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Path: utzoo!linus!decvax!duke!mcnc!dvamc!sfw
From: sfw@dvamc.UUCP
Newsgroups: net.micro.cbm
Subject: RS-232???
Message-ID: <1110@dvamc.UUCP>
Date: Fri, 6-Jan-84 02:30:29 EST
Article-I.D.: dvamc.1110
Posted: Fri Jan  6 02:30:29 1984
Date-Received: Sun, 8-Jan-84 21:40:43 EST
Lines: 23


CBM vs RS232 Peripherals
	Connecting any RS-232 device to the 64 or VIC
is an exercise in frustration if not futility.  CBM
managed to totaly mung the implementation of RS-232
in such a way that it is impossible to reliably use
the serial port devices such as printer and disk while
using the RS-232 port.
	This is due to the fact that the RS-232
software UART uses the NMI and the serial port software
UART uses the NMI as well.  The guru's of Commodore did
not see fit to interface the two properly to eliminate
bus conflicts.  The only way I have found around the
problem is to buffer the input from the RS-232 into
RAM and then print out the contents to printer or disk
when the RS-232 is guaranteed quiescent (i.e.
the host program is waiting to receive input from
the VIC or 64).
	If anyone else has had similar difficulties
and/or alternative solutions to this problem your
input would be most welcome.
			Sue F. Woodbury
			(duke!dvamc!sfw)