Hola!
Good progress today, completed yesterday's last hours content and also covered three hours of Sequential Circuits. Will complete another hour also.
GOAL and DEADLINE is that should complete Number Systems by 10-07-2020 and start notes for DLD.
As we have seen SR yesterday i.e. Set-Reset FlipFlop, another type is JK FlipFlop which acts same as SR but is also define when JK=11 also unlike SR=11 is invalid JK=11 gives complement of Qpresent.
JK is again can be modified or seen as two broad types -> T(toggle) and D(delay) FlipFlops. These have an extensive application and role in the construction of counters.
Solve any question by tabling or constructing as follows:
Characteristic Equation -> Function Table-> Characteristic Table-> Excitation Table.
Another important concept is the conversion of a given FF to another FF:
Suppose,
AB is a given/existing/to be used to realize another FF and
CD is the target FF/new FF/to be constructed using given FF then,
CD should be realized using inputs of given FF AB.
Steps: (Here important thing is to know what is the FF to be constructed using what FF!)
1. Get the characteristic table of the target FF
2. Replace the next state using excitation of the given FF
3. Obtain the expression for the input of given FF and realize them.
Counters are used to provide accurate timing and control signals. Two types: synchronous and asynchronous.
For N states in a state diagram - > Ceil(logN) FFs are needed to realize it.
All the free running counters are Self-starting counters.
Synchronous:
In IC fabrication D-FFs are used. Technically, any flipflop can be used.
Also called shift counters.
Two types: Ring counter I0 = f(QN-1) and Johnson counter I0=f(QN-1 prime).
Johnson counter is also called as switch-tail ring counter. Can be used as gray counter since only one bit changes for every adjacent transition state in the state diagram.
Asynchronous:
In IC fabrication T-FFs are used. Technically, any flipflop can be used.
Also called ripple counters.
IC-7490 -> decade counter(%10 counter) and IC-7492 -> Hexadecimal counter(%16 counter)
binary-up counter (increasing order states) can be designed.
Hope it is not too technical but it is very important to know how these flipflops work since they are the basic building blocks of memory as well as some control systems like if OS wants to assign a resource through round-robin, then using counters we can make sure that each device is getting the resource for an equal amount of time. Okay! that's it for today.
Sayonara!!