DE_MF

Monostable m A Monostable Circuit produc in response to a trigger inpu output of the circuit stays in trigger input, hence the nam \"one stable state\". his type o \"push to operate\" system fo exhibitions. A visitor can pu mechanism moving, and the automatically switch off afte

mode ces one pulse of a set lengthut such as a push button. Then the low state until there is ame \"monostable\" meaning of circuit is ideal for use in aor a model displayed atush a button to start a model's e mechanism willer a set time. 17

Monostable m

mode 18

Bistable Mode (or Schm A Bistable Mode or what is some two stable states, high and low. T the output of the circuit go into the low makes the output of the circu circuit is ideal for use in an autom the train is required to run back a track. A push button (or reed swit of the train) would be placed at ea one is hit by the train, it will either output of the 555 would control a as a reversing switch to reverse t thereby reversing the direction of

mitt Trigger) etimes called a Schmitt Trigger, has Taking the Trigger input low makes e high state. Taking the Reset input uit go into the low state. This type of mated model railway system where and forth over the same piece of tch with a magnet on the underside ach end of the track so that when r trigger or reset the bistable. The DPDT relay which would be wired the direction of current to the track, f the train 19

Bistable Mode (or Schm

mitt Trigger) 20

7.5 Application of Timin Applications of 555 timers timers, missing pulse dete touch switches, freque measurement, pulse width m The IC 555 is used widel circuits. The 555 timer integrated circuit which ca different circuits.

ng Circuits in monostable mode includeection, bounce free switches,ency divider, capacitancemodulation (PWM) etc.ly in different types of alarm is an extremely versatilean be used to build lots of 21

Thank

k You 22

Unit 8: Sequ circui

uential Logic its 1

8.1 Introduction to Counters are used for c connected together to perfo number of flip-flops used a connected determine the n specific sequence of sta through during each comple

Counters counting. Flip-flops can be orm counting operations. Theand the way in which they arenumber of states and also theatus that the counter goesete cycle. 2

 Like shift registers and other another important element in most. They are counters. Count but also for measuring frequen addresses . Counters are specially designed in which , the state of the counte circuit by the flip flops. Coun number that how many times an

r combinational circuits, there is digital electronics which we use ters are used not only for countingncy and time ; increment memory d synchronous sequential circuits, er is equal to the count held in thenters calculate or note down then event occurred. 3

Need of Coun Counting means increme values of an operator, with value. So to perform the m no devices other than count We cannot perform this act logic devices rather than co

ntersenting or decrementing theh respect to its previous state athematical operation we use ters. tion (counting) with any otherounters. 4

Modulus of a count Then counters are sequentia predetermined sequence of cou by an external clock (CLK) signa The number of states or count particular counter advances befo its original first state is called the In other words, the modulus (o states the counter counts and counter

teral logic devices that follow aunting states which are triggeredal.ting sequences through which a ore returning once again back toe modulus (MOD).or just modulo) is the number ofd is the dividing number of the 5

Modulus of a cou For example, a 2-bit coun 112 in binary, that is 0 to value of 4 ( 00 → 01 → 10 would therefore be called a Note also that it has taken to 11.

unternter that counts from 002 to 3 in decimal, has a modulus → 11 , return back to 00 ) so modulo-4, or mod-4, counter. 4 clock pulses to get from 00 6

Modulus of a coun Therefore, a “Mod-N” counter w connected together to count a 2n different output states, (n is t always a whole integer value. The we can see that MOD cou is an integral power of 2, that is an n-bit counter depending on t how they are connected, deter the counter.

nterwill require “N” number of flip-flopsa single data bit while providingthe number of bits). Note that N isunters have a modulus value thats, 2, 4, 8, 16 and so on to produce the number of flip-flops used, and rmining the type and modulus of 7



8

Types of coun There are two types of c circuits, they are – Synchronous counters – Asynchronous counters

nters counters available for digital 9

Synchronous cou• The counters which use c transition are called “Synchr• This means the synchronou clock input to change state synchronous counters are signal.