1. CSI-2111 Computer Architecture Ipage 7-1 7. Sequential circuits, 2nd part v Objectives: To recognize and know to use the principal types of sequential circuits u Registers u Counters u Generators of imposed sequences

2. CSI-2111 Computer Architecture Ipage 7-2 Registers v Are sequential circuit capable of storing information of several bits (word). v Made of a set of flip-flops of the same type, driven by the same clock pulse. v There can be external gates to control the inputs of the flip-flops.

3. CSI-2111 Computer Architecture Ipage 7-3 4 bits Register with D flip-flops

4. CSI-2111 Computer Architecture Ipage 7-4 Registers (II) v Contents: series of bits v Length: a number of flip-flops v The flip-flops used usually transition on the clock pulse (ascending or descending). v Any sequential circuit can be made up of registers!

5. CSI-2111 Computer Architecture Ipage 7-5 Registers (III) v A register preserves the state! Combinational Circuit Register (state) C InputsOutputs Value of the next state

6. CSI-2111 Computer Architecture Ipage 7-6 Realization with register & ROM v Design the following sequential circuit using a ROM and of a register – A 1(t+1) (A1,A2,x) = A 1 x’ – A 2(t+1) (A1,A2,x) = A 2  x’ – y(A1,A2,x) = A 2 x v Let us find the canonical SOP form =  m(4, 6) =  m(1, 2, 5, 6) =  m(3, 7)

7. CSI-2111 Computer Architecture Ipage 7-7 Realization with register & ROM v 8x3 ROM and 2 bits registers (D flip- flops ) ROM 8x3 D 1 A 1 Q 1 D 2 A 2 Q 2 C xy 0 1 2 2 2121 2020

8. CSI-2111 Computer Architecture Ipage 7-8 Calculation of the following state and y Transition Table

9. CSI-2111 Computer Architecture Ipage 7-9 Calculation of next state and y Transition Table

10. CSI-2111 Computer Architecture Ipage 7-10 Programming of the ROM Programming Table

11. CSI-2111 Computer Architecture Ipage 7-11 Programming of the ROM * Count of transition just as it is!!! (with D flip-flops only)

12. CSI-2111 Computer Architecture Ipage 7-12 Several types of registers… v Shift registers –one-way (left or right-hand side) –bidirectional v Shift registers with loading –series or parallel v Built with RS, D, T, JK flip-flops … v From 1, 2, 3, 4, 8, 16… N bits

13. CSI-2111 Computer Architecture Ipage 7-13 Counters v Goes through a predetermined sequence of states. v Made up of flip-flops. v Useful in counting, the division of frequency of clock, and in the generation of unspecified sequences.

14. CSI-2111 Computer Architecture Ipage 7-14 Counters (II) v They have various characteristics: –Coding u binary, decimal, modulo M… –Mode u Asynchronous (ripple counter) u synchronous (all on the same clock signal) –With loading (or not) –Self-correcting (or not)

15. CSI-2111 Computer Architecture Ipage 7-15 Additional readings v 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