[Coco] WiFi modem.

[Gene Heskett]

On Saturday 20 January 2018 12:38:16 RETRO Innovations wrote:

> On 1/20/2018 2:12 AM, Gene Heskett wrote:
> > I don't recall writing the above, Jim.
>
> Yep, I forgot to clean out the attrib line.
>
> > I've not been advised what the
> > differences are between the 65C51S and the 65C51N that I can get
> > from the likes of Mouser.
>
> Both are the 65c51N from Western Design Center.  There are two
> variants.  S version and N version:
>
> https://en.wikipedia.org/wiki/WDC_65C51
>
> Note that one or both 65c51N variants have a serious transmit register
> bug
>
> http://forum.6502.org/viewtopic.php?f=4&t=2543&start=90
>
Wow, thats a showstopper bug IMO. That chip, if they think they can 
peddle that production run before shipping a fixed one, is simply the 
end of that chip. I saw mention of other duarts there, maybe you should 
be looking at them instead.

> > Obviously for new designs, one should use the
> > smaller square version packaging, but does that lend itself to
> > piggy-backing like the minidips for a poor man's dual port?
>
> Not really.  PLCC cannot easily be straightened.
>
> > I again do
> > not know if tsop legs can be straightened to stack them. It may be
> > that with the modern packaging, just lay out a 2nd pattern so that a
> > 2nd chip can be added later if a dual port is needed,
>
> This would be preferred.  And,it's no big deal to lay out a second
> ACIA on the PCB.
>
> Jim

From the tone of the last message in that thread, it agrees with mine. 
Sounds like the NXP SC28L92 might be a far better deal. But again I've 
no clue how much support glue other than cs decoding it might need. If 
the crosslink is followed, there are pdf's available there for these 
chips. QFP44. 10mm sq. looks like a good package choice. Theres also 
some sync logic glue samples in one of those messages.

So theres one out, to get away from a WDC design that was broken from the 
gitgo and even the latest, available for sale chips are STILL broken.

Besides, the selectable 8 or 16 byte deep fifo's of the 28L92 would solve 
a lot of the speed problems.

Please take a look at it when you come up for air Jim, I think you'll 
like it, and the QFP44 packaging looks like a toaster oven reflow would 
work nicely. Getting rid of some pretty pickity hand soldering.

I've no clue if NXP is making a 6551 clone thats not broken, but the 
fifo's in this chip would certainly be an advantage.

Cheers, Gene Heskett
-- 
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