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04/21/10 13:59
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 		 #175217 - External Interrupt on both Falling edge & rising edge
Hello forum,

i am using AT89S52 in a dimmer project and iam using a ZCD directly from mains without isolation. The 230V Mains hot side is connected thru a 1Meg resistor to the external interrupt pin P3.3 and neutral is connected to circuit Gnd thru another 1Meg resistor. i got this from an AVR application note and thought i could use this on 8051 which too has internal clamp diodes on I/o pins.

the above setup results in a square wave on ext.int pin, now the problem is normal 8051/2 like 89S52 can be configured to respond to falling edge of a signal and not to rising edge.

how can i cause interrupt on both the edges of the square wave signal ?

need help on this,

Regards,

Arun

List of 86 messages in thread
TopicAuthorDate
External Interrupt on both Falling edge & rising edge            01/01/70 00:00      
   ABORT!, ABORT!, ABORT!            01/01/70 00:00      
      Better circuits exists            01/01/70 00:00      
      one more            01/01/70 00:00      
   DANGER!! Don't Try This At Home!            01/01/70 00:00      
      Its not just Atmel            01/01/70 00:00      
   interrupts on both edges            01/01/70 00:00      
      Thank you All            01/01/70 00:00      
         Read about external Gate for Timer            01/01/70 00:00      
            gate for timer            01/01/70 00:00      
               Jan, will you Shhhhh!!!            01/01/70 00:00      
               Great Idea !            01/01/70 00:00      
                  But i've used up INT0 and INT1 pins            01/01/70 00:00      
                     int0 is gate for timer0            01/01/70 00:00      
                     T1(T0) pin is not use here            01/01/70 00:00      
                        so only one Ext.int pin will do            01/01/70 00:00      
                           i think so            01/01/70 00:00      
                              I haven't tried it yet            01/01/70 00:00      
                                 is a Zener that costly?            01/01/70 00:00      
                                 so try something safely            01/01/70 00:00      
                                    That the most exhaustive reply i got so far !            01/01/70 00:00      
                                       You are wellcome            01/01/70 00:00      
                                          Here's what i have done            01/01/70 00:00      
                                             simulation is partial            01/01/70 00:00      
                                                I'll try writing a sample code            01/01/70 00:00      
                                                   Dimmer            01/01/70 00:00      
                                                      its a dimmer for commercial sale            01/01/70 00:00      
                                                         Dimmer            01/01/70 00:00      
   Its in my Profile            01/01/70 00:00      
      is 8051/2 I/O similar to Zilog Z8            01/01/70 00:00      
         Cease and Desist            01/01/70 00:00      
         It's DANGEROUS - It's not about the IOs!!            01/01/70 00:00      
         Either you are NOT listening...or you don't want to listen            01/01/70 00:00      
            It's worse than that!            01/01/70 00:00      
               Its like openning Pandora's box            01/01/70 00:00      
                  chip A != chip B != chip C            01/01/70 00:00      
                  Consider these points...            01/01/70 00:00      
                     not a newbie to electronics            01/01/70 00:00      
                        What results do you really get from an experiment?            01/01/70 00:00      
                        Reply to Arun Kumar V            01/01/70 00:00      
                  what if the result is death?            01/01/70 00:00      
                     very positive opinion            01/01/70 00:00      
                     Thanks for the pointer            01/01/70 00:00      
   A generic approach to dual edge detection            01/01/70 00:00      
      Here is the method I have been using...            01/01/70 00:00      
      Oh Noes!!!!!!            01/01/70 00:00      
      4 -> 10 nsec Pulse Does Not Work for MCU            01/01/70 00:00      
         No additional logic gates            01/01/70 00:00      
         Modifying design            01/01/70 00:00      
            Yeah But...            01/01/70 00:00      
               If you say so            01/01/70 00:00      
                  Poppycock            01/01/70 00:00      
   Why you should not do this...            01/01/70 00:00      
      Galvanic isolation            01/01/70 00:00      
         Can't we use single AC optocoupler            01/01/70 00:00      
            not 1,8V            01/01/70 00:00      
            can be wrong circuit below            01/01/70 00:00      
               Critical again...            01/01/70 00:00      
                  varistor?            01/01/70 00:00      
                     Yes, but...            01/01/70 00:00      
            You can do a lot of things...            01/01/70 00:00      
               25V is too coarse            01/01/70 00:00      
                  use tha appnote I gave you the link to            01/01/70 00:00      
                  25V is not bad            01/01/70 00:00      
                     You still don't know what my product is?            01/01/70 00:00      
                        sorry            01/01/70 00:00      
                           Its O.K - this thread has crossed 65 replies            01/01/70 00:00      
                              npn            01/01/70 00:00      
                        no, I do not know what your product is            01/01/70 00:00      
                           Answers            01/01/70 00:00      
                              OK, then            01/01/70 00:00      
                                 No headphones            01/01/70 00:00      
                  Then take a better opto!            01/01/70 00:00      
                     he wants to build a Yogo, not a Mercedes            01/01/70 00:00      
                        which makes the lamp flicker when the fridge turns-off            01/01/70 00:00      
                           it (probably) does that anyhow            01/01/70 00:00      
                              No body wants to buy a Mercedez            01/01/70 00:00      
                                 What do you expect??            01/01/70 00:00      
                                    What is there to be ashamed of ?            01/01/70 00:00      
                                       Thread began with ....            01/01/70 00:00      
                                          Dead Horse is Alive and Kicking            01/01/70 00:00      
                                             obviously a comparator is a better solution            01/01/70 00:00      
                                                Oh My God...you having sleepless nights???            01/01/70 00:00      
                                             Then share it with us...            01/01/70 00:00      
                                             to Arun PLEASE get ...            01/01/70 00:00      
                                 what did you expect            01/01/70 00:00      

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