1、Chapter 4,Gates and Circuits 門和電路,42,Chapter Goals本章目標,Identify the basic gates and describe the behavior of each 識別基礎的門，描述每種門的行為 Describe how gates are implemented using transistors 描述如何用晶體管實現(xiàn)門 Combine basic gates into circuits 用基礎門組合電路,43,Chapter Goals本章目標,Describe the behavior of a gate or circui

2、t using Boolean expressions, truth tables, and logic diagrams 用Boolean表達式、真值表和邏輯框圖描述門或電路。 Compare and contrast a half adder and a full adder 比較半加器和全加器之間的異同點 Describe how a multiplexer works 描述多路復用器是如何工作的,44,Chapter Goals本章目標,Explain how an S-R latch operates解釋如何操作S-R鎖存器 Describe the characteristics

3、of the fourth generations of integrated circuits 描述第四代集成電路的特征,45,Computers and Electricity計算機和電學,Gate A device that performs a basic operation on electrical signals 門是對電信號執(zhí)行基礎運算的設備。 Circuits Gates combined to perform more complicated tasks 電路是由門組合而成的，可以執(zhí)行更加復雜的任務。,46,Computers and Electricity計算機和電學,T

4、here are three different, but equally powerful, notational methods for describing the behavior of gates and circuits 描述門和電路的表示法有三種，它們互不相同，但卻一樣有效： Boolean expressionsBoolean表達式 logic diagrams邏輯框圖 truth tables真值表,47,Computers and Electricity計算機和電學,Boolean expressions Expressions in Boolean algebra, a

5、mathematical notation for expressing two-valued logic 布爾表達式，布爾代數(shù)中的表達式，表示二值邏輯的數(shù)學表示法。 This algebraic notation are an elegant and powerful way to demonstrate the activity of electrical circuits 這種代數(shù)表示法是演示電路活動的極好方式。,48,Computers and Electricity計算機和電學,Logic diagram A graphical representation of a circuit

6、 Each type of gate is represented by a specific graphical symbol 邏輯框圖，一種電路的圖形化表示，每種類型的門有自己專用的符號。 Truth table A table showing all possible input value and the associated output values 真值表，列出了所有可能的輸入值和輸出值的表。,49,Gates門,Lets examine the processing of the following six types of gates 我們將分析下列6種類型的門 NOT非門

7、AND與門 OR或門 XOR異或門 NAND與非門 NOR或非門,410,NOT Gate非門,A NOT gate accepts one input value and produces one output value 非門接受一個輸入值，生成一個輸出值。,Figure 4.1 Various representations of a NOT gate,411,NOT Gate非門,By definition, if the input value for a NOT gate is 0, the output value is 1, and if the input value is

8、1, the output is 0 根據(jù)定義，如果非門的輸入值是0，那么輸出值是1；如果輸入值是1，那么輸出值是0. A NOT gate is sometimes referred to as an inverter because it inverts the input value 非門有時候又叫反向器，因為它將對輸入值求反。,412,AND Gate與門,An AND gate accepts two input signals 與門接受兩個輸入信號 If the two input values for an AND gate are both 1, the output is 1

9、; otherwise, the output is 0 如果兩個輸入值全是1，則輸出位1，其它情況均位0.,Figure 4.2 Various representations of an AND gate,413,OR Gate或門,If the two input values are both 0, the output value is 0; otherwise, the output is 1 如果兩個輸入值均為0，則輸出值位0，其它情況的輸出值均為1.,Figure 4.3 Various representations of a OR gate,414,XOR Gate異或門,

10、XOR, or exclusive OR, gate An XOR gate produces 0 if its two inputs are the same, and a 1 otherwise 如果異或門的兩個輸入相同，則輸出0；否則輸出1 Note the difference between the XOR gate and the OR gate; they differ only in one input situation When both input signals are 1, the OR gate produces a 1 and the XOR produces a

11、 0,415,XOR Gate異或門,Figure 4.4 Various representations of an XOR gate,NAND and NOR Gates與非門和或非門,The NAND and NOR gates are essentially the opposite of the AND and OR gates, respectively,Figure 4.5 Various representations of a NAND gate,Figure 4.6 Various representations of a NOR gate,415,417,Review o

12、f Gate Processing門處理回顧,A NOT gate inverts its single input value 非門將對它的唯一輸入值取反。 An AND gate produces 1 if both input values are 1 如果兩個輸入都是1，與門將生成1. An OR gate produces 1 if one or the other or both input values are 1 如果一個輸入值是1，或者兩個輸入都是1，或門將輸出1.,418,Review of Gate Processing門處理回顧,An XOR gate produces

13、 1 if one or the other (but not both) input values are 1 如果只有一個輸入值是1，而不是兩個都是1，異或門將輸出1. A NAND gate produces the opposite results of an AND gate與非門生成的結果和與門生成的相反 A NOR gate produces the opposite results of an OR gate 或非門生成的結果和或門生成的相反,419,Gates with More Inputs具有更多輸入的門,Gates can be designed to accept t

14、hree or more input values 門可以設計成接受三個或更多個輸入值。 A three-input AND gate, for example, produces an output of 1 only if all input values are 1 例如，具有三個輸入值的與門，只有當三個輸入值都是1時，才生成值為1的結果。,Figure 4.7 Various representations of a three-input AND gate,420,Constructing Gates門的構造,Transistor A device that acts, depend

15、ing on the voltage level of an input signal, either as a wire that conducts electricity or as a resistor that blocks the flow of electricity 晶體管根據(jù)輸入信號的電壓電平分為兩種角色，一種是傳導電流的導線，另一種是阻止電流的電阻。 A transistor has no moving parts, yet acts like a switch 雖然晶體管沒有可移動的部分，但是卻可以作為開關 It is made of a semiconductor mat

16、erial, which is neither a particularly good conductor of electricity, such as copper, nor a particularly good insulator, such as rubber 它是由半導體材料制成，所謂半導體材料，就是既不是像銅那樣的良好導體，也不是像橡膠一樣的絕緣體。,421,jasonm: Redo 4.8 (crop),Constructing Gates門的構造,A transistor has three terminals A source源極 A base基極 An emitter,

17、typically connected to a ground wire 發(fā)射極，通常接地 If the electrical signal is grounded, it is allowed to flow through an alternative route to the ground (literally) where it can do no harm,Figure 4.8 The connections of a transistor,422,Constructing Gates門的構造,It turns out that, because the way a transist

18、or works, the easiest gates to create are the NOT, NAND, and NOR gates,Figure 4.9 Constructing gates using transistors,423,Circuits電路,Two general categories In a combinational circuit, the input values explicitly determine the output 組合電路，輸入值明確決定輸出值。 In a sequential circuit, the output is a function

19、 of the input values as well as the existing state of the circuit 時序電路，輸出值是輸入值和電路現(xiàn)有狀態(tài)的函數(shù)。 As with gates, we can describe the operations of entire circuits using three notations Boolean expressions logic diagrams truth tables,424,Combinational Circuits組合電路,Gates are combined into circuits by using th

20、e output of one gate as the input for another 把一個門的輸出作為另一個門的輸入，可以把門組合成電路。,Page 99,425,Combinational Circuits組合電路,Because there are three inputs to this circuit, eight rows are required to describe all possible input combinations This same circuit using Boolean algebra is (AB + AC),Page 100,426,Now l

21、ets go the other way; lets take a Boolean expression and draw,Consider the following Boolean expression A(B + C),Page 100,Page 101,Now compare the final result column in this truth table to the truth table for the previous example They are identical,427,Now lets go the other way; lets take a Boolean

22、 expression and draw,We have therefore just demonstrated circuit equivalence電路等價 That is, both circuits produce the exact same output for each input value combination 對應每個輸入值組合，兩個電路都生成完全相同的輸出。 Boolean algebra allows us to apply provable mathematical principles to help us design logical circuits 布爾代數(shù)

23、允許我們使用已經證明的數(shù)學法則來設計邏輯電路。,428,Properties of Boolean Algebra布爾代數(shù)屬性,Page 101,交換律,結合律,分配律,恒等,余式,429,Adders加法器,At the digital logic level, addition is performed in binary 在數(shù)字邏輯層，加法是用二進制執(zhí)行的。 Addition operations are carried out by special circuits called, appropriately, adders 加法運算是由專用的電路加法器執(zhí)行的。,430,Adders加

24、法器,The result of adding two binary digits could produce a carry value Recall that 1 + 1 = 10 in base two A circuit that computes the sum of two bits and produces the correct carry bit is called a half adder,Page 103,計算兩個數(shù)位的和，并生成正確的進位的電路稱為半加器。,431,Adders加法器,Circuit diagram representing a half adder T

25、wo Boolean expressions: sum = A B carry = AB,Page 103,432,Adders加法器,A circuit called a full adder takes the carry-in value into account 計算兩個數(shù)位的和，并考慮進位輸入的電路叫全加器。,Figure 4.10 A full adder,433,Multiplexers多路復用器,Multiplexer is a general circuit that produces a single output signal 多路復用器是生成單一輸出信號的通用電路 Th

26、e output is equal to one of several input signals to the circuit 輸出值等于該電路的多個輸入值之一 The multiplexer selects which input signal is used as an output signal based on the value represented by a few more input signals, called select signals or select control lines 多路復用器根據(jù)稱為選擇信號或者選擇控制線的輸入信號選擇用哪個輸入信號作為輸出信號,

27、434,Multiplexers多路復用器,The control lines S0, S1, and S2 determine which of eight other input lines (D0 through D7) are routed to the output (F),Figure 4.11 A block diagram of a multiplexer with three select control lines,Page 105,435,Circuits as Memory存儲器電路,Digital circuits can be used to store infor

28、mation 數(shù)字電路可以用來存儲信息 These circuits form a sequential circuit, because the output of the circuit is also used as input to the circuit 這些電路是時序電路，因為這種電路的輸出信號也被用作電路的輸入信號,436,Circuits as Memory存儲器電路,An S-R latch stores a single binary digit (1 or 0) S-R鎖存器存儲一個二進制位 There are several ways an S-R latch circuit could be designed using various kinds of gates,Figure 4.12 An S-R latch,437,Circuits as Memory存儲器電路,The design of this circuit guarantees that the two outputs X and Y are always complements of each other The value of X at any point in time is considered to be the curre