Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site fortune.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!fortune!yamauchi From: yamauchi@fortune.UUCP (Alan Yamauchi) Newsgroups: net.arch Subject: Re: Multi-valued logic Message-ID: <5067@fortune.UUCP> Date: Fri, 1-Mar-85 13:01:35 EST Article-I.D.: fortune.5067 Posted: Fri Mar 1 13:01:35 1985 Date-Received: Sat, 2-Mar-85 04:43:46 EST References: <1384@ut-ngp.UUCP> Reply-To: yamauchi@fortune.UUCP (Alan yamauchi) Organization: Fortune Systems, Redwood City, CA Lines: 28 Keywords: Voltage multiplexed pins In article <1384@ut-ngp.UUCP> vomlehn@ut-ngp.UUCP (vomlehn) writes: > >One application of multi-valued logic which I have never heard of is voltage- >multiplexing pins. . . . Some chip makers time-multiplexed pins, so that the >same set of pins may have address information during one time interval and >data information during the next. If the pins were voltage-multiplexed >a given pin would only contain data, but it would contain the data for two >logical data lines. Voltage multiplexed pins are already being implemented at some of the semi- conductor houses now, although not quite in the manner you suggested. This is done strictly for in house test purposes and mostly with the more complex parts such as uComputers and uProcessors. Applying voltages > 7V to certain pins on these parts allows the testers to dump either internal masked ROM or uCode. I'm not sure of exact voltage levels necessary to change the functionality of pins, but some other semi houses use an alternate method of dumping ROM or uCode, such as forcing certain opcodes in special sequences. Of course most of this in not common knowledge unless you've either worked in or are working in a semiconductor house. The technology to do what you suggest certainly exists, but to do it commercially in the bi-level logic world now would be quite costly. \ / Alan Yamauchi * \___/ UUCP: {ihnp4,ucbvax!amd,hpda,sri-unix,harpo}!fortune!yamauchi DDD: (415)594-2436 USPS: Fortune Systems Corp, 101 Twin Dolphin Drive, Redwood City, CA 94065