Re: Slot 'extender' dev cable

["mdj" <mdj.mdj@gmail.com>]

On Jan 31, 7:25 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:

> Unfortunately, the answer is "It depends."

There goes my hope that you were going to say "the ESR and capacitance
of IDC ribbon is sufficiently low that all but the most aggressive
card designs should work fine" ;-)

> If you have few cards plugged into your development machine, and
> those that are present put only a modest load on the address and
> data busses, a 2- to 3-foot extension cable is probably workable.

Actually the dev machine is as unexpanded as I can get it - just a
Disk II card and an old Atlas 40 tracker, plus one of the miniaturised
late model extended 80 column cards.

I am somewhat paranoid about plugging in stuff I've designed with
harder-to-source peripherals until I've proven my design operates as
expected.

> The danger is that it will inevitably alter the risetimes and
> falltimes, and add several nanoseconds of delay.  You may wind up
> with your design being dependent on these timing modifications,
> and being marginal when directly inserted into an Apple II.

Hopefully, several nanoseconds won't bother this design, which is
effectively an asynchronous, buffered two way communications setup -
so there's really only a couple of transceivers and latches, and a
tiny bit of address decode logic.

> Of course, if your timing design is conservative, that wouldn't
> be a problem--but it's sometimes hard to know.  ;-(

Well, when the CRO shows up I'll see if I can measure the propagation
delay of the cable. I'll let everyone know.

Cheers,

Matt