Date   : Wed, 27 Jul 2005 17:04:06 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Econet-Ethernet bridge

On Wed, 2005-07-27 at 15:00 +0000, Jules Richardson wrote:
> On Wed, 2005-07-27 at 15:50 +0200, Johan Heuseveldt wrote:
> > So, Econet for Beebs is at max 200 kHz, which is bit speed. Byte speed
> > will then, lets say, 20 to 25 kHz. (20/10, 20/9, 20/8)
> > Is that (really) a problem for parallel/Centronics?
> 
> I *think* you can get about 100KB/s through a parallel port, so it
> sounds like that *could* work comfortably with buffering at the byte
> level.
> 
> Just depends whether it's possible to work at the byte level across that
> interface boundary - which depends on the nature of the Econet protocol
> itself (if it needs to work at the bit level at any time then control
> via the parallel port - operating at byte level - might be difficult)

I just grabbed the 68B54 datasheet, and it looks like the whole thing is
byte-accessed anyway, and the chip itself handles
serialisation/deserialisation to/from a bit stream. 

Main problem might be the lack of output lines (other than the 8 data
bits) of a parallel port - seems like the 68B54 needs quite a few
control lines as well as the data bus: RS0, RS1, R/-W, -RESET, -CS, and
E.

(although I think E can just be a free-running local clock, and it
*might* be possible to hold -CS permanently active)

cheers

Jules