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Sequential Circuits and Registers: Types and Applications

Learn about different types of sequential circuits, including registers and counters, and their applications in storing and processing data. Explore how to design sequential circuits using registers and ROMs. Additional readings provided.

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Sequential Circuits and Registers: Types and Applications

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  1. 7. Sequential circuits, 2nd part • Objectives: To recognize and know to use the principal types of sequential circuits • Registers • Counters • Generators of imposed sequences

  2. Registers • Are sequential circuit capable of storing information of several bits (word). • Made of a set of flip-flops of the same type, driven by the same clock pulse. • There can be external gates to control the inputs of the flip-flops.

  3. 4 bits Register with D flip-flops

  4. Registers (II) • Contents: series of bits • Length: a number of flip-flops • The flip-flops used usually transition on the clock pulse (ascending or descending). • Any sequential circuit can be made up of registers!

  5. Registers (III) • A register preserves the state! Value of the next state Register (state) Combinational Circuit C Inputs Outputs

  6. Realization with register & ROM • Design the following sequential circuit using a ROM and of a register • A1(t+1)(A1,A2,x) = A1x’ • A2(t+1)(A1,A2,x) = A2 Åx’ • y(A1,A2,x) = A2 x • Let us find the canonical SOP form = Sm(4, 6)= Sm(1, 2, 5, 6)= Sm(3, 7)

  7. Realization with register & ROM • 8x3 ROM and 2 bits registers (D flip-flops ) D1A1 Q1 D2A2 Q2 ROM8x3 0 22 21 1 x 20 2 y C

  8. Current State Input Next State Output A A x A A y 1 2 1 2 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 Calculation of the following state and y Transition Table

  9. Current State Input Next State Output A A x A A y 1 2 1 2 0 0 0 0 0 0 0 0 1 0 1 0 0 1 0 0 1 0 0 1 1 0 0 1 1 0 0 1 0 0 1 0 1 0 1 0 1 1 0 1 1 0 1 1 1 0 0 1 Calculation of next state and y Transition Table

  10. Adresses Output 2 1 0 2 2 2 0 1 2 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 Programming of the ROM Programming Table

  11. Adresses Output 2 1 0 2 2 2 0 1 2 0 0 0 0 0 0 0 0 1 0 1 0 0 1 0 0 1 0 0 1 1 0 0 1 1 0 0 1 0 0 1 0 1 0 1 0 1 1 0 1 1 0 1 1 1 0 0 1 Programming of the ROM * Count of transition just as it is!!!(with D flip-flopsonly)

  12. Several types of registers… • Shift registers • one-way (left or right-hand side) • bidirectional • Shift registers with loading • series or parallel • Built with RS, D, T, JK flip-flops … • From 1, 2, 3, 4, 8, 16… N bits

  13. Counters • Goes through a predetermined sequence of states. • Made up of flip-flops . • Useful in counting, the division of frequency of clock, and in the generation of unspecified sequences.

  14. Counters (II) • They have various characteristics: • Coding • binary, decimal, modulo M… • Mode • Asynchronous (ripple counter) • synchronous (all on the same clock signal) • With loading (or not) • Self-correcting (or not)

  15. Additional readings • In Mano and Kime: • Sections 5.1 to 5.3: registers • Sections 5.4 to 5.6: counters • Sections 7.1 to 7.5: transfer between registers

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