Digital Design Session 21
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The document focuses on the applications of D flip-flops, specifically in creating frequency dividers, 4-bit asynchronous up counters, and down counters. It includes example circuits and quizzes to assess understanding of these concepts. The material presents a clear overview of how D flip-flops can be used in digital design.
Digital Design Session 21
- 1. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com
- 2. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 2 Session 21: Focus Applications using D Flip-flop ◦ Frequency Divider ◦ 4-bit Asynchronous Up counter ◦ 4-bit Asynchronous Down counter
- 3. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com Applications using D-Flip-flops
- 4. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 4 Quiz 1: What does this circuit do? 4-bit Data storage
- 5. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 5 Quiz 2: What does this do? fout = fin /2 Note: 74LS74 is a Dual D-type Positive Edge Triggered fin fin / 2 = fout Positive Edge Triggered D Flip-flop Initially Q (fout) is Zero fout
- 6. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 6 Example 1: 4-bit Asynchronous Up Counter It counts the clock pulses from 0000 to 1111 Q’ of previous stage is fed as clock to the next stage flip-flop Since the transitions of flip-flops are not happening based on the same clock pulse, this is an asynchronous counter All are +ve edge triggered D flip-flops Initially all D Flip-flops are cleared Q3Q2Q1Q0 = 0000 CLK is clock input CLK Q0 Q1 Q2 Q3 FF0 FF1 FF2 FF3 CLK
- 7. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 7 Example 2: 4-bit Asynchronous Down Counter Initially all D Flip- flops are set to 1111 It down counts the clock pulses from 1111 to 0000 CLK CLK Q0 Q1 Q2 Q3
- 8. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 8 Session 21: Summary Applications using D Flip-flop ◦ Frequency Divider ◦ 4-bit Asynchronous Up counter ◦ 4-bit Asynchronous Down counter
- 9. Digital Design – © 2020 Mouli Sankaran Email: mouli.sankaran@yahoo.com 9 References Ref 1 Ref 2