From owner-freebsd-stable Wed Jul 7 11:58:50 1999 Delivered-To: freebsd-stable@freebsd.org Received: from shell.webmaster.com (mail.webmaster.com [209.133.28.73]) by hub.freebsd.org (Postfix) with ESMTP id A3D3815473 for ; Wed, 7 Jul 1999 11:58:46 -0700 (PDT) (envelope-from davids@webmaster.com) Received: from whenever ([209.133.29.2]) by shell.webmaster.com (Post.Office MTA v3.5.3 release 223 ID# 0-12345L500S10000V35) with SMTP id com; Wed, 7 Jul 1999 11:58:44 -0700 From: "David Schwartz" To: "John Hay" Cc: Subject: RE: PPS API change assert/clear Date: Wed, 7 Jul 1999 11:58:44 -0700 Message-ID: <000f01bec8aa$bc9bb870$021d85d1@youwant.to> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook 8.5, Build 4.71.2377.0 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300 In-Reply-To: <000a01bec8a9$8237dd40$021d85d1@youwant.to> Importance: Normal Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Wow. It seems you're right. This still makes no sense to me, but it does seem to be the standard! When DCD is asserted, you will get a clear event. When DCD is cleared, you will get an assert event. Go figure: A PPS signal consists of a series of pulses, each with an ``asserted'' (logical true) phase, and a ``clear'' (logical false) phase. The two phases may be of different lengths. The API may capture an ``assert timestamp'' at the moment of the transition into the asserted phase, and a ``clear timestamp'' at the moment of the transition into the clear phase. The specific assignment of the logical values ``true'' and ``false'' with specific voltages of a PPS signal, if applicable, is outside the scope of this specification. However, these assignments SHOULD be consistent with applicable standards. Implementors of PPS sources SHOULD document these assignments. --------- Reminder to implementors of DCD-based PPS support: TTL and RS-232C (V.24/V.28) interfaces both define the "true" state as the one having the highest positive voltage. TTL defines a nominal absence of voltage as the "false" state, but RS-232C (V.24/V.28) defines the "false" state by the presence of a negative voltage. --------- DS > > > > > > It seems that the logic of assert and clear have changed. > > Now an assertion > > > of DCD is considered a clear, and vice-versa. Why was the > logic broken? > > > > > > > The PPSAPI draft was clarified and we were the odd ones out, so > we changed > > to be compatable to the rest. > > That makes no sense. I know Linux is currently the same way > FreeBSD was. > Can you send me a copy of this 'clarification'? > > I can't understand how this can possibly make sense. I now > get a 'CLEAR' > event whenever I assert DCD and an 'ASSERT' event whenever I clear DCD. > > DS To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message