Hi my friends.. I have some trouble with my project. I try to communication microcontroller AT89C51 with computers. I didn't use rs 232, but I replacement with NOT gates. sometimes run and sometimes not run, I don't know why???? mybe you have idea???
i think he dont use MAX232 or IC RS-232 converter. Like this http://microengineeringlabs.com/resources/pbpmanual/5_61-5_64.htm
"i think he dont use MAX232 or IC RS-232 converter." There's no "think" about it: he specifically stated that he didn't - and the results are just what is to be expected! He is reaping the benefits of his folly. Note that the web page you cited says, "... allow most applications to run without level converters" (my emphasis). If you want something that you know will work, rather than just hoping that "most" of the time is good enough, you must use a proper RS232 transceiver. As that page also says, "... single-chip RS-232 level converters are common and inexpensive ..."
once more: The question: "I am not doing it right, why does it not work" does not make any sense. Erik
Whenever I use the bathroom, I make a terrible mess. I am not opening the toilet lid, instead am just leaving it down. What's wrong? Why does it always make mess?