Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!nrl-cmf!ames!ubvax!versatc!mips!prls!philabs!micomvax!vo
From: vo@micomvax.UUCP (Vladimir Orlt)
Newsgroups: comp.sys.ibm.pc
Subject: Re: What is the difference between XT and AT serial ports
Message-ID: <1394@micomvax.UUCP>
Date: 29 Nov 88 16:56:31 GMT
References: <3078@dalcs.UUCP> <1232@unccvax.UUCP>
Reply-To: vo@micomvax.UUCP (Vladimir Orlt)
Organization: Philips Electronics Ltd. (TDS - Montreal) St. Laurent QC, Canada
Lines: 17

In article <1232@unccvax.UUCP> mru@unccvax.UUCP (Markus Ruppel) writes:
>From the National Semiconductor data sheet:
>
>	"The NS16450 is an improved specification version of the INS8250A
>	 Asynchronous Communications Element (ACE). The improved specifica-
>	 tions ensure compatibility with the NS32016 and other state-of-the
>	 -art CPUs. Functionally, the NS16450 is equivalent to the INS8250A."
>	 (typos mine...:-))

There is a difference between the NS16450 and the 8250 (I don't know the
difference between the 8250 and the 8250A); the 16450 interrupt line remains
active until all of the UART's pending/active interrupts are serviced (by 
reading the status register), whereas the 8250's interrupt line strobes after
each of these interrupts is cleared.

					Vlad the re-mailer
					...!philabs!micomvax