[Coco] CocoNIC

[RETRO Innovations]

On 9/15/2016 10:23 AM, John W. Linville wrote:
> On Thu, Sep 01, 2016 at 07:10:46PM -0500, RETRO Innovations wrote:
>> Brett sent me some test code, and test 1 succeeded!
>>
>> I can talk to the cs8900a  (got the mfr and product ID bytes back)
>>
>> Next step is LED blinking, and then on to UDP!
> Speaking of which...is there any design/developer info for the card
> that go along with CoCoNIC? Memory map, schematics, etc? Please send
> me whatever you have.
>
> Thanks,
>
> John

The IC is a cs8900a, and the datasheet is here:


https://www.cirrus.com/en/pubs/proDatasheet/CS8900A_F6.pdf


Section 4.10, on page 75 is the place to start. You will access the IC 
via the I/O space, which allows "indirect" access to the address space 
via the 16 registers.

Specifically, the registers are mapped into the IO space at $ff4x.

That is the complete design.  It has no other functionality at present.  
Which, is an issue of itself, because the CPLD on the unit is woefully 
underutilized.  Thus, if you have additional thoughts around capability, 
I'd love to hear about it (I can get rid of the CPLD, but it helps with 
meeting timing requirements, and PCB routing, so it has some value 
already).  I can easily add a flash ROM, or RAM, or both, but...

<cue soothing music and flashback fade>

I had a lot of PCB space on the 64 version of this card when it was 
finally laid out, and so I decided to put an EPROM socket footprint on 
the board (it was not possible to make the board smaller and have 
buttons out the back, and you pay for PCB size, regardless of what is 
etched).  Then, I added a rotary switch on the back of the board to 
select banks. The idea was that someone would create a "boot" app that 
would autorun and load a custom kerrnal into the machine on boot, like 
NetBoot PCs.  I produced and started selling.  No one created such an 
app, but people continued to buy the optional socket and switch.  Other 
chastised me for not having a ROM to go in there.

<fade to present>

Now, 7 years later, no real ROM is present, and people *still* buy the 
optional rotary switch even though there is no way to use it without the 
ROM, and there is basically no ROM.

So, I am leery of putting a footprint and a ROM on board if there is no 
code to put in it.

But, happy to do so if warranted.

If Darren wanted to work with me to make a EtherFDC, that would work as 
well.   Currently, though, I am not knowledgeable enough on the FDC 
internals to go at it alone.

JIm

-- 
RETRO Innovations, Contemporary Gear for Classic Systems
www.go4retro.com
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