TTL COMPATABLE
From: ac937
Date: 07/30/89-09:32:33 AM Z
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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