip>
> > >> > important to avoid, because mixed analog and digital is incredibly
> > >> > hard to get right.  also note that things like HDMI, SATA, and even
> > >> > ethernet are quite deliberately NOT on the list.  Ethernet RMII
> > >> > (which is digital) could be implemented in software using a minion
> > >> > core.  the advantage of using the opencores VGA (actually LCD)
> > >> > controller is: i already have the full source for a *complete*
> > >> > linux driver.
> > >
> > > Considering that analog was around *long* before digital I'm surprised
> > > that it is "Hard to get right",
> >
> >  analog isn't "hard".  digital isn't "hard".  specifically *MIXING*
> > them is ultra-hard.
> >
> > > is there a reason for this?
> >
> >  completely different processes and design criteria.  the restrictions
> > (design rules) placed on digital ASIC layouts have to be adhered to in
> > the *analog* areas: you can't just change the stack to suit the analog
> > areas.  i don't know the full details, but i know someone with 30
> > years experience of working with ASICs who does.
> >
> > > Isn't there a chip for just this kind of thing?
> >
> >  no.  not a custom one... and we're taking custom ASICs.
>
> Forgive me for contradicting you again, but don't all computers that have
> a MIC in jack using some sort of analog to digital converter?
> And vice-versa with Headphone out?
> I think they all use PCM.
> Would such a converter be suitable? Why?
>

Crosstalk

Plug in your headphones in a laptop and listen to computer hard at work.

The speed of current digital signals makes them behave like analog signals.
And as such analog signals interfere with the digital signals.

With cables you can use shielding to mitigate that. On PCB's and inside IC.
That's a lot harder because of their stacked nature.


>
>
> Thanks,
> David
>
>
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