[Coco] How SLENB works ?

[Matthew Stock]

The R/W line controls the direction of the data bus pins, and the DATAEN
line from the header controls the tristate mode of that bus.  For all the
other pins (address and control lines), they are always enabled and Coco ->
header direction.  That isn't perfect for all use cases, but it kept the
wiring simple.

The shield board uses a different method of connection, using several
74CBTD3384CP
 devices.  In this case the directionality is automatic, but I have the
signal lines grouped into 4 "banks" either enable or tristate.  It's a
little more general purpose than the first design, but it is also more
complex.  If you're interested in this one, I'll put a copy of the
schematic up that matches the board layout on OSHPark.

Matt



On Sat, Jul 19, 2014 at 11:03 PM, Luis Antoniosi (CoCoDemus) <
retrocanada76 at gmail.com> wrote:

> interesting the high density buffer, but how do you control the buffer
> direction ? Through the R/W pin ? What about the addresses lines they
> shouldn't be reversed even in a read operation, only when the processor is
> halt that you could take control of the bus, right ?
>
> Luis Felipe Antoniosi
>
>
>
>
> On Fri, Jul 18, 2014 at 11:46 AM, Matthew Stock <stock at bexkat.com> wrote:
>
> > I did the same thing.  I already built a high density 3.3v buffer for the
> > bus (http://www.bexkat.com/coco/DE1%20Coco%20Adaptor.pdf), so that part
> > wasn't an issue with the Due or with any other 3.3v logic I wanted to
> throw
> > into the mix.
> >
> > I actually have a shield design for the Mega that has all the buffer on
> it
> > too.  If anyone's interested in the schematics, let me know.  It was a
> bit
> > of a hack for my own needs, but it will do the job.
> >
> > I'm not producing these boards any longer, but you can order them via
> > OSHPark if you want: https://oshpark.com/profiles/mattstock.
> >   -Matt
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> >
>
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