Logic Devices and Design

Digital electronics is a major field in electronics that deals with logic design. Sequential logic devices and state machines are used to come up with digital designs that can be used in many diverse ways. There are two kinds of designs in digital electronics; sequential logic design and combinational logic design. Sequential logic differs from combinational logic in that both present and past inputs determine the output of the logic device. This means for the device output to depend on the present inputs and its present internal state, it must have some kind of a memory of its previous inputs. This can be any device that remembers that a signal of logic level 1 or 0 is connected to its inputs and is made available to the output. These memory devices are called OR gates.

In order to describe the behavior of a sequential device, a state table is used. In logic design, this used to show all the possible state and inputs and the state the device enters after an input. Memory units employ what is called feedback and this is characteristic of all memory devices that can be programmed. In fact, without feedback, there would not be any permanent memory device in electronics. In their most basic forms, memory circuits are called flip flops or latches. The JK is the most versatile flip-flop and is the mot commonly used. It has no undefined states and it has two data inputs, J and K, and a clock input. This type of flip-flop logic design is edge triggered on the falling clock edge. This kind of flip flop is the most commonly used because it has a simpler logic design that ensures that the state changes properly in a circuit.

In sequential logic there are also other devices called registers that can do a bunch of things. Some common registers include data registers, shift registers, counters and synchronous counters. In a practical way, data registers are used to hold numeric values such as floating point and integer values. Other logic devices include state machines. These logic devices depend on variables and immediate inputs to output a state. In a counter, the sate variables are the values that have been stored in the flip flops. Again, the logic design of state machines is completely defined by the use of a state table. Programming logic design has undoubtedly seen much advancement and its uses have likewise expanded.