Presentation on theme: "SEQUENTIAL CIRCUITS USING TTL 74XX ICS"— Presentation transcript:
1 SEQUENTIAL CIRCUITS USING TTL 74XX ICS Flip Flops (IC 7474, IC 7473),Shift RegistersUniversal Shift Register(IC 74194)4- bit asynchronous binary counter(IC 7493).
2 Flip Flops (IC 7474, IC 7473) Difference between Latch and Flip-flop Latches are controlled by Enable signal and they are Level triggered, either positive or negative level triggered.Flip-flops use Pulse or Clock and it is Edge triggered.In Latches, output state is free to change according to input values, when active level is maintained at Enable input.In Flip-flops, output responds to the changes in input only at positive or negative edge of clock pulse at the clock input.
3 FLIP-FLOP:Flip-flops are synchronous bistable devices, also known as bistable multivibrator.Synchronous means output changes state only at a specified point on a triggering input called Clock(CLK), which is designated as a control input.Types:S-R Flip flopJ-K Flip flopD Flip flopT Flip flop
4 Edge Triggered S-R Flip flop SymbolTruth TableWave forms
5 Edge Triggered J-K Flip flop SymbolTruth TableWave forms
6 Edge Triggered D Flip flop Truth TableSymbolWave forms
9 Flip-Flop Applications Parallel Data storage:Several bits of data from parallel lines simultaneously is stored in a group of flip-flops.
10 2) Frequency Division:flip-flop is used to divide(reduce) the frequency of a periodic waveform.When a pulse waveform is applied to clock input of a J-K flip-flop that is connected to toggle (J=K=1), Q output is a square wave with one-half the frequency of the clock input.So, a single flip-flop can be applied as a divide-by-2 device.
11 3) Counting:Flip-flops are used in digital counters.
12 SHIFT REGISTERSShift registers consist of an arrangement of flip-flops which are used for storage and transfer of data.A Register, unlike counter has no specified sequence of states.A Register is used for storing and shifting data (1s and 0s) entered into it from an external source.DOES TWO FUNCTIONSDATA STORAGE [DONE BY FLIP-FLOPS]DATA MOVEMENT[LEFT, RIGHT AND DOWN]
22 Shift Register-Applications Time DelaySerial in/Serial out shift register is used to provide a time delay from input to output.8-bit serial in/serial out shift register is used with a clock frequency of 1MHz to achieve a time delay (td) of 8µs (8X1µs).
23 ExampleDetermine the amount of time delay between the serial input and each output in below fig. Show with timing diagramSol: Clock period is 2µs.Thus, the time delay can be increased or decreased in 2µs. increments from a minimum of 2µs to a maximum of 16µs
24 Serial data format 2) Serial to parallel data converter Serial data transmission from one digital system to another is commonly used to reduce the number of wires in the transmission line.A computer or microprocessor based system commonly requires incoming data to be in parallel format, thus the requirement for serial to parallel conversion.Serial data format
25 3) Universal Asynchronous Receiver Transmitter (UART) Computers and microprocessor-based system send and receive data in a parallel format. These systems must communicate with external devices that send and/or receive serial data. So, an interfacing device is used to do these conversions, which is called as UART.
27 Counters Asynchronous counter: Synchronous counter: Flip-flops can be connected together to perform counting operations, such a group of flip-flops is called as counter.Types:Asynchronous countersSynchronous counters.Asynchronous counter:It is also called as Ripple counter.In this, first flip-flop is clocked by the external clock pulse and then each successive flip-flop is clocked by the output of preceding flip-flop.Synchronous counter:In this, clock input is connected to all of the flip-flops so that they are clocked simultaneously.