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Michael Karas
01/02/12 03:56
Read: 561 times
Beaverton Or
USA


 
#185248 - Your Reset Input
Responding to: ???'s previous message
Adam Collins said:
Can u ellaborate? I looked at the application notes of atmel it says the reset is active low. While in at89s52 rst is active high. Do u mean I should put an inverter? I am using stk500 plugin in avr studio 4. Thanks for your response!


The reset is active high on this part and that is the main point of my comment. If you are willing to accept the use of the crappy resistor / capacitor type (R/C) reset timing circuit then for a high true reset the normal circuit configuration is to put a resistor to GND from the RST pin and capacitor to VCC from the RST pin. I've seen folks use 1uF cap and 47K resistor for this type of reset circuit. My general recommendation though is to not use an R/C reset circuit and use a suitably selected reset generator type chip.

When you try to activate the ISP mode do check that the RST pin is held high from VCC on and kept there by the programming device. Also check to make sure that your XTAL1 and XTAL2 pins are actively oscillating just after the VCC comes on. ISP with this part will not work unless both these conditions are met.

Michael Karas


List of 32 messages in thread
TopicAuthorDate
AT89S52 and ISP problem      Adam Collins      01/01/12 13:38      
   Quick Schematic Obversation      Michael Karas      01/01/12 18:28      
      hmm      Adam Collins      01/01/12 22:20      
         Your Reset Input      Michael Karas      01/02/12 03:56      
            Thanks!!      Adam Collins      01/02/12 07:28      
   Your schematic is wrong      David Prentice      01/02/12 03:35      
   The AT89S52 needs a reset chip!      Kai Klaas      01/02/12 05:44      
      The AVRISP-2 is a USB device      David Prentice      01/02/12 06:02      
   what an AWFUL design      Erik Malund      01/02/12 07:35      
      Isn't mine!      Adam Collins      01/02/12 08:06      
         Compare several schematics      David Prentice      01/02/12 08:16      
            Thanks!!      Adam Collins      01/02/12 08:41      
               Sink or source? Does matter a lot!      Per Westermark      01/02/12 08:50      
                  Not granted      Adam Collins      01/02/12 09:07      
                     Processor can be used      Per Westermark      01/02/12 09:20      
                        Yeah..      Adam Collins      01/02/12 09:33      
                     cure for ignorance      Erik Malund      01/02/12 11:11      
         you forgot the quotes      Erik Malund      01/02/12 08:23      
         well      Erik Malund      01/02/12 08:30      
            Funny      Adam Collins      01/02/12 08:47      
               RC resets are evul      Per Westermark      01/02/12 08:57      
                  So?      Adam Collins      01/02/12 09:02      
                     Not necessarily,,,      Kai Klaas      01/02/12 09:18      
                     I guess you are a student / hobbyist      David Prentice      01/02/12 09:19      
                        Oh..      Adam Collins      01/02/12 09:30      
                        Even or better just then...      Kai Klaas      01/02/12 09:45      
                           Where to apply 100nF?      Adam Collins      01/02/12 10:01      
                              Shortest possible distance      Per Westermark      01/02/12 10:34      
                        especially not for a hobbyist      Erik Malund      01/02/12 11:23      
                  RC RESET worked fine for years ,,, but ...      Richard Erlacher      01/02/12 20:01      
               no, not "will" but "is likely to"      Erik Malund      01/02/12 11:17      
                  an added IMPORTANT comment      Erik Malund      01/02/12 11:26      

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