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Jez Smith
04/03/10 00:39
Modified:
  04/03/10 01:08

Read: 497 times
Birmingham
England


 
#174801 - Reset
Responding to: ???'s previous message
This and some other examples I have found tend to connect the reset pin of the MCU to a capacitor toward the Vcc and a resistor toward ground. Why is this? when this pin is high for 2 cycles the chip resets right? why is this needed here?
The 8052 is reset at power on by holding the reset pin low after power on which does two things,three even,it allows the power supply to settle and it allows the crystal oscillator to start up and the internal registers to go to a known state. Using the capacitor/resitor is a very unreliable method used in early designs which has now been superceeded by the use of a power on reset supervisor which will perform the reset correctly and will reset the processor when the power supply goes below a set level.
A search on here will reveal long and detailed discussions about such devices.

List of 24 messages in thread
TopicAuthorDate
New with MCUs need a little help.      Rickey Ward      04/02/10 14:43      
   Hi      Jez Smith      04/02/10 15:30      
      Some answers but now concerns      Rickey Ward      04/02/10 21:36      
         Normally very weak source      Per Westermark      04/02/10 21:41      
            Can't find that detail      Rickey Ward      04/02/10 21:55      
               Not many 805x's have push-pull outputs.      Richard Erlacher      04/02/10 22:21      
         Reset      Jez Smith      04/03/10 00:39      
         SDCC      Jez Smith      04/03/10 00:42      
   Books      Andy Neil      04/03/10 05:02      
   Electronics      Andy Neil      04/03/10 05:05      
   first read "the bible"      Erik Malund      04/03/10 05:56      
      Maybe not First?      Andy Neil      04/03/10 06:09      
         Rickey?      Erik Malund      04/03/10 06:21      
            I am new, Just somthing I wanted to do.      Rickey Ward      04/03/10 10:46      
      Dead links      Rickey Ward      04/03/10 10:50      
         No you are right      Jez Smith      04/03/10 12:47      
            hrm      Rickey Ward      04/03/10 14:32      
               Argh!!!      Jez Smith      04/03/10 14:39      
               It's a highly dynamical thing...      Kai Klaas      04/03/10 15:05      
                  a reset writeup, but you don't want to read it now      Jan Waclawek      04/03/10 15:53      
                     You mean this one?      Kai Klaas      04/03/10 19:52      
                        Thanks      Rickey Ward      04/03/10 22:16      
         not dead, just incorrectly copied      Jan Waclawek      04/03/10 13:56      
            Thanks      Rickey Ward      04/03/10 14:32      

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