7.10.2 D Flip-Flop

Chapter 7.10.2 D Flip-Flop

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 7. DIGITAL CIRCUITS150SRQQ00undefined0110100111no changeRS flip-flopNQQNRNSNSNRQNQFigure 7.19: The RS flip-flop constructed from NAND gates, and its circuit symbol andtruth table.SCRCCQQxx0no change001no change0110110110111undefined00pno change01p0110p1011pundefinedRcCScSRQNQScRcCQNQFigure 7.20: The clocked RS flip-flop can be constructed from an RS flip-flop and twoadditional gates, the schematic symbol for the static clocked RSFF and its truth table.7.10.2D Flip-FlopThe D flip-flop avoids the undefined states in the RSFF truth table by reducing the numberof input options (figure 7.21).DCQQx0no change0p011p10CDScRcCQNQDCQNQFigure 7.21: Statically triggered D flip-flop (transparent latch) mechanized with clocked RS,and the schematic symbol and its truth table.The statically clocked DFF is also known as a transparent latch.7.10.3JK Flip-FlopThe JKFF simplifies the RSFF truth table but keeps two inputs (figure 7.22). The togglestate is useful in counting circuits. If the C pulse is too long this state is undefined andhence the JKFF can only be used with rigidly defined short clock pulses.