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From: porter@cbmvax.cbm.UUCP (Jeff Porter)
Newsgroups: net.micro.cbm
Subject: Re: 2400 baud modems
Message-ID: <604@cbmvax.cbmvax.cbm.UUCP>
Date: Sat, 9-Aug-86 22:21:10 EDT
Article-I.D.: cbmvax.604
Posted: Sat Aug  9 22:21:10 1986
Date-Received: Tue, 12-Aug-86 10:05:59 EDT
References: <2050@watmath.UUCP> <865@usl.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 19

> In article <2050@watmath.UUCP> grwalter@watmath.UUCP (Fred Walter) writes:
> 
> Actually, what is needed is a hardware UART. I have diddled with
> perhaps taking an Intel chip and hanging it off the user port, using
> the timer as the bit clock, but haven't attempted it yet. A 6800/6500
> family chip would be very difficult to hang off the user port, since
> it would be a synchronous chip (needing a 1 Mhz. clock to operate and
> expecting its operands within that clock).
> 

What you need to do is hang the UART off the CARTRIDGE PORT not the
USER PORT.  A 6551 will do nicely.  You will however need to write
your own software to look at this different location for the UART.
This UART is software selectable to 19.2K baud, but I will wager
that you run into crunching power before this (esp. with a smart
terminal emulator).

Jeff Porter
Commodore Engineering