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From: bmhochberg@watnot.UUCP
Newsgroups: comp.sys.cbm
Subject: Using RS-232 & Serial Bus Simultaneously
Message-ID: <12799@watnot.UUCP>
Date: Sat, 4-Apr-87 16:10:58 EST
Article-I.D.: watnot.12799
Posted: Sat Apr  4 16:10:58 1987
Date-Received: Sun, 5-Apr-87 10:23:53 EST
Reply-To: bmhochberg@watnot.UUCP (Bryan M. Hochberg)
Distribution: na
Organization: U. of Waterloo, Ontario
Lines: 30


---

	When I originally purchased my Commodore 64, I was under the
impression that the RS-232 and the serial bus could not be operated at the
same time due to competing NMI's.  My understanding was that to download a
file from the modem, you had to hold the downloaded file in memory.  Upon
the end of transmission, the RS-232 device was closed and the file was
written to disk.  If necessary, the modem was then re-opened.  I knew that
this problem did not exist if the disk drive was hooked up through an IEEE
cartridge.

	Now that I have my 128 and a better modem (1670), I've been doing a
lot more telecommunicating.  Of the software I have, various up/download
protocols are supported (i.e. Punter, XMODEM, etc.).  What I have noticed,
though, is that the disk file is opened at the start of the file transmission
and is written to while the file is being transmitted over the modem.

	Can anybody explain how this simultaneous modem/disk activity is
possible?


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Bryan M. Hochberg             UUCP:  {abunchasystems}!watmath!watnot!bmhochberg
U. of Waterloo, Ont.          MAIL:  P.O. Box 460 E4-201
                                     Waterloo, Ontario
                                     N2J 4B6
                              BELL:  (519) 884-7527
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"Don't let your schooling interfere with your education." - Mark Twain