How to using a JK flip-flop to build a 7 segment display ?

is a good place to start.

-- _____ _ _ |_ _| | | | | | | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __ | | / _` | '_ ` _ \\ | __ |/ _ \\| '_ ` _ \\ / _ \\ '__| _| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ | |_____| \\__,_|_| |_| |_| |_| |_|\\___/|_| |_| |_|\\___|_| __ ____ / _| | _ \\ ___ | |_ | |_) | ___ _ __ __ _ / _ \\| _| | _ < / _ \\| '__/ _` | | (_) | | | |_) | (_) | | | (_| |_ \\___/|_| |____/ \\___/|_| \\__, (_) __/ | |___/

Are you really going to school some place where there are neither instructors nor teaching assistants who talk to students? That's the preferred route -- if for no other reason then if 1/4 the class asks the same question (and the guy's not a dip) he'll realize he's got to go over the material again.

This is a basic exercise in digital logic, although a 7-segment display is a bit much. If you truly are tasked with using seven flip-flops, you want to make a map of the ten allowable states of the display, with the J and K inputs necessary to each flip-flop to generate the next step in the count down. With four bits this is easily done by exhaustively listing all 16 possible states and their follow-ons, then making a Karnaugh map, but with seven it would be a pain. There's a technique that basically works like a Karnaugh map in tabular form, but I can't remember it, and you'd still need 128 entries just to get 10 valid states.

You _could_ look at the seven segments to see if there are just four or five unique ones, then use those for your Karnaugh map -- this might be how I would proceed, assuming I couldn't just use a PIC and some software.

If you're just supposed to use J-K flip-flops _somehow_ then I suggest you make a plain-jane 4-bit down counter, and a bunch of NAND gates to map the bits to the segments -- I suspect this will require less logic, but what do I know?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" came out in April.
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look at the timing diagram, or download a datasheet, you will see that for every two clock pulses going in, only one comes out.

Now what will happen when you feed the output from one FF to another?

If you repeat this you get a binary counter, add a bit of decoding hardware and drive your display

martin

The many questions like this that are posted here re-enforces my own opinion of most institutions of learning.

Luhan

schreef in bericht news: snipped-for-privacy@p79g2000cwp.googlegroups.com...

Good design starts with good specification. As long it's not clear for yourself what exactly you have to design you're in the mist. So what does it have to do and how should it look like?

petrus bitbyter

You are right there! Schools anymore are force feeding info, and don't really care to take the correct amount of time to let students really learn the basic foundation of a subject before moving on. And then the students don't want to appear brain dead and ask the questions, So they turn to places like here to ask. Students should never be alowed to move on, without a full understanding of basic circuits. It's like skipping the foundation of a house and go on building the walls, It makes a weak structure. JTT

Thank all... i will read as a referrence... i think i already got a little idea... if i got any question i will post here again...

Kuan Ming

Easy rule for JK flipflops: if J and K are different, then at the clock the Q-/Q output will match the inputs (J to Q, K to /Q). If J and K are both high, the outputs will toggle. If J and K are both low, the outputs will not change. All this assumes the R and S inputs are inactive.

Whenever I see post like that I marvel at the job-for-life + huge-salary opportunity that the standard level of education seems to be creating.

The downside is that the b*stard politicians will find a way to make me work well beyond 70 years to pay the subsistence of all the "students"!!

You have to do it using *only* JK flipflops or your teacher request you to build a counter with JK flipflops, a binary to bcd converter and one 7 seg display ?. Ask him again...

Vasile