[Coco] Internet via Coco
cocowal6809 at gmail.com
Wed Jul 14 11:06:50 EDT 2010
On Thu, Jul 15, 2010 at 12:52 AM, James Dessart <skwirl42 at gmail.com> wrote:
> On Wed, Jul 14, 2010 at 11:34 AM, coco wal <cocowal6809 at gmail.com> wrote:
> > To some extent , you still need to bit bang your spi data to the ethernet
> > controller , a 'much simpler, hardware-wise' solution might be
> > slow and taxing processor wise how exactly did you plan on implementing a
> > coco bus to spi interface ? I assume you would like your packet data on a
> > 10Mb/s connection at a reasonable rate , and if under os/9 , being able
> > multitask as nicely as possible.
> Good point.
> The SPI driver would be for the enc28j60, yes. The one with the 32
> byte address space is the RTL8019, which I have on a bread-board
> compatible module. There's a uIP driver for it on the ATmega series,
> which is why I had chosen it. But with the CoCo's small IO space, 32
> bytes is a lot. So some sort of logic would have to be introduced to
> choose which address in that space through some sort of register.
> While I have an idea of how to do that, and could probably sketch out
> a basic block diagram, I have no idea how to properly implement that
> design physically as a card for the CoCo.
James , one idea which might be worth trying instead of bit banging or using
a serial link to a microcontroller might be to do something similar to the
way the SSC talks to its internal microcontroller. You could say setup some
decoded latches , one for write data , one for read data and another for
status . This could connect to a larger pinned atmel / microchip and form
a pseudo bus interface . You have extra overhead when reading and writing
since you need to check when the slave microcontroller has received data or
is read to send , but i think it would still be faster then bit banging a
few latches to implement SPI.
I have used the uIP on a 8K atmel in the past , it worked fine , just didnt
have the enough space to implement all that i wanted , but thats just an
processor selection issue.
And i didnt mean to sound discouraging in my previous email , I would love
to see what you are suggesting implemented , just playing devils advocate on
the issues you may face.
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