Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!tdatirv!pa1
From: pa1@tdatirv.UUCP (Pat Alvarado)
Newsgroups: comp.os.cpm
Subject: Re: Osborne 1, Questions Answered
Keywords: Osborne 1 Disk Drive Thanks
Message-ID: <7@tdatirv.UUCP>
Date: 28 May 91 14:59:42 GMT
References: <1991May23.042256.12302@actrix.gen.nz>
Reply-To: pa1@tdatirv.UUCP (Pat Alvarado)
Organization: Teradata Corp., El Segundo, Ca.
Lines: 19

In article <1991May23.042256.12302@actrix.gen.nz> ewen@actrix.gen.nz (Ewen McNeill) writes:
>The verdict on the serial port and modem port appear to be that they are
>the same control lines inside the machine.  The RS232 port apparently is
>only TTL levels, so some line driver/receivr chips would be needed.
>Speed choices are 300 and 1200, although there is apparently a link
>inside which can make this 600 or 2400 (from IMP overlay).
>

The Osborne 1 uses the standard 1488 and 1489 chips to the external port
of the RS232 interface, and uses +/- 12VDC to drive the signals. The speed
of the RS232 port can be software selectable between two speeds. There is
a way to strap the clock chip to allow up to 4800/9600 bps operation.
This information is from my Osborne 1 Technical Reference Manual,
which indicates on the schematic how to strap the clock chip.
-- 
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