Chapter 6 – Digital ElectronicsChapter 6 – Digital Electronics – Part 1– Part 1

1. D (Data) Flip Flops2. RS (Set-Reset) Flip Flops3. T Flip Flops4. JK Flip Flops5. JKMS Flip Flops

InformationInformation Registers Registers

Flip-flop

1) may also refer to the bistable multivibrator, a circuit with two stable states (output).

2) Flip flips are used to store data (or information).

3) Different types of flip flops serve different functions.

4) Flip flops can be defined with characteristic functions.

• Flip flips store data on a rising or falling trigger edge.– Example: control input transitions from 0 1,

data input appears at output– Data remains stable in the flip flop until next

rising edge.

Data Storage

Lo-HiLo-Hi edgeHi-LoHi-Lo edge

A clock is a circuit that outputs 0’s and 1’s at specific frequencies

A clock

Latches FF

Latches are Level Sensitive

Out put is constantly affected by the input as long as enable is assertive.When enabled, their content changes immediately when input changes.

sensitive to the duration of pulse and can transfer data until they are switched on.

used as temporary buffers.

One latch stores one bit of informationMain types of latches are SR, D, JK, and T.

Flip-Flops are Edge Sensitive.

Content changes only either At the rising or falling edge of the enable signal.Enable signal is usually the controlling clock signal.

sensitive to signal change (low to high or high to low) and not the level.

used as registers. 

One FF stores one bit of informationMain types of flip flops are SR, D, JK, and T.

Latches and Flip Flops A clock

The outputs of any single-bit latch or memory are traditionally designated Q and Q'. In a commercial latch circuit, either or both of these may be available for use by other circuits. In any case, the circuit itself is:

                                                                                   1) The Basic RS Latch

NAND Latch

NOR Latch

The Clocked RS NAND Latch

The Edge-Triggered RS Flip-Flop

Symbols

The D Latch & Flip Flop

0 1 0 11 1 1 0X 0 Q0 Q0

D C Q Q

When C is high, D passes from input to output (Q).

Lo-HiLo-Hi edgeHi-LoHi-Lo edge

The D Flip-Flop

C

D Q

Q’0 0 11 1 0X 0 Q0 Q0’

D C Q Q’

Positive edge triggered

D Flip-Flop

D gets latched to Q on the rising edge of the clock.

The JK Flip-Flop

Symbols

• Flip flops are powerful storage elements– They can be constructed from gates and latches!

• D flip flop is simplest and most widely used• Asynchronous inputs allow for clearing and presetting the

flip flop output• Multiple flops allow for data storage

– The basis of computer memory!• Combine storage and logic to make a computation circuit• Next time: Analyzing sequential circuits.

Random-Access Memory

Can read and write at any point in memoryImplemented using D Flip-Flops

Register

Used to hold one item of informationCPU’s have many registers

Clocks

A clock is a circuit that outputs 0’s and 1’s at specific frequencies

Negative-Edge-Triggered T Flip-Flop

PRE

C LR

Q

QT

(a ) (b )

V C

C

PRE

CLR

Q

QC

J

K

Latch and Flip-flop Timing

S et

R e se t

(a )

(b )

C lo ck

Q

S e t

R ese t

Q