08-08-2012, 04:48 PM
SEQUENTIAL LOGIC
[attachment=30655]
INTRODUCTION
We now introduce a new type of circuit that is constructed from devices that remember their
previous inputs. The logic circuits with combinational elements whose outputs are functions of their inputs only. Given a knowledge of a combinational circuit’s inputs and its Boolean function, we can always calculate the state of its outputs. The output of a sequential circuit depends not only on its current inputs, but also on its previous inputs. Even if we know a sequential circuit’s Boolean equations, we can’t determine its output state without knowing its past history (i.e. its previous internal states).The basic building blocks of sequential circuits are the flip-flop, bistable, and latch just as the basic building block of the combinational circuit is the gate.
It’s not our intention to deal with sequential circuits at anything other than an introductory
level, as their full treatment forms an entire branch of digital engineering. Sequential circuits can’t be omitted from introductory texts on computer hardware because they are needed to implement registers, counters, and shifters, all of which are fundamental to the operation of the central processing unit.
[attachment=30655]
INTRODUCTION
We now introduce a new type of circuit that is constructed from devices that remember their
previous inputs. The logic circuits with combinational elements whose outputs are functions of their inputs only. Given a knowledge of a combinational circuit’s inputs and its Boolean function, we can always calculate the state of its outputs. The output of a sequential circuit depends not only on its current inputs, but also on its previous inputs. Even if we know a sequential circuit’s Boolean equations, we can’t determine its output state without knowing its past history (i.e. its previous internal states).The basic building blocks of sequential circuits are the flip-flop, bistable, and latch just as the basic building block of the combinational circuit is the gate.
It’s not our intention to deal with sequential circuits at anything other than an introductory
level, as their full treatment forms an entire branch of digital engineering. Sequential circuits can’t be omitted from introductory texts on computer hardware because they are needed to implement registers, counters, and shifters, all of which are fundamental to the operation of the central processing unit.