VLSI implementation of adders

Replies

• 

  Nayan Goenka

  I studied BCD adders too in the topic of Adders and I guess you are missing that. If you are including all adders, then BCD can also be included. I am not sure about its speed constraint though.
• 

  Kaustubh Katdare

  Thread Moved to Electronics engineering section.
• 

  Teresan

  Hi, I am not including BCD adders. Am selective in choosing the HSA (high speed adders) I chose only carry select,save and skip and concluded that carry select has the good speed capability..
  I just wanna know about others...
  I ll find out the speed capability of BCD adder too..
• 

  Cyborg 009

  Kogge-Stone adder...fastest adder design possible.
  Manchester carry chain...
• 

  Teresan

  Cyborg 009

  Kogge-Stone adder...fastest adder design possible.
  Manchester carry chain...

  Thank you ..
  Can you explain what is Kogge stone adder is ?
  And how it works?
• 

  Cyborg 009

  variation of carry look ahead...
  expansion for 4bit kogge stone..
  Si= Pi XOR Ci-1
  S0 = (A0 XOR B0) XOR Cin
  S1 = (A1 XOR B1) XOR (A0 AND B0)
  S2 = (A2 XOR B2) XOR (((A1 XOR B1) AND (A0 AND B0)) OR (A1 AND B1))
  S3 = (A3 XOR B3) XOR ((((A2 XOR B2) AND (A1 XOR B1)) AND (A0 AND B0)) OR (((A2 XOR B2) AND (A1 AND B1)) OR (A2 AND B2)))
  S4 = ((((A3 XOR B3) AND (A2 XOR B2)) AND (A1 AND B1)) OR (((A3 XOR B3) AND (A2 AND B2)) OR (A3 AND B3)))
• 

  Teresan

  Cyborg 009

  variation of carry look ahead...
  expansion for 4bit kogge stone..
  Si= Pi XOR Ci-1
  S0 = (A0 XOR B0) XOR Cin
  S1 = (A1 XOR B1) XOR (A0 AND B0)
  S2 = (A2 XOR B2) XOR (((A1 XOR B1) AND (A0 AND B0)) OR (A1 AND B1))
  S3 = (A3 XOR B3) XOR ((((A2 XOR B2) AND (A1 XOR B1)) AND (A0 AND B0)) OR (((A2 XOR B2) AND (A1 AND B1)) OR (A2 AND B2)))
  S4 = ((((A3 XOR B3) AND (A2 XOR B2)) AND (A1 AND B1)) OR (((A3 XOR B3) AND (A2 AND B2)) OR (A3 AND B3)))

  Yeah i get it 😀
  Thanks alot.. I will include it in my project..
• 

  Nayan Goenka

  Cyborg 009

  Kogge-Stone adder...fastest adder design possible.
  Manchester carry chain...

  
  That really seems a good example. do you happen to have any link or diagram of this type of adder? That will help understand the algorithm. The ANDs and ORs might be a bit confusing. you can also give an image from your notebook if you happen to have drawn any.
• 

  Jeffrey Arulraj

  Nayan Goenka

  I studied BCD adders too in the topic of Adders and I guess you are missing that. If you are including all adders, then BCD can also be included. I am not sure about its speed constraint though.

  BCD adders can be implemented using existing high speed adders and they just need another stage to compensate and balance the answer
• 

  Cyborg 009

  Nayan Goenka

  That really seems a good example. do you happen to have any link or diagram of this type of adder? That will help understand the algorithm. The ANDs and ORs might be a bit confusing. you can also give an image from your notebook if you happen to have drawn any.

  
• 

  kheerthi chandru

  Cyborg 009

  Kogge-Stone adder...fastest adder design possible.
  Manchester carry chain...

  
  can u explain about Manchester carry chain ?
• 

  Jeffrey Arulraj

  kheerthi chandru

  can u explain about Manchester carry chain ?

  #-Link-Snipped-#
  
  This tells us in detail about the carry chain adders Do read the article and post your queries here
• 

  kheerthi chandru

  i need coding fr carry skip adder. if any1 can search for it please post it as soon as possible. little urgent
• 

  Jeffrey Arulraj

  kheerthi chandru

  i need coding fr carry skip adder. if any1 can search for it please post it as soon as possible. little urgent

  Are you looking for the VHDL program of that adder or any other language
  
  Be more specific that will help us in helping you better
• 

  Jeffrey Arulraj

  
  G(0) := a(0) and b(0);
  P(0) := a(0) or b(0);
  C(1) := G(0) or (P(0) and cin);
  for i in 1 to R-1 loop
  G(i) := a(i) and b(i);
  P(i) := a(i) or b(i);
  C(i+1) := G(i) or(P(i) and C(i));
  end loop;
  

  This is one way of getting it done
  
  Do execute it and tell us the result