Re: Apple ][ using PC floppy

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

On Dec 29, 9:23 pm, "RedskullDC" <redskul...@oohay.moc.ua> wrote:
> "vladitx" <vlad...@nucleusys.com> wrote in message
>
> f202b5e8-6061-46b8-9009-42c15ec4dfca@b38g2000prf.googlegroups.com">news:f202b5e8-6061-46b8-9009-42c15ec4dfca@b38g2000prf.googlegroups.com...
>
> > On Dec 29, 12:18 am, Steven Hirsch <snhir...@gmail.com> wrote:
> > Your main problem will be the logic levels - Spartan3 is a 3.3V device
> > and is not 5V tolerant. And there are no level-shifters on the Starter
> > board.
>
> A cheap option for 3.3V<->5.0V conversion when you are playing with
> prototypes is:http://www.futurlec.com/Mini_Logic.shtml
> I'd recommend getting a couple, one for inputs, one for outputs.

Seems a bit of a waste that the /OE and T/R lines aren't exposed to
the headers :-S

> The S3 chip's 3.3V outputs will (theoretically) drive the inputs of the
> floppy
> drive correctly, though I would be wary of doing this without buffers
> unless you can be certain of the current requirements of each input on
> the floppy drive.

If driving TTL inputs is all you need, you can just put the relevant I/
O pins in open-drain mode and pull them up to 5v via a small resistor.

> Easy to turn you S3 board into a doorstop :)

You're pretty safe... using a '245 is only necessary if you want to
participate on a bus, which unfortunately those futurelec boards won't
let you do.

Matt