11 Nov
1999
11 Nov
'99
9:59 p.m.
On Thu, 11 Nov 1999 23:50:39 +0000 (GMT) Tony Duell
<ard(a)p850ug1.demon.co.uk> wrote:
> > Pick your favourite serial chip. Link it to
the T2 bus, using a PAL for
> > address decoding and/or to fiddle the R/W .vs. Wr/ and Rd/ signals.
> > That's about it.
This is precisely what we had to do at my previous company.
We needed four serial ports on a TRAM, but none of the
commercially-available ones were any good. Some were
really awful "bit-banging via an 8-bit latch" designs,
others had a Z80 CPU and a link adaptor, others would do
just 3-wire RS232 with no modem control.
You've almost convinced me to have a go... It
won't be T2 based, as I
don't have any spare (or socketed) T2s... I may have the odd T4 in the
junk box, though. Any preference on the serial chip I use, or should I
just use a 8250 or something?
We used a quad UART from the RS Components catalogue. You
can get 8-way UARTS! I think Philips/Signetics do them.
Dunno when I'll have time to do this (and if
somebody beats me to it,
fine :-)), but it just might be something for me to try...
I don't have the circuits any more, but it was really
straightforward. Just a T222, the UART, some MAX232s, some
SRAM, and glue logic (about four 74xx MSI chips). All went
on a size two TRAM fairly easily.
-tony
--
John Honniball
Email: John.Honniball(a)uwe.ac.uk
University of the West of England