chapter 3: sequential logic circuit – shift register - ekt 121 / 4 elektronik digit 1

Chapter 3: Chapter 3: Sequential Logic Circuit Sequential Logic Circuit

– – Shift Register -Shift Register -

EKT 121 / 4EKT 121 / 4ELEKTRONIK DIGIT 1ELEKTRONIK DIGIT 1

© Copyright 2000 Indiana University Board of Trustees

Basic shift register function Serial in / serial out shift registers Serial in / parallel out shift registers Parallel in / serial out shift registers Parallel in / parallel out shift registers Bidirectional shift registers Shift register applications

3.2 Shift Register


Sequential Logic CircuitsSequential Logic Circuits

Combinational logic

Memory elements

Combinational outputs Memory outputs

Inputs

Sequential circuit = Combinational logic + Memory Elements

Current State of A sequential Circuit: Value stored in memory elements (value of state variables).

State transition: A change in the stored values in memory elements thus changing the sequential circuit from one state to another state.


A register is a memory device that can be used to store more than one-bit information

A register is usually realized as several flip-flops with common control signals that control the movement of data to and from the register

……….

RegistersRegisters


RegistersRegisters An n-bit register is a collection of n D

flip-flops with a common clock used to store n related bits.

D 1QCLR

Q

Q /1Q1D

D 2QCLR

Q

Q /2Q2D

D 3QCLR

Q

Q /3Q3D

D 4QCLR

Q

Q /4Q4D

CLK

/CLR

74LS175Example: 74LS175 4-bit register

CLKCLR

4Q4Q3Q3Q2Q2Q1Q1Q

74LS175

1D

2D

3D

4D


Shift RegistersShift Registers

Multi-bit register that moves stored data bits left/right ( 1 bit position per clock cycle)

0 1 1 1 LSI

Q3 Q2 Q1 Q0

1 1 1 LSI

Q3 Q2 Q1 Q0

RSI 0 1 1 1

Q3 Q2 Q1 Q0

RSI 0 1 1

Q3 Q2 Q1 Q0

– Shift Right (or Shift Up) is towards MSB

– Shift Left is towards MSB


Basic Shift Register FunctionsBasic Shift Register Functions

Consist of an arrangement of flip-flops Important in applications involving

storage and transfer of data (data movement) in digital system

Used for storing and shifting data (1s and 0s) entered into it from an external source and possesses no characteristic internal sequence of states.

D flip-flops are use to store and move data


The flip-flop as a storage The flip-flop as a storage elementelement

When a 1 is on D, Q becomes a 1 at triggering edge of CLK or remains a 1 if already in the SET state

When a 0 is on D, Q becomes a 0 at triggering edge of CLK or remains a 0 if already in the RESET state


Basic data movement in shift Basic data movement in shift registersregisters

(Four bits are used for illustration. The bits move in (Four bits are used for illustration. The bits move in the direction of the arrows.)the direction of the arrows.)


Types of Shift RegisterTypes of Shift Register

1. Serial In / Serial Out Shift Registers (SISO)2. Serial In /Parallel Out Shift Registers (SIPO)3. Parallel In / Serial Out Shift Registers

(PISO)4. Parallel In / Parallel Out Shift Registers

(PIPO)


Serial In, Serial Out Shift Serial In, Serial Out Shift RegisterRegister(SISO)(SISO)

D Q

CLK

D Q

CLK

D Q

CLK

SERIN

CLOCK

SEROUT

For a n-bit SRG:Serial Out = Serial In delayed by n clock period

4-bit shift register example:serin: 1 0 1 1 0 0 1 1 1 0serout: - - - - 1 0 1 1 0 0clock:

SRG n>SI SO


Serial In, Serial Out Shift Serial In, Serial Out Shift RegisterRegister(SISO)(SISO)


Serial In, Serial Out Shift Serial In, Serial Out Shift RegisterRegister (SISO)(SISO)


Serial In, Parallel Out Shift Serial In, Parallel Out Shift registerregister (SIPO)(SIPO)

D Q

CLK

D Q

CLK

D Q

CLK

SERIN

CLOCK

nQ

2Q

1Q

Serial to Parallel Converter

Example: 4-bit shift register serin: 1 0 1 1 0 0 1 1 1 01Q: - 1 0 1 1 0 0 1 1 12Q: - - 1 0 1 1 0 0 1 13Q: - - - 1 0 1 1 0 0 14Q: - - - - 1 0 1 1 0 0clock:

SRG n>SI 1Q

2Q

nQ (SO)


Serial In, Parallel Out Shift registerSerial In, Parallel Out Shift register (SIPO)(SIPO)

• Data bits entered serially (right-most bit first)

• Difference from SISO is the way data bits are taken

out of the register – in parallel.

• Output of each stage is available


ExampleExample : :

The states of 4-bit register (SRG 4) for the data input The states of 4-bit register (SRG 4) for the data input and clocks waveforms. and clocks waveforms.

Assume the register initially contains all 1s


Parallel In, Serial Out Shift Parallel In, Serial Out Shift RegisterRegister(PISO)(PISO)

SERIN

CLOCK

D Q

CLK

D Q

CLK

D Q

CLK

SEROUT

LOAD/SHIFT

1D

2D

ND

S

L

S

L

S

L

1Q

2Q

NQ

Parallel to Serial Converter

Load/Shift=1 Di Qi

Load/Shift=0 Qi Qi+1


4-bit parallel in/serial out shift 4-bit parallel in/serial out shift registerregister(PISO)(PISO)


Parallel In, Parallel Out Shift Parallel In, Parallel Out Shift RegisterRegister(PIPO)(PIPO)

SERIN

CLOCK

D Q

CLK

D Q

CLK

D Q

CLK

LOAD/SHIFT

1D

2D

ND

1Q

2Q

NQ

S

L

S

L

S

L

General Purpose:Makes any kind of (left) shift register


Parallel In, Parallel Out Shift Parallel In, Parallel Out Shift Register (PIPO)Register (PIPO)

Immediately following simultaneous entry of all data bits,it appear on parallel output.


Bi-directional Shift RegistersBi-directional Shift Registers

Data can be shifted left Data can be shifted right A parallel load maybe possible 74HC194 is an bidirectional universal

shift register


Bi-directional Universal Shift Bi-directional Universal Shift RegistersRegisters

4-bit Bi-directional Universal (4-bit) PIPO

CLK CLR S1 S0

LIN D QDC QCB QBA QARIN

11

1

10

9

7

6

4

5

3

2

12

13

14

15

74x194Modes:HoldLoadShift RightShift Left

R L

Mode Next state

Function S1 S0 QA* QB* QC* QD*

Hold 0 0 QA QB QC QDShift right/up 0 1 RIN QA QB QCShift left/down 1 0 QB QC QD LINLoad 1 1 A B C D


Four-bit Johnson countersFour-bit Johnson counters Serial output

connected back toserial input

The complement of the output (Q’) is fedback into

1st FF.


Five-bit Johnson countersFive-bit Johnson counters


A 10-bit ring counter A 10-bit ring counter Assume initial state : 1010000000


Shift Register ApplicationsShift Register Applications State Registers

– Shift registers are often used as the state register in a sequential device. Usually, the next state is determined by shifting right and inserting a primary input or output into the next position (i.e. a finite memory machine)

– Very effective for sequence detectors Serial Interconnection of Systems

– keep interconnection cost low with serial interconnect Bit Serial Operations

– Bit serial operations can be performed quickly through device iteration

– Iteration (a purely combinational approach) is expensive (in terms of # of transistors, chip area, power, etc).

– A sequential approach allows the reuse of combinational functional units throughout the multi-cycle operation


Shift Register Applications Shift Register Applications Example:Example: Serial Interconnection of Serial Interconnection of SystemsSystems

Serial DATAParallel-to-serial converter

Parallel Data from

A-to-D converter

Serial-to-parallel converter

Parallel Data to D-to-A converter

Control

Circuits

CLOCK

/SYNC

TransmitterControl

Circuits

Receiver

n nOne bit


Shift Register Applications Shift Register Applications Example:Example: 8-Bit Serial Adder8-Bit Serial Adder

...7 6 5 0>

x7 x6 x5 x0

...7 6 5 0>

y7 y6 y5 y0

...7 6 5 0>

FACout S

Cin A BD Q

CLK

CLR

CLK

CLEAR_Cz7 z6 z5 z0...

CTL Sequential Implementation of:Z[7..0] = X[7..0] + Y[7..0]

V


Shift Register Applications Shift Register Applications Example:Example:

The shift register as a time-delay The shift register as a time-delay devicedevice


Shift Register Applications Example:Shift Register Applications Example: Simplified logic diagram of a Simplified logic diagram of a serial-to-parallel converterserial-to-parallel converter


Thank youThank you

chapter 3: sequential logic circuit – shift register - ekt 121 / 4 elektronik digit 1

Documents

q clr q q

d slide

shift register slide

q 74ls175

registers serial

shift registers sipo

shift registers pipo

d flipflops