电子信息类专业英语 教学课件 ppt 作者 温丹丽 unit 2 passage two

1、电子信息类专业英语,http:/,机械工业出版社同名教材配套电子教案,温丹丽 高源 制作,机械工业出版社 http:/,Passage Two Digital Logic Circuits,1.Why can we say the binary system is the primary language of the computer? 2.What is the difference between the AND gate and the NAND gate?,Passage Two Digital Logic Circuits,Words and Expressions flip-flop 5flipflCp n. 触发器 latch lAt n. 锁存器 asynchronous eIsiNkrEnEs a. 电异步的 arbitrary 5:bitrEri a. 任意的，武断的 synchronous 5siNkrEnEs a. 同时的，同步的 arrangement E5reIn n. 电路，装置,机械工业出版社 http:/,Passage Two Digital Lo

2、gic Circuits,Text 1. Number Systems The number system with which we are most familiar is the base 10, or decimal system. Recent technological developments have created the need for other number systems. The electronic computer, for example, required the development of system that was easily adapted to electronic processes. These number systems were the binary (base 2), octal (base8), and hexadecimal (base 16). The binary system is the primary language of the computer. The octal and hexadecimal s

3、ystems are usually used for communication with the computer and for storage of information within the computer. Since computers can only process binary numbers or numbers coded in other systems such as octal and hexadecimal, the decimal system must be converted to one of these other systems before it can be processed by computer. When the computer finishes its operations on the information, the output is printed or displayed in number system other than decimal, and this too must be converted, th

4、is time back to the decimal system.,机械工业出版社 http:/,Passage Two Digital Logic Circuits,Digital electronics is a “logical” science. Logic, generally speaking, is the science of formal principles of reasoning. Digital logic is the science of reasoning with numbers a special circuit called a gate which can perform nearly all-digital functions. If the logic operation is too complex for one gate, it can almost always be implemented through the use of a combination of gates. These extended logic circui

5、ts are combinational logic.,机械工业出版社 http:/,Passage Two Digital Logic Circuits,2. Logical Gates (1) AND gate and NAND gate Two of the most basic logic functions are the AND and the NAND. The difference between these functions is that they are complements. This means they are opposite in function. The AND gate provides a function in digital logic which gives a high output when all of its inputs are high. Fig.2-1 shows the symbol used to represent an AND gate. In this case, there are two inputs, A

6、and B, and one output, C. Gates with as many as eight inputs are available.,机械工业出版社 http:/,Passage Two Digital Logic Circuits,An AND gate will provide an output high (1) only when both inputs (or all inputs if there are more than two) are high (1). This relationship is usually written in the following way: AB=C Above expressing is normally said in the following way: “if A equals 1 and B equals 1 then C will equal 1” or “ A and B equal C ”. The NAND gate is a more common gate than the AND gate (F

7、ig.2-2). It is the complement of the AND gate, meaning that it is just the opposite in logic state.,机械工业出版社 http:/,Passage Two Digital Logic Circuits,Fig.2-1 AND Gate,Fig.2-2 NAND Gate,机械工业出版社 http:/,Passage Two Digital Logic Circuits,NAND gates frequently are cheaper and easier to use than AND gates because electronically they are simpler. The N in front of the AND means “not” AND. The logic is also written differently for a N gate when it is placed in a formula. An overscore of bar is used to

8、indicate a NOT or inverted (complement) condition. For example:,机械工业出版社 http:/,Passage Two Digital Logic Circuits,It means “A and B equals NOT C”. In the case of the NAND gate the output will be high (1) except when the inputs are all high. When all inputs are high, the output of the NAND gate will be low (0). （2）OR gate The OR gate (Fig.2-3) provides a function that will give a high output (1) when any one of the inputs is at a high (1) logic level. This function as usually written in the follo

9、wing way: A+B=C The plus (+) sign is the symbol used to indicate an OR logic function. This expression is spoken in the following way: “if A OR B equals 1 then C equals 1 ”.,机械工业出版社 http:/,Passage Two Digital Logic Circuits,Fig.2-3 OR Gate,机械工业出版社 http:/,Passage Two Digital Logic Circuits,（3）Combining logic functions Individual logic gates are building blocks. They can stand alone if only a single logic function is needed, or they can be combined with other gates for more complex operations. There are times when it is advantageous to substitute one kind of gate for another. What does a circuit designer do, for instance, if a AND gate is needed and

《电子信息类专业英语 教学课件 ppt 作者 温丹丽 unit 2 passage two》由会员E****分享，可在线阅读，更多相关《电子信息类专业英语 教学课件 ppt 作者 温丹丽 unit 2 passage two》请在金锄头文库上搜索。