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Latch and flip flop

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1 Latches and Flip-Flops Dr. Le Dung Faculty of Electronics and Telecommunications Hanoi University of Science and Technology Content •  Memory element •  Latches •  Flip-Flops Dr. Le Dung      2    Hanoi University of Science and Technology 2 A device with exactly two stable states Bistable multivibrator circuit Q1 on  Q2 off Q1 off  Q2 on 2 stable states as a memory element can store one bit Dr. Le Dung      3    Hanoi University of Science and Technology Memory element Latch Flip-Flop (with clock) 1-state or 0-state Q Q Excitation inputs 1-state (set): Q=1, Q=0 0-state (reset): Q=0, Q=1 Inhibited-state: Q = Q Set Reset Q Set Reset Q Clock Excitation inputs Dr. Le Dung      4    Hanoi University of Science and Technology 3 Latches •  SR latch (Set-Reset latch) + with NOR structure + with NAND structure •  Gated SR latch •  D latch (Delay or Data latch = transparent latch) •  Some applications of the latches (1) (2) (3) Dr. Le Dung      5    Hanoi University of Science and Technology Set-Reset Latch with NOR structure S R Q’ (next) 0 0 Q (latch)* 0 1 0 (reset) 1 0 1 (set) 1 1 Q’=Q’=0 (Inhibited) * Latch = No change SR latch S, R active “High” NOR structure Set Q=1,Q=0 Reset Q=0,Q=1 X Q=Q SR=10 SR=01 SR=00 SR=10 SR=00 SR=01 SR=11 SR=11 Inhibited State diagram (Moore) Latch Latch Dr. Le Dung      6    Hanoi University of Science and Technology 4 Set-Reset Latch with NAND structure S R Q’ (next) 0 0 Q’=Q’=1 (Inhibited) 0 1 1 (set) 1 0 0 (reset) 1 1 Q (latch)* * Latch = No change SR latch S, R active “Low” NAND structure Set Q=1,Q=0 Reset Q=0,Q=1 X Q=Q SR=01 SR=10 SR=11 SR=01 SR=11 SR=10 SR=00 SR=00 Inhibited State diagram (Moore) Latch Latch Dr. Le Dung      7    Hanoi University of Science and Technology SR latch timing diagram NOR SR Latch S, R active “High” Q’=Q’=0 (Inhibited) 1 1 1 (set) 0 1 0 (reset) 1 0 Q (latch)* 0 0 Q’ (next) R S (Illegal) Q’ = S + RQ Dr. Le Dung      8    Hanoi University of Science and Technology 5 Gated SR Latch * Hold = No action Gated SR latch E S R Q’ (next) 0 x x Q (hold)* 1 0 0 Q (latch) 1 0 1 0 (reset) 1 1 0 1 (set) 1 1 1 Inhibited E,S,R active “High” Set Q=1,Q=0 Reset Q=0,Q=1 X Q=Q ESR=110 ESR=101 0xx, 110 111 111 Inhibited State diagram (Moore) 0xx, 101 Dr. Le Dung      9    Hanoi University of Science and Technology D Latch E D Q’ (next) 0 x Q (hold)* 1 0 0 (reset=store 0) 1 1 1 (set=store 1) Set Q=1,Q=0 Reset Q=0,Q=1 ED=11 ED=10 0x, 11 0x, 10 Store 1 Store 0 Dr. Le Dung      10    Hanoi University of Science and Technology Data or Delay latch = transparent latch 6 Some applications of the latches (1) Dr. Le Dung      11    Hanoi University of Science and Technology (App 1) Debounce a mechanical switch Some applications of the latches (2) Dr. Le Dung      12    Hanoi University of Science and Technology (App 2) LED detect alarm system 7 Some applications of the latches (3) Dr. Le Dung      13    Hanoi University of Science and Technology (App 3) 74LS75 Quad D latch module with enable Flip-Flops •  Clock signals •  Clocked flip-flops + Master-Slave Flip-Flop (Pulse-triggered FF) + Edge-triggered Flip-Flop •  SR Flip-Flop •  JK Flip-Flop •  D Flip-Flop •  T Flip-Flop •  Asynchronous set and reset (Preset and Clear) •  Some applications of the flip-flops(1) (2) (3) Dr. Le Dung      14    Hanoi University of Science and Technology 8 Clock signals Dr. Le Dung      15    Hanoi University of Science and Technology Clocked Flip-Flops Dr. Le Dung      16    Hanoi University of Science and Technology 9 Master-Slave Flip-Flops Dr. Le Dung      17    Hanoi University of Science and Technology Edge-triggered Flip-Flops Dr. Le Dung      18    Hanoi University of Science and Technology PGT detector NGT detector 10 SR Flip-Flop (active with PGT) Dr. Le Dung      19    Hanoi University of Science and Technology SR Flip-Flop (active with NGT) Dr. Le Dung      20    Hanoi University of Science and Technology [...]... Pulse-triggered JK Flip- Flop Dr Le Dung      25    Hanoi University of Science and Technology D Flip- Flop Dr Le Dung      26    Hanoi University of Science and Technology 13 Make D Flip- Flop from JK Flip- Flop Dr Le Dung      27    Hanoi University of Science and Technology T Flip- Flop (active with NGT) Dr Le Dung      28    Hanoi University of Science and Technology 14 Clocked T Flip- Flop Dr Le Dung      29...JK Flip- Flop Dr Le Dung      21    Hanoi University of Science and Technology JK Flip- Flop (active with PGT) Dr Le Dung      22    Hanoi University of Science and Technology 11 JK Flip- Flop (active with NGT) Dr Le Dung      23    Hanoi University of Science and Technology Internal Circuitry of JK Flip- Flop Feedback Feedback Dr Le Dung      24    Hanoi University of Science and Technology... Science and Technology Asynchronous set and reset (1) Dr Le Dung      30    Hanoi University of Science and Technology 15 Asynchronous set and reset (2) JK-FF with Preset and Clear inputs Dr Le Dung      31    Hanoi University of Science and Technology Asynchronous set and reset (3) Dr Le Dung      32    Hanoi University of Science and Technology 16 Asynchronous set and reset (4) T-FF with Preset and Clear... of Science and Technology Applications of the Flip- Flop + Thiết kế các bộ đếm (Counter) + Thiết kế thanh ghi dịch (Shift register) + Thiết kế mạch dãy + Các ứng dụng khác Dr Le Dung      34    Hanoi University of Science and Technology 17 Some applications of the Flip- Flop (1) 3 bits Up-Counter Dr Le Dung      35    Hanoi University of Science and Technology Some applications of the Flip- Flop (2) Serial... Flip- Flop (1) 3 bits Up-Counter Dr Le Dung      35    Hanoi University of Science and Technology Some applications of the Flip- Flop (2) Serial shift register Dr Le Dung      36    Hanoi University of Science and Technology 18 . Edge-triggered Flip- Flop •  SR Flip- Flop •  JK Flip- Flop •  D Flip- Flop •  T Flip- Flop •  Asynchronous set and reset (Preset and Clear) •  Some applications of the flip- flops(1) (2) (3) Dr. Le. Science and Technology (App 3) 74LS75 Quad D latch module with enable Flip- Flops •  Clock signals •  Clocked flip- flops + Master-Slave Flip- Flop (Pulse-triggered FF) + Edge-triggered Flip- Flop. 1 Latches and Flip- Flops Dr. Le Dung Faculty of Electronics and Telecommunications Hanoi University of Science and Technology Content •  Memory element •  Latches •  Flip- Flops Dr.

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