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From: kkim@uiucdcsb.cs.uiuc.edu
Newsgroups: comp.dcom.modems
Subject: 8-bit byte can be sent w/o xform ?
Message-ID: <167100015@uiucdcsb>
Date: Wed, 7-Oct-87 14:59:00 EDT
Article-I.D.: uiucdcsb.167100015
Posted: Wed Oct  7 14:59:00 1987
Date-Received: Sat, 10-Oct-87 18:18:53 EDT
Lines: 24
Nf-ID: #N:uiucdcsb:167100015:000:951
Nf-From: uiucdcsb.cs.uiuc.edu!kkim    Oct  7 13:59:00 1987


   as i understand, most 1200-bps modems send data in the unit of
seven data bits preceded and followed by some start and stop bits.
there is usually one parity bit which may or may not be used.

   it seems that one 7-bit ascii character is sent as one unit.
however, binary files which uses all 8 bits are usually transformed
before being sent - that is, 3 8-bit bytes are transformed to 4 6-bit 
units, slightly modified (adding some number to make it non-control
character), and then sent as 4 units, not 3.

   i wonder if there are any special 1200- or 2400-bps  modems that can
send 8-bit byte as *one unit* without transforming 8-bit information.
OR is it possible to set/reset some flags on the standard 1200-bps modems
to accomplish the object ?

   thanks. in advance.

kyongsok kim

dept. of computer science; univ. of illinois at urbana-champaign

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