TTL COMPATABLEFrom: ac937
Date: 07/30/89-09:32:33 AM Z
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From: ac937 Subject: TTL COMPATABLE Date: Sun Jul 30 09:32:33 1989 WHAT DOES IT MEAN TTL.COMPATABLE. AND IS THE 8-BIT'S SIO PORT TTL COMPATABLE. I HAVE A DIAGRAM OF A TTL TO RS-232 INTERFACE I WOULD LIKE TO BUILD IF POSSABLE. ALL I GET WHEN I CALL ATARI IS THEY WELL CALL AND YET THEY HAVN'T. ANY HELP JOHN WILL BE GREAT FULL. AC-937 RICH ** Answered by JOHN SUCHY (aa271) on Sun Oct 25 03:35:40 1987 ** TTL is a particular family of computer chips whose major feature is the logical definition of "low" or "false" as between 0 and .4 volts, and of "high" or "true" as between 2.5 and 5.0 volts. "TTL compatible" means that -- in your case -- the part of the circuit that attaches directly to the computer shares these definitions. RS-232 defines high as 10 to 12 volts, and low as -10 to -12 volts. The TTL to RS-232 adapter basically converts voltage levels from one standard to the other. The Atati SIO port does use the TTL definitions of high and low. One word of caution, however: you must make some provision for selecting the Serial port as opposed to any other peripheral or you will be sending all disk drive and printer accesses out the port. I bought a product called "R-Verter" a few years ago that was supposed to work this way, but never could get it to function. Good luck and let us know if you get it going. Your Co-sysop John E. Suchy aa271
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