On Fri, 08 Sep 2000, you wrote:
> > JoyNet singal propagation doesn't need waits that long. On 3.5MHz I got
> > speeds of about 3.5 kilobyte per second, that is 3500*8=28000 bits per
> > second, which is 125 clocks for a total 1-bit cycle (data + ack). Given
> > the fact that there are quite a few instructions executed for every bit,
> > there is hardly any waiting at all.
>
> In that case I am truely convinced that the unidirectional solution is
> also the quickest (given the joynet hardware).
There is one thing that takes a lot of time in the non-timed protocol:
because the ack should be read for every bit written (reverse read and write
if you're receiving instead of sending), you constantly have to switch
between PSG register 14 and 15.
In a timed protocol you only have to read ack once in a while. I think a
timed protocol can be quicker, but it's just too complex to get it working
correctly on all possible configurations.
> > For Linux, the best solution would be to write a serial driver for
> > JoyNet. Then pppd can be used to connect to UZIX and you can use the
> > existing PPP network device.
>
> Not at all. Linux knows the `network driver' as a special object. I should
> just write a network driver, so the parallel port is treated as a network
> device. Then you can just use the connection as if it is an ethernet card
> , which means there is no need for a point to point link. It also means
> that UZIX will need to use 4 byte host addresses (actually interface
> addresses), at least in the JUMP driver.
One advantage of PPP is that there are very little modifications necessary in
UZIX. Another advantage is that host configuration can be done using PAP. If
JUMP is treated as ethernet, UZIX has to be configured manually or we would
have to write a DHCP client for it.
> > You can also make a user-mode solution, that sends stdin over JoyNet and
> > sends JoyNet input to stdout. That program can then be connected to pppd
> > using pipes. It's less flexible than a kernel driver, but it's also
> > easier to write
>
> Not at all. Just hacking the plip driver is done in a few minutes.
Are you experienced or optimistic? ;)
Bye,
Maarten
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