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From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.dcom.modems
Subject: Re: Why no PC modems without UART (re: Beware the Telebit T18pc)
Summary: There's more to the UART than that.
Keywords: uart chip emulation modem
Message-ID: <23491@netcom.COM>
Date: 10 Feb 91 07:09:35 GMT
References: <1991Feb9.022024.10932@wsrcc.com> <23314@netcom.COM> <6v#qh2.o+3@smurf.sub.org>
Followup-To: comp.dcom.modems
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 38

In article <6v#qh2.o+3@smurf.sub.org> urlichs@smurf.sub.org 
(Matthias Urlichs) writes:
>< 
>However, when you know what's on the other side of the pseudo-UART (a Telebit
>modem, in this case), you can forget about almost every feature.
>

Sure *I* know what's on the other side of the UART.  It's the *software*
that has no idea what modem is there (or if there's even a modem there).
If the comm software or tty driver assumes that it's a Telebit modem,
then it must be a specially written driver, right?  Yes, special hardware
can be supported by special software, but then the hardware isn't very
compatible anymore...

>
>All you need is bits&parity (baud rate for the "use speed of last AT command"
>modes only), handshake lines, and send+receive buffer.
>
>Seems reasonable to me.
>

A favorite software program had a "fortune cookie" function that sometimes
said "'Easy To Use' is easy to say".  A UART isn't really as simple as that.

>
>However, it still has to be implemented&programmed&tested, and it might be
>more cost-effective to just stick two cheapo UARTs (one for the PC, and one
>for the modem -- you already have the software for the latter from your
>standalone modem PROMs) onto the board instead of the latches you'd otherwise
>need.
>

Agreed, for the reasons I mentioned in my last posting.

-- 
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| Greg Andrews      |   gandrews@netcom.COM |
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