Flip Flops

BRANCH : ELECTRONICS AND COMMUNICATION ENG. SUBJECT : DIGITAL ELECTRONICS TOPIC : FLIP FLOPS SUB TOPIC : List the common TTL/CMOS Flip- Flop. Ics 1 OBJECTIVES • On completion of this topic you would be able to know • the elimination of race condition, working of master slave J-K flip flop . • The different TTL technology and CMOS technology Flip-flop IC chips 2 Recap • Define Flip Flop • Mention the types of Flip flops • Draw backs of JK flip flop 3 J-K MASTER SLAVE FLIP- FLOP • A master slave flip flop is a combination of two clocked flip flops , the first is called the master and second is called slave. • Master is positively clocked and slave is negatively clocked. 4 On summarizing the working of J-K master slave flip flop, 1. While the clock is high ,the master is active ,and the slave is inactive. 2. While the clock is low , the master is inactive and the slave is active. 5 S J Q clk SLAVE MASTER Q K R R RR FIG(1) MASTER-SLAVE FLIP-FLOP 6 • In a master slave J-K flip flop assume low Q and high Q for an input clock high , the master goes in to the set state producing high ‘S’ and low ‘R’. • No change in Q and Q output . As the slave in inactive while the clock is high. • When clock goes low, the high ‘S’ and low ‘R’ forces the slave in to the set state producing a high Q and low Q. 7 • There are two distinct steps in setting the final Q output . • The Master is set while the clock is high. • The slave is set while the clock is low. • The truth table below in fig(2) ,shows that when clock is high & J=1, K=0 the flip flop set. • When clock is high , and J=0,K=1.the flip flop reset. • When clock is high and J=K=0, no change . • when clock is high J=K=1,then the flip flop toggles. 8 TRUTH TABLE OF J-K MASTER FLIP FLOP INPUTS OUTPUTS COMMENT CLK X J 0 0 1 1 K 0 1 0 11 Q(n+1) Qn 0 NO CHANGE RESET 1 SET Qn TOGGLE FIG(2) truth table of master-slave flip-flop 9 IC NUMBER FUNCTION 7473 Dual j-k Flip Flop 7474 Dual D Flip Flop 7475 Quad Bi-stable latch 7476 Dual j-k Flip Flop 10 IC NUMBER FUNCTION 74107 Dual j-k Flip Flop 74109 Dual j-k Flip Flop 74174 Hex D Flip Flop 74173 Quad D Flip Flop 11 Summary We discussed about • Race around condition • Working of master slave J-K Flip flop. • Flip Flop Ics 12 Quiz Master –slave JK Flip flop is a cascade connection of two clocked Flip flops. 13 Questions 1. How do you eliminate the race condition? 2. What is the advantage of master slave flip flop? 3. What is the state called when J and K are high along with clock in master slave J-K flip flop? 14