24 Nov
2000
24 Nov
'00
3:18 a.m.
On Nov 23, 22:35, Richard Erlacher wrote:
It's been a long time since I last put together a
coax board uisng a
DP8392
transceiver, but as I recall the 8392 needed
relatively few external
devices. Its purpose, however, was to drive the coax. I don't believe
there's any need for it in a TP application.
Well, no, you use a different transceiver IC for that, with a differntial
output, differential input, and some capacitors for pulse-shaping.
In the classic ethernet/thinnet board design, there
was a controller,
e.g.
AMD 7990, a modulator/demodulator, e.g. AMD 7992,
often with the digital
pll
right in it, and a coax driver like the 8392, but, in
AMD's case it was
another device with more pins and more external parts.. The
modulator/demodulator drove the AUI outputs, OR, if jumpered
appropriately,
drove the DP8392. The DP8392 was also the most costly
of the three or
four
popular coax drivers, (AMD, Intel, National, and SEEQ)
but it was worth
it
because of its smaller package size and need for fewer
external
components.
I have a few boards (at least one ISA for a PC, and some Acorn cards) which
use the Intel controller and SEEQ. My experience (and that of some others
I've talked to) is that the Intel/SEEQ combination is much less reliable
than the AMD/National ones. It's also much harder to get the ICs for if
you need to repair one.
--
Pete Peter Turnbull
Network Manager
Dept. of Computer Science
University of York