[Coco] Fwd: IP packets on my coco

[John W. Linville]

On Thu, Jun 09, 2016 at 10:34:12PM -0400, John W. Linville wrote:
> On Thu, Jun 09, 2016 at 08:19:43PM -0500, RETRO Innovations wrote:
> > On 6/9/2016 12:36 PM, John W. Linville wrote:
> > > https://www.cirrus.com/jp/pubs/proDatasheet/CS8900A_F5.pdf
> > > 
> > >  From page 77:
> > > 
> > > 4.10.9  Basic I/O Mode Receive
> > > 
> > > I/O Mode receive operations occur in the following order (In this
> > > example, interrupts are enabled to signal the presence of a valid
> > > receive frame):
> > > 
> > > 1)  A frame is received by the CS8900A, triggering an enabled
> > > interrupt.
> > > 
> > > <snip>
> > > 
> > > That looks fairly clear to me.  Is the datasheet wrong?
> > I don't think it is wrong, but maybe it is incomplete.  Numerous developers
> > in the 64 side have lamented the lack of IRQ capability in IO mode.  I will
> > check to see where they got their information.
> 
> Well, it looks like the datasheet might be wrong...
> 
> Application Note 181 from Cirrus Logic says:

https://www.cirrus.com/en/pubs/appNote/an181.pdf
 
> "Unsupported functions in 8 bit mode
> 
> - Interrupts are not supported. Polled mode must
>   be used.
> 
> - The DMA engine only uses 16 bit memory ac-
>   cesses and does not support 8 bit transfers.
> 
> - The packet page pointer has an auto increment
>   feature that cannot be used in 8 bit mode.
> 
> - An EEPROM is not supported.  Most 8 bit de-
>   signs should not require one and can eliminate
>   the added cost."
> 
> And Application note 205 says:

https://www.cirrus.com/en/pubs/appNote/an205-2.pdf

> "1) Application Note 181 says that interrupts are not supported
> in 8-bit mode. Is this really true?
> 
> Yes, interrupts are NOT supported in 8-bit mode. They might appear
> to work for a while but will eventually fail."
> 
> So apparently the 8-bit mode is a bit unreliable in the CS8900A?
> 
> With that said, the usefulness of interrupts for servicing an Ethernet
> NIC on <2MHz CPU is debatable...
> 
> John
> -- 
> John W. Linville		Someday the world will need a hero, and you
> linville at tuxdriver.com			might be all we have.  Be ready.

-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.