Sequential Logic

The Toggle Flip-flop is another type of bistable sequential logic circuit based around the previous clocked JK flip-flop circuit. The toggle flip-flop can be used as a basic digital element for storing one bit of information, as a divide-by-two divider or as a counter. Toggle flip-flops have a single input and one…

We have seen throughout this Electronics Tutorial section on Sequential Logic that a flip-flop will remain in one of its two stable states indefinitely until some form of external trigger pulse is applied to make it change state. As flip-flops are bistable devices, these sequential circuits are sometimes called “latches” because their…

In the previous Shift Register tutorial we saw that if we apply a serial data signal to the input of a Serial-in to Serial-out Shift Register, the same sequence of data will exit from the last flip flip in the register chain. This serial movement of data through the resister occurs…

This sequential device loads the data present on its inputs and then moves or “shifts” it to its output once every clock cycle, hence the name Shift Register. A shift register basically consists of several single bit “D-Type Data Latches”, one for each data bit, either a logic “0” or a “1”, connected…

One of the main disadvantages of the basic SR NAND Gate Bistable circuit is that the indeterminate input condition of SET = “0” and RESET = “0” is forbidden. This state will force both outputs to be at logic “1”, over-riding the feedback latching action and whichever input goes to logic level…

Individual Sequential Logic circuits can be used to build more complex circuits such as Multivibrators, Counters, Shift Registers, Latches and Memories. But for these types of circuits to operate in a “sequential” way, they require the addition of some form of clock pulse or timing signal to cause them to change their…

The basic S-R NAND flip-flop circuit has many advantages and uses in sequential logic circuits but it suffers from two basic switching problems. 1. the Set = 0 and Reset = 0 condition (S = R = 0) must always be avoided 2. if Set or Reset change state while the enable (EN) input is high the correct…

Unlike Combinational Logic circuits that change state depending upon the actual signals being applied to their inputs at that time, Sequential Logic circuits have some form of inherent “Memory” built in. This means that sequential logic circuits are able to take into account their previous input state as well as those actually present, a…