[TI-H] Re: TI Networking.

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[TI-H] Re: TI Networking.



On Wed, 02 May 2001 21:40:31 +0200 Olle Hedman <oh@hem.passagen.se>
writes:
> 
> At 21:01 2001-05-02, you wrote:
> >Even at byte level, it only works with 2 calculators.  Each line
> >transition requires a response from the other end.
> 
> no? what kind of response?

One bit is sent like this:

Sending calc brings red line low
Recieving calc brings white line low
Sending calc brings red line high
Recieving calc brings white line high

(or swap white/red)

> >That seems strange, the 68k calcs have more processor power to 
> spare...
> >Oh well, no use trying to figure out TI's motives ;)
> 
> You'll have to take my word on this :)

Oh, I believe you, I just think it's strange ;)

> would probably be more tricky with this scheme on the z80 calcs. I 
> remember 
> now of very limited interrupt architecture. Probably isn't a good 
> idea with 
> interruptdriven on thoose.

Yes, interrupts are basically key press and ~200/s periodic.

I think in games interrupt driven is still the best way, just limit
transfer rate on that.  When full speed is required, full attention must
be given to the link port.

> >True, I was suggesting a fixed length to keep packet size small.  A 
> byte
> >indicating packet size is a byte not carrying data.
> 
> yes.. maybe it is overkill.


I think variable length might be good if you could allot less that a
whole byte to indicating length, but that can be hard to do.  You could
have an end packet marker rather than a start packet marker and use that
to determine packet length as well.

And if you're going to ignore z80 calcs anyway, you may want to still use
a full byte for packet length.

> That depends entirly of what you have on the bus. if it is a temp 
> sensor, 
> you would almost only read.
> a multiplayer game would have more writes though, probably. read 
> status of 
> all calcs, and then write to the others. hmm.. lot of work for the 
> master...
> would be nice with no master, but collision detection is tricky.

You could have it turn based, each calc takes turns being the "master". 
Each calc would need to know how many others are out there, then every n
packets sent, it sends one (whether or not it has anything to send). 
Similar to token ring, but on a shared medium.

> sounds like the z80 calc owners have even more problems doing any 
> good 
> networking then I with a 68k calc...
> If I do anything, I will probably focus on 68k...

No to mention restrictions on memory and overall processing time.  I very
much doubt you could write a game on the z80 calcs that would require
that much data to be exchanged.

-josh
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