{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Sequential Logic

# Sequential Logic - 03-CLements-Chap03.qxd 11:10 PM Page 101...

This preview shows pages 1–2. Sign up to view the full content.

3 Sequential Logic CHAPTER MAP 2 Logic elements and Boolean algebra We begin our introduction to the computer with the basic building block from which we construct all computers, the gate. A combinational digital circuit such as an adder is composed of gates and its output is a Boolean (logical) function of its inputs only. 3 Sequential logic The output of a sequential circuit is a function of both its current inputs and its past inputs; that is, a sequential circuit has memory. The building blocks used to construct devices that store data are called ﬂip-ﬂops. In this chapter we look at basic sequential elements and the counters, registers, and shifters that are constructed from ﬂip-ﬂops. 4 Computer arithmetic Computer arithmetic concerns the representation of numbers in a computer and the arithmetic used by digital computers.We look at how decimal numbers are converted into binary form and the properties of binary numbers and we demonstrate how operations like addition and subtraction are carried out.We also look at how computers deal with negative numbers and fractional numbers. 5 The instruction set architecture In this chapter we introduce the computer’s instruction set architecture (ISA), which describes the low-level programmer’s view of the computer.The ISA describe the type of operations a computer carries out.We are interested in three aspects of the ISA: the nature of the instructions, the resources used by the instructions (registers and memory), and the ways in which the instructions access data (addressing modes).The 68K microprocessor is used to illustrate the operation of a real device. INTRODUCTION We now introduce a new type of circuit that is constructed from devices that remember their previous inputs.The logic circuits in Chapter 2 were all built 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.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern