Date: Wed, 7 Jul 1999 12:44:06 -0700 From: "David Schwartz" <davids@webmaster.com> To: "John Hay" <jhay@mikom.csir.co.za> Cc: <stable@FreeBSD.ORG> Subject: RE: PPS API change assert/clear Message-ID: <000401bec8b1$12fba1c0$021d85d1@youwant.to> In-Reply-To: <199907071936.VAA06015@zibbi.mikom.csir.co.za>
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> Do you mean that if you measure the voltage on the DCD pin and it go from > negative to positive (ASSERT) you get a CLEAR from the software? Negative to positive is not an assertion of DCD. DCD is active low. It has been logically asserted when the voltage goes negative. > That is > wrong and not what I see here. Do you have version 1.224.2.6 of sio.c? > I know it has been broken in versions before that in stable and versions > before 1.246 in current. Why is that wrong? (I know, the standard says so, but it seems to me that the standard makes no sense.) When I asked Ulrich Windl, one of the authors of the standard, (but this may be before the clarification), he said: Me: Since DCD is active-low, is an 'ASSERT' a high-to-low transition on the DCD pin? Ulrich: This problem has been discussed a lot. ASSERT is from the perspective of the UART's register. ASSERT means the CD bit in the modem status register has been set. Depending what your line drivers and level converters do, the level may change. Ulrich gave me the answer that I expected. The one that I thought made sense. And the Linux PPSkit that Ulrich Windl wrote works as he stated. It's hard for me to keep my software working when the definition keeps changing. :/ David Schwartz http://www.gpsclock.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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