Digital Electronics NUMBER SYSTEM BINARY CODES BOOLEAN ALGEBRA K MAPS COMBINATIONAL CKT SEQUENTIAL CIRCUITS INTRODUCTION CLOCK BISTABLE MULTIVIBRATOR DERIVATION of FLIPFLOP circuit RS FLIPFLOP RS FLIPFLOP(NAND IMPLEMENTATION) R'S' FLIPFLOP Clocking RS LATCH Other LATCHes Timing problem in LATCHES ASYNCHRONUS INPUTS Parameters of CLOCK pulse QUESTIONS(LATCH using MUX) EDGE SENSITIVE LATCH (i.e. FLIPFLOP) MASTER SLAVE FF D FF USING MUX TIMING PARAMETERS OF FF CHARACTERISTIC EQUATIONS OF FFs EXCITATION TABLES OF FF CONVERSION OF 1 FF TO OTHER FF as 1bit MEMORY CELL REGISTERS SHIFT REGISTERS RING COUNTER JOHNSON COUNTER QUESTION(Serial Data transfer) ASYNCHRONOUS COUNTERS RIPPLE COUNTER COUNTER other than MOD-2n Designing COUNTER Using K-MAPS QUESTION(MOD 6 counter) QUESTION(Counter design) DOWN COUNTER QUESTION(Counter design) GLITCH SYNCHRONOUS COUNTER COMPARISON B/W SYNC. & ASYNC. COUNTERS CLOCK SKEW QUESTION(Maximum frequency question) QUESTION(Maximum frequency question) MORE QUESTIONS TIMING CIRCUITS

USING K-MAPS TO DESIGN COUNTER

Q- Design MOD-3 ripple counter using (a) Observing outputs (b) K-maps to design the circuit.

Ans: (a)We can design the MOD 3 counter using 2 FFs as 3 is less than 4 i.e. 22 and greater than 2. We can see directly that as we have to reset the counter only after 2 i.e. when output is 3 we reset the counter and hence we need to reset only when we have Q0= 1 & Q1=1. Now firstly design MOD-4 counter using 2 FFs and then take NAND of Q0 & Q1 and feed the output to CLEAR of both FFs.

(b) We firstly draw state diagram of the counter required as:

And we have the general circuit to design the other than MOD 2 n then we have the general circuit as

And now we draw a table to list the different input combinations to Combinational circuit and their corresponding output as:

Q1          Q0                          OUTPUT of reset logic

0              0                              1

0              1                              1

1              0                              1

1              1                              0

And using K-map as

And hence we get the whole circuit for MOD-3 counter as