From fdc@columbia.edu Sat Oct 19 06:27:27 2002 Flags: 000000000001 Return-Path: Received: from watsol.cc.columbia.edu (localhost [127.0.0.1]) by watsol.cc.columbia.edu (8.12.3/8.12.3) with ESMTP id g9JFRQq5008010 for ; Sat, 19 Oct 2002 11:27:26 -0400 (EDT) Received: by watsol.cc.columbia.edu (8.12.3/8.12.3/Submit) id g9JFRQoM008009 for fdc; Sat, 19 Oct 2002 11:27:26 -0400 (EDT) Path: newsmaster.cc.columbia.edu!phl-feed.news.verio.net!iad-feed.news.verio.net!iad-peer.news.verio.net!news.verio.net!news.maxwell.syr.edu!wn11feed!worldnet.att.net!bgtnsc05-news.ops.worldnet.att.net.POSTED!not-for-mail Message-ID: <3DB1547F.410E0CB@yahoo.com> From: CBFalconer Reply-To: cbfalconer@worldnet.att.net Organization: Ched Research X-Mailer: Mozilla 4.75 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.embedded Subject: Re: HDLC CRC Calculation References: <3daf2442.670703@news.saix.net> Content-Transfer-Encoding: 7bit Lines: 22 Date: Sat, 19 Oct 2002 14:09:33 GMT NNTP-Posting-Host: 12.90.172.183 X-Complaints-To: abuse@worldnet.att.net X-Trace: bgtnsc05-news.ops.worldnet.att.net 1035036573 12.90.172.183 (Sat, 19 Oct 2002 14:09:33 GMT) NNTP-Posting-Date: Sat, 19 Oct 2002 14:09:33 GMT Xref: newsmaster.cc.columbia.edu comp.arch.embedded:139330 Content-Type: text/plain; charset=us-ascii To: undisclosed-recipients:; Anton Erasmus wrote: > > On all the Serial Controllers I have used that supports HDLC, > there are 2 options for the standard HDLC CRC Calculation, namely: > Preset CRC with all 0s or all 1s. From a technical point of view > there does not seem to be any advantage in using the one over the > other. Is there any sort of preference in the various protocols > based on HDLC for either the one or the other option ? If the CRC is preset to 1's, input of a series of 0's will change it. That means you will always detect a too short, or too long, stream of 0's. If you preset to 0, things will not change with each zero byte input. If the input stream ends with its own CRC, in the correct byte order, the end result will be 0, which is a handy final check mechanism. -- Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net) Available for consulting/temporary embedded and systems. USE worldnet address!