> And if the 2-computer case is very important, you can always make a single
> cable connecting 2 nodes. But it won't work for larger networks and it
isn't
> really JoyNet, just partly compatible. I think Laurens even has the
schematic
> for the 2-computer cable on his JoyNet page.
Yes, it's there.
> > > Another problem is the granularity of the waiting loops. If you want
to
> > > avoid self-modifying code, the fastest waiting loop is DJNZ, which
takes
> > > 9 cycles for the last loop and 14 cycles for the other loops. So if
you
> > > want to wait 10 cycles, you'll have to round to 23.
> >
> > Timing must indeed be thought of. There is no need to round. Loops that
> > are the same every time can easily be coded.
>
> Using JP instead of DJNZ, the number of cycles per loop can be made
constant.
> But it's not possible to get every number of cycles (try 6). Nor is it
> possible to have any fine-grained control without using self-modifying
code.
> And apart from being complex, self-modifying code doesn't work in
read-only
> memory.
I made a SiMPL sample-player once, which (before playing the sample)
'calibrated' itself (see how many samples can be played within an
interrupt). If it was too fast, a <unit>-long wait was inserted. Repeat
until too slow. Then lower <unit> by, say, a factor ten, and start
decreasing the wait until it's too fast again, and so on until <unit> has
reached the minimal quantity.
I used NOPs to wait, since it's the most precise unit. They were inserted
into the code (so the part after the NOP waits was relocatable). It's a bit
complex, but accurate.
> You wouldn't have to design the IP layer, because it already exists. We
only
> have to find out what the minimum packet size is and whether using IP in a
> JoyNet network will work in practice.
>
> I don't know much about IP either, but Adriano Camargo Rodrigues da Cunha
> knows (and implemented it in UZIX) and Laurens Holst is now learning (and
> implementing) it. Guys, please enlighten us.
Pfff... It's really very simple. An IP packet consists of a header (with a
good and fast-calculated checksum) and some data. However I suggest to use a
simpler protocol. The IP-address for example is 32-bits. You only need 8
bits in this case. And it contains some other parameters which are
absolutely not nessecary, and if they are they can be passed as options, not
as a part of the default header.
Look at ftp://ftp.funet.fi/rfc/rfc791.txt
That's the IP documentation.
~Grauw
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