Date   : Wed, 08 Oct 2003 20:23:10 +0100 (BST)
From   : Pete Turnbull <pete@...>
Subject: Re: XFER v4 problem

On Oct 8, 17:30, David Devenport wrote:
> I don't know if this helps, but when I wrote my emulator I linked my
pc
> to BBC via a serial cable,
> the BBC could talk (transmit) to the PC fine, but WOULD NOT under any
> circumstances receive anything
> transmitted from the PC. I put this down to the different voltage
levels
> from RS232->RS423.

It won't be voltage levels (at least, not in the sense I think you
mean).  I've had PCs "talking" to Beebs, and so have many other people
I know.  It's more likely a handshaking issue.  I bet your PC simply
wasn't sending any characters (or you'd failed to cross over RxD and
TxD).  The voltage level put out by the PC will be higher than the
nominal +/- 5V used by the Beeb's RS423, but that won't bother the
Beeb; equally, since the *thresholds* for RS232 are quite low (around
+/- 3V) the Beeb's RS423 will be perfectly acceptable to any normal PC
serial line.  RS423 was deliberately designed to be compatible with
RS232.

So far I don't think I've seen anyone mention kermit.  Lots of PC
software supports kermit protocol, which is fairly bulletproof;
MS-Kermit for DOS (and which runs under Windows in a DOS/command
window) is still free for personal use.  Similarly, kermit for the BCC
is readiliy available, either as a sideqays ROM image or a file to run
in RAM, and is also built in to several terminal emulation packages for
the Beeb.  You still need the handshaking lines sorted though!

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York