Introduction to Digital Logic Missouri S&T University CPE 2210 Registers

Transcription

1 Introduction to Digital Logic Missouri S&T University CPE 2210 Registers Egemen K. Çetinkaya Department of Electrical & Computer Engineering Missouri University of Science and Technology 24 October 2016 rev Egemen K. Çetinkaya

2 Introduction Datapath components Registers Summary Registers Outline 2

3 Digital Logic Systems Overview Combinatorial logic circuits for no memory systems Boolean algebra to mathematically design/analyze logic gates are building blocks Sequential logic circuits for memory systems Finite State Machines to mathematically design/analyze flip-flops and latches store memory flip-flops and latches are building blocks of sequential logic Sequential logic circuits (aka controllers) combine combinatorial circuits storage elements (e.g. registers) 3

4 Digital Systems Components analog phenomena electric signal A2D digital data digital data sensors and other inputs Digital System D2A electric signal actuators and other outputs digital data digital data Transducer: sensor + actuator Not all sensors/actuators require A2D/D2A conversion Digital system can be implemented: microprocessor readily available, cheap, easy to program, easy to reprogram custom circuit smaller, faster, consume less power 4

5 Digital Systems Paths Digital systems have two paths: datapath circuit control circuit Datapath circuit store data manipulate data transfer data from one part to another Control circuit controls the operation of datapath circuit 5

6 Datapath Components Building Block examples What are some examples of datapath components? 6

7 Registers Shifters Counters/timers Datapath Components Building Block examples Multiplexer/demultiplexers Decoders/encoders Adders Comparators Subtractors ALUs: Arithmetic Logic Units 7

8 Storing Multiple Bits Registers Register: multiple flip-flops sharing common clock N-bit register stores N bits N is called register width (also number of flip-flops!!!) Generally 8, 16, 32 bits wide Example: 4-bit register I3 I2 I1 I0 clk D Q D Q D Q 4-bit register D Q I3 I2 I1 I0 reg(4) Q3 Q2 Q1 Q0 Q3 Q2 Q1 Q0 8

9 Registers Operations Register: multiple flip-flops sharing common clock N-bit register stores N bits N is called register width Generally 8, 16, 32 bits wide Two operations: writing (aka: loading, storing) changing bits inside the register reading observing the register outputs 9

10 Registers Buses Register: multiple flip-flops sharing common clock N-bit register stores N bits N is called register width N-bit bus: N wires to carry N-bit data item Drawing convention: with a small angled cross line ld 8 10

11 Shift register Registers Types Serial-in/serial-out shift register Serial-in/parallel-out shift register Parallel-in/serial-out shift register Parallel-in/parallel-out shift register Universal register Rotating register 11

12 LSB: Least Significant Bit right-most bit MSB: Most Significant Bit higher-order bit left-most bit Registers LSB vs. MSB Example: where is LSB and MSB?

13 LSB: Least Significant Bit right-most bit MSB: Most Significant Bit higher-order bit left-most bit Example: LSB MSB Registers LSB vs. MSB

14 Registers Shift Register Moves a stored bit to right or left Shift right operation: inserts a new zero on MSB and drops LSB Shift left operation: insets a new zero on LSB and drops MSB 14

15 Shift Register Shift Right Operation Example Lets shift right one

16 Shift Register Shift Right Operation Example Lets shift right one After moving one bit to right? 16

17 Shift Register Shift Right Operation Example Lets shift right one After moving one bit to right Added 0 for MSB dropped the LSB 17

18 Shift Register Shift Right Operation Example Lets shift right 2-bits After first shift right After second shift right 18

19 Shift Register Shift Right Operation Example Lets shift right 2-bits After first shift right After second shift right 19

20 Shift Register Shift Right Operation Example Lets shift right 2-bits After first shift right After second shift right

21 Shift Register Shift Right Operation Example What was the arithmetic operation we just did? 21

22 Shift Register Shift Right Operation Example Shift right n-bits will divide by 2 n 22

23 Lets shift left one Shift Register Shift Left Operation Example

24 Lets shift left one Shift Register Shift Left Operation Example After moving one bit to left? 24

25 Lets shift left one Shift Register Shift Left Operation Example After moving one bit to left dropped the MSB added 0 for LSB 25

26 Lets shift left 2-bits Shift Register Shift Left Operation Example After first shift left After second shift left 26

27 Lets shift left 2-bits Shift Register Shift Left Operation Example After first shift left After second shift left 27

28 Lets shift left 2-bits Shift Register Shift Left Operation Example After first shift left After second shift left

29 Shift Register Shift Left Operation Example What was the arithmetic operation we just did? 29

30 Shift Register Shift Left Operation Example Shift left n-bits will multiply by 2 n 30

31 Shift Register Directionality Does a shift register shift only one direction (unidirectional?) 31

32 Shift Register Directionality Registers can be bidirectional as well A control input will decide to shift right or left 32

33 Shift Register Serial-Input Serial-Output Register Serial-input serial-output unidirectional register 33

34 Shift Register Serial-Input Parallel-Output Register Serial-input parallel-output unidirectional register 34

35 Shift Register Parallel-Input Serial-Output Register When Load/Shift is 0, parallel data in When Load/Shift is 1, cascading occurs, i.e. serial output 35

36 Bidirectional shift register Shift Register Universal Shift Register 36

37 Registers Rotating Register Shift: moves a stored bit to right or left shift right operation: inserts a new zero on MSB and drops LSB shift left operation: insets a new zero on LSB and drops MSB Rotation: shifts but does not drops rotate right operation: LSB becomes the new MSB shift left operation: MSB becomes the new LSB 37

38 Rotating Register Rotate Right Operation Example Lets rotate right one

39 Rotating Register Rotate Right Operation Example Lets rotate right one After rotating one bit to right? 39

40 Rotating Register Rotate Right Operation Example Lets rotate right one After rotating one bit to right LSB became the new MSB after shifting 40

41 Rotating Register Rotate Right Operation Example Lets rotate right 2-bits After first right rotation After second right rotation 41

42 Rotating Register Rotate Right Operation Example Lets rotate right 2-bits After first right rotation After second right rotation 42

43 Rotating Register Rotate Right Operation Example Lets rotate right 2-bits After first right rotation After second right rotation

44 Rotating Register Rotate Left Operation Example Lets rotate left one

45 Rotating Register Rotate Left Operation Example Lets rotate left one After rotating one bit to left? 45

46 Rotating Register Rotate Left Operation Example Lets rotate left one After rotating one bit to left MSB became the new LSB after shifting 46

47 Rotating Register Rotate Left Operation Example Lets rotate left 2-bits After first left rotation After second left rotation 47

48 Rotating Register Rotate Left Operation Example Lets rotate left 2-bits After first left rotation After second left rotation 48

49 Rotating Register Rotate Left Operation Example Lets rotate left 2-bits After first left rotation After second left rotation

50 Registers Summary Registers store multiple bits a flip-flop stores only one bit Several types of registers exist serial/parallel I/O combinations directional (right or left)/bidirectional Important operations using registers: shift: right: divide operation left: multiply operation rotation does not drop LSB or MSB, substitutes 50

51 References and Further Reading [V2011] Frank Vahid, Digital Design with RTL Design, VHDL, and Verilog, 2nd edition, Wiley, [BV2009] Stephen Brown and Zvonko Vranesic, Fundamentals of Digital Logic with VHDL Design, 3rd edition, McGraw-Hill, [G2003] Donald D. Givone, Digital Principles and Design, McGraw-Hill,

52 End of Foils 52