Re: CIA old/new?

From: Segher Boessenkool <*segher_at_kernel.crashing.org*> Date: Wed, 6 Jan 2021 21:12:03 -0600 Message-ID: <20210107031203.GI30983_at_gate.crashing.org> · segher_at_kernel.crashing.org

On Wed, Jan 06, 2021 at 08:27:29AM +0100, Gerrit Heitsch wrote:
> On 1/5/21 10:27 PM, peter_at_rittwage.com wrote:
> >This has been tested to fix the issue with a cap on the CS line? I'll 
> >have to try it.
> >
> >It seems like I've put HMOS VIC-II into an older board (fixing the 
> >voltage issue) and it had the dots, but that may not matter, as you 
> >mentioned.
> >
> >I assume this is the line that goes from CS to the "VIC" pin on the new 
> >PLA on a 250469? Trace cut and put cap between them?
> 
> No. You'd have to put a cap between the /CS on the VIC and GND.

Yup.  Just a low-pass filter, used as a crappy delay.  I would put it
close to the pin on the VIC, but that may not matter much.

> You shouldn't do that though.

We only did it to show what causes the problem, yup.

But would it even cause any problems?  You're only delaying #CS by 40ns
or so (if you do it right ;-) ), that's well within allowed timing, it
just avoids the annoying light-grey blips.

(Not that I think people should do this!)

Segher