Confusion over J-K and Master-Slave flip flops

Discussion in 'General Electronics Chat' started by hp1729, Nov 26, 2015.

  1. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    J-K flip flops are a bit more complicated than shown in other threads. Often simplified as a clocked S-R latch it doesn't explain all the operation of the J-K flip flop. Design 505 A, attached, shows a Clock latch (transparent latch). Design 505B shows a J-K positive edge triggered latch. Design 506 shows a J-K Master / Slave design. All are simplified and don't accurately represent any specific IC. "J" and "K" being the initials of the designer, John Kardash (according to legend),
     
    Hypatia's Protege likes this.
  2. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    Added note ...
    There isn't always consistency on any given J-K flip flop. A 747x may be a Master/Slave design but the 74LS7x version of the same chip may not be. Read data sheets carefully.

    Another note ...
    Jamming both asynchronous inputs (Set and Clear) at the same time can give interesting results also. On some (usually TTL) it will make both outputs go high. On CMOS J-Ks it will probably make both outputs go low.
    74LS76, both go high
    CD4027, both go low
    74HCT76, I don't remember. I don't think I've ever played with one.
     
    Hypatia's Protege likes this.
  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    2,781
    1,228
    Hadn't heard that one:confused: -- I do, however, recall "Jack Kilby" being rather 'popular' in the early 90's --- Considering the circuit (and nomenclature) dates from the late 1940's (when it was implemented with electron tubes) the "Kilby mythos" likewise fails the test of reason --- The truth likely relates to an effort on the part of developers to preclude confusion with the RS latch -- hence, 'borrowing' the coincidental alphabetic proximity of RS (i.e. Reset/Set), the world was given 'JK':cool::D -- Just my musings of course - Tho' I daresay same hold their own with the rest of the 'pack':D:D:D

    Sincere thanks for your informative posts!:):):)

    Best regards
    HP:)
     
    Last edited: Nov 26, 2015
  4. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    Did a search and came up with this ...
    (patent office)

    Oct. 14, 1969 1 J. J. KARDASH 3,473,053
    TWO-INPUT BISTABLE LOGIC CIRCUIT OF THE DELAY FLTFFLOP TYPE Filed July 11, 1966 INVENTOR JOHN J. KARDASH AGENT.
     
    AnalogKid and Hypatia's Protege like this.
  5. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    2,781
    1,228
    Thanks for your research/reply!:) It was my understanding that the circuit (bearing the moniker "JK flip-flop") dated from the 'ENIAC era' --- Another childhood illusion shattered!:(:D:cool: --- Seriously, it's nice to have the straight facts! - thank you!!!:)

    While questions are what these fora are 'all about' and always welcome -- I wish to commend you on your refreshing approach of posting facts of interest - I learned something today without so much as asking! -- A good thing!:)

    Very best regards
    HP:)
     
  6. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    :)
    And my wife says I'm only full of .... oh, never mind.
    :)
     
    Hypatia's Protege likes this.
  7. MrAl

    Well-Known Member

    Jun 17, 2014
    2,425
    490
    Hi,

    There was a patent that predates that one by some 10 years filed by a Dr. Nelson where he specifies J and K inputs, and the origin supposedly came from starting from using a double letter system to label all of the flip flops in his system like A and B, C and D, E and F, G and H, and then J and K (note the letter "i" is often skipped in electronic work nomenclature so that it can not be confused with the number 1 or the lower case letter "L", as is the letter "Q". But he realized that he would run out of letters in the large system so instead he decided to use J and K for all of them simply because they were not bothersome or would not be confused with other lettering systems (the quote uses the word "innocuous".
    This patent was applied for in 1953 and granted in 1958, which also predates the work of Jack Kilby at TI by about 5 years.
    So as far as i know, that's the earliest record of the use of the J K terminology.
     
    Hypatia's Protege likes this.
  8. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    Ah, the plot thickens!
    Interesting, thanks.
     
  9. Aleph(0)

    Member

    Mar 14, 2015
    343
    323
    HP Ha ha! What happened? You're supposed to be unbeatable at trivial pursuit:D! Now you better stop eyeing your radial arteries that way:eek: :D
     
  10. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    2,781
    1,228
    You're funny Aleph - but in all seriousness - inasmuch as discovering one's mistakes equates to garnering knowledge --it is nothing to be ashamed of!:):):)

    All the best
    HP:)
     
  11. MrAl

    Well-Known Member

    Jun 17, 2014
    2,425
    490
    Hi,

    Very well said :)

    I'd just like to note here that i am certainly not any kind of historian either, i just happen to know some things here and there. I hated history in grammar school, and only got interested a little recently maybe over the past 15 years or so. I found that many things happened in the past that are still interesting today and people like to tallk about stuff that happened in the past quite often, so i got a little interested after all. Some of the stuff that happened some 300 years ago and before that is almost too hard to believe.
     
    Hypatia's Protege likes this.
  12. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    I couldn't find a data sheet for a flip flop that uses "A" through "K" lettering terminology for pins. Any reference would be helpful. Certainly that alphabet has a big history.
     
  13. MrAl

    Well-Known Member

    Jun 17, 2014
    2,425
    490
    Hi again,

    Well no, the way i understood it was that he originally had a a LOT of flip flops that needed their inputs labeled, so he started using letters: A,B, and C,D, etc. So it was A and B for the first, C and D for the second, etc. But that means once we get up to Y and Z we run out of letters, so he decided to do them all the same, with just J and K and i suppose just let the IC number (IC1, IC2, etc., or U1, U2, etc.) show the individual flip flop packages.
    Also the way i understood it was that he chose J and K over the others because he did not want it to sound like lettering used for other flip flops or maybe even other purposes in electronics. For example, not R and not S, and certainly not Q.
     
  14. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
    1,948
    219
    I've been around since computers were made of transistors (Univac 1212) and don't remember that lettering on flip flops. Not that my memory serves me flawlessly these days. :)
     
  15. WBahn

    Moderator

    Mar 31, 2012
    17,726
    4,788
    I don't think anyone is saying that he used the earlier letters -- only that he originally intended to and, in the process, realized how impractical it was for anything beyond very simply systems and so adopted the J and K labels using subscripts to distinguish them.

    https://www.quora.com/What-does-J-K-in-J-K-flip-flops-the-electronic-circuit-mean-Who-named-it
     
Loading...