The thread to discuss DIGITAL CIRCUITS questions

Replies

• 

  narayana murthy

  cranky

  Hey,
  This is yet another attempt to revive discussions on Digital and RC circuits especially for placements in TI,Qualcomm etc.Please do contribute in the discussion.Do number your questions.
  Q1:How to solve problems that involve designing a counter with frequency/2,f/3 etc.

  using cyclo converters lol
• 

  hexreader

  cranky

  Q1:How to solve problems that involve designing a counter with frequency/2,f/3 etc.

  74HC4059? #-Link-Snipped-#
  CD4526? CD4526 Datasheet
  
  Maybe if you could be more specific with your question........
  What sort of divide values had you in mind? Any particular technology, or other requirements?
  
  Are you looking for logic circuits, or a ready built unit with LED/LCD readout?
• 

  cranky

  @narayanamurthy: 😛
  @hex:meant like given a clock with duty cycle of 1/2..obtain 1/8 or 1/3 etc.(using jk flip flops)
• 

  hexreader

  cranky

  @hex:meant like given a clock with duty cycle of 1/2..obtain 1/8 or 1/3 etc.(using jk flip flops)

  All those kinds of circuit can be found on Google. Something like this maybe? #-Link-Snipped-#
• 

  narayana murthy

  hey friends cool please don't use links in the threads like these it is just for share of our concepts
  am i right cranky
• 

  hexreader

  narayana murthy

  hey friends cool please don't use links in the threads like these it is just for share of our concepts
  am i right cranky

  I do not understand. Should I explain how to make a "divide by n" circuit purely in words?
  
  The links I provided seemed highly appropriate to my understanding. I do not see how I could answer the question without reference to diagrams?
  
  Please explain what I did wrong and what the correct response should be.
  
  Presumably I can delete all of my posts if it helps
• 

  narayana murthy

  hexreader

  I do not understand. Should I explain how to make a "divide by n" circuit purely in words?
  
  The links I provided seemed highly appropriate to my understanding. I do not see how I could answer the question without reference to diagrams?
  
  Please explain what I did wrong and what the correct response should be.
  
  Presumably I can delete all of my posts if it helps

  hey sorry if i am hurt you i just said about the pattern i am not pointing you i think you don't about these question and answer thread actually in threads like this we also know about answer but ask questions to get more knowledge note that he is not seeing for help if he asks help never mind whats you give as answer but it is not case here
• 

  hexreader

  narayana murthy

  hey sorry if i am hurt you

  No need for apology, no hurt caused, and I thank you for explaining.
  
  I am used to other forums, which mainly focus on specific problem solving. I guess this forum is a little more general.
  
  I think I understand now, and I failed to spot the word "discussion" in the OPs first post.
  
  I have ruined the flow of the thread now, for which I apologise. Please feel free to start a new one.
  
  Guess it is very obvious that I am a newbie here 😀
• 

  hexreader

  cranky

  Hey,
  Q1:How to solve problems that involve designing a counter with frequency/2,f/3 etc.

  I would use (say) four JK flip flops to count 0 to 15. Let's say the four outputs are A B C D.
  
  Next connect each JK output to one input of a 2 input XOR gate. Connect the other XOR input to '1' or '0' depending on what divisor value you want. Let's call these four "other" inputs W X Y Z.
  
  You then connect the four XOR outputs to a 4-input AND (or more likely NAND) gate.
  
  Connect the output of the AND gate to the clear pin of all JK flip/flops (or if clear is active low, use a NAND gate).
  
  The four XOR gates act as a "compare" circuit, then if all four "compares" are true, the NAND gate will reset the counter.
  
  So the counter will keep counting up until ABCD matches WXYZ, then will reset to zero.
  
  WXYZ is effective the binary value of 'n' to make a "divide by n" counter, where n is selectable from 1 to 15.
  EDIT: Correction: This more likely makes a "divide by n+1" counter, depending on the exact circuitry and flip/flop type.
  
  Hope this helps.
• 

  everett.pattison

  A very simple way to create a divide-by-2 counter is to use a JK flip flop with the J and K pins tied together to your frequency input. The flip flop acts as a "toggle" in this mode. On every rising (or falling depending on the IC) edge of the input the output changes to the opposite state. Because of this it acts as though the frequency is being divided by 2 and only change state once per period as opposed to 2.
  
  On a side note, this toggle is a great way to get exactly a %50 duty cycle, the only downfall is it halves the frequency.
• 

  cranky

  @pattinson,hex,narayan:thanks.could some one post any question @__@
• 

  cranky

  Q2:Give a generalised expression for finding the number of flip flops for counting any sequence:Ex:11,19,7,1119,11,19,7,1119 etc.
• 

  Adivy

  I guess before counting any sequence we have to detect the sequence which can be done using a sequence detector along with which we can use a counter to count no. of times the sequence is detected.About generalised expression ,I dont know any expression as such but we can get number flip flops(FFs) as soon as we get the states used in the Detector that is if there are 2^n states we have n FFs.
  
  If I am wrong please correct me.