Digital electronics by malvino and leach pdf download






















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These cookies do not store any personal information. Skip to content. This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Privacy Overview This website uses cookies to improve your experience while you navigate through the website. Privacy Overview. Necessary Always Enabled. For instance, the symbol in Fig. This is still an inverter, but the circle on the input side has additional significance, which will be considered next.

The Tri-state Inverter A tri-state inverter is easy to construct, as shown in Fig. When G is high, the enable switch opens, and the output is disconnected from the inverter. The standard logic symbol for this tri-state inverter is given in Fig. The inverting amplifier symbol indicates that v;, is the inverse of v; the small circle is at the amplifier output.

However, note the. From the truth table, you cari. Thus, when G is low, the circuit is activated and output v;, is the inverse of the input v;. Compare this with the G input to the tri-state buffer in Fig. In this case, the switch is closed and the circuit is activated when G is high.

The inputs to this gate are labeled V1, V2, V,, The operation of an AND gate can be expressed in a number of different, but equivalent, ways. For instance. If any input is low, i,:, will be low. AND 3. A model for an AND gate having 2 inputs is shown in Fig. This gate can be used to make "logical" decisions; for example, "If V1 and V2 , then 11;,.

This can be expressed in the form of a logic equation written as. The operation is summarized in the truth table in Fig. The symbol for a 2-input AND gate is shown in Fig. Thus, AND is a logic operation which is realized here through a logic gate. The inputs to this gate are labeled V1, V2 , V,, V", there are n inputs , and the output is labeled V: The operation of an OR gate can be expressed in a number of different ways. For instance, 1.

V: will be low only when all inputs are low. V0 OR 2. If any input is high, V: will be high. This gate can be used to make "logical" decisions; for example, "If V1 or V2, then v;,. The symbol for a 2-input OR gate is shown in Fig. Thus, OR is a logic operation which is realized here through a logic gate. Refer only to the tri-state buffer symbol in Fig. Check your response with the truth table in Fig. Repeat if both G and v; are high. Refer only to the inVertingtri-state buffer symbol in Fig.

For the AND gate in Fig. What is the state of V,,? If the AND gate in Fig. If the ORgate in Fig. Memory Elements A digital memory element is a device or perhaps a circuit that will maintain a desired logic level at its output till it is changed by changing the input condition. The simplest memory element is the switch shown in Figs. The switch in Fig. It is easy to see that this switch can be used to store a digital level, and it will remember the stored level indefinitely. The simplest electronic circuit used as a memory element is called a flip:flop.

Since a flip- flop is constructed using transistors, its operation depends upon de supply voltage s as seen in Fig. The flip-flop can be used to store a logic level high or low , and it will retain a stored level indefinitely provided the de supply voltage is maintained. An interruption in the de supply voltage will result in loss of the stored logic level.

When power is first applied to a flip-flop turning the system on first thing in the morning , it will store either a high or a low. This is a "random" result, and it must be accounted for in any digital system.

The output labeled A is simply the inverse of A. Here's how it works: 1. To summarize, when the flip-flop is SET, it stores a high a logic 1. A simple flip-flop such as this is often called a latch, since its operation is similar to a switch. Registers A group of flip-flops can be connected together to store more than a single logic level. For instance, the four flip-flops in Fig. As such, they could be used to store any of the ten binary numbers given in Table 1.

When we speak of decimal numbers, each position in a num- ber is called a decimal digit, or simply a digit. For example, the decimal number has three digits. When we speak of binary numbers, each position in the number is called a binary digit, or R bit. The term "binary digi! The four flip-flops in Fig. A group of flip-flops used to store a binary number is called a register, or sometimes a storage register.

The register in Fig. There are eight flip-flops in an 8-bit reg- ister, and so on. In the TTL family, the is an 8-bit regis- ter. In general, binary numbers such as A four-bit register this are referred to as data. A register is a fundamental building block in a microprocessor or digital computer, and you can now see the beginnings of how these systems are used for computation. It is constructed using eight flip-flops and some additional electronic circuits.

A binary number is stored in this register by applying the appropriate level high or low at each input simultaneously. Thus one bit is "shifted" into each flip-flop in the register. The binary number is said to be shifted into the register in parallel, since all bits are entered at the same time. In this case, the binary number or data is entered in one single operation. Once a number is stored in this register, it appears immediately at the 8 outputs, a through h.

A is an example of an 8-bit parallel register. It is also constructed using eight flip-flops and some additional electronic circuits. It will store an 8-bit binary number, but the number must be entered into the register one bit at a time at the input. It thus requires eight operations to store an 8-bit number. This is how it is done. The first bit of the binary number is entered in flip-flop A at the input.

Outputs a b. This shift right process is repeated, and after eight operations, the 8-bit number will be stored in the register. Since the bits are entered one after the other in a serial fashion, this is called a serial register. For a stored number to be extracted from this register, the bits must he shifted through the flip-flops from left to right. The stored number will then appear at the output, one bit at a time.

It requires eight operations, or eight right shifts, to extract the stored number. A TTL is an example ofan 8-bit serial register this particular IC also provides parallel outputs. Transferring Digital Data A register is used to enter data binary numbers into a microprocessor or computer.

A register is also used to extract data from a computer and direct it to an external destination. Wire cables are generally the means for connecting systems. If a parallel register is used, the data is said to be shifted in parallel.

The connector in this case must have one pin for each bit, and the cable must have at least one wire for each bit. An 8-bit register requires a cable having at least 8 wires, a bit register must have at least 16 wires, and so on. Data are also transferred shifted between registers within a digital system.

Instead of drawing all 8 or 16 or 32 wires on a schematic, it is common practice to use an arrow between the registers, as illustrated in Fig. The number 8 in parentheses means that there are eight wires. In this case, there are eight connections used to transfer 8 bits of data in parallel from register A to register B. The eight wires represented by this arrow are called a data bus. The double arrow shown in Fig. This is a bit bidirectional data bus.

On the other hand, data can be shifted serially into or out of a serial register, and only one wire connection is required for the data. Clearly, parallel operation will transfer data into or out of a computer system much more rapidly than serial operation. The price paid for this gain in speed is an increase in complexity, in terms of both the electronic circuits and the increased number of connections wires in the cable.

The computer connector where data is entered or extracted is frequently called a port. Nearly all computer systems have available both a serial port and a parallel port. Magnetic and Optical Memory Any memory element must be capable of storing or retaining only two logic levels, and there are numerous devices with the appropriate electronic circuits used for this purpose.

One of the most common systems for memory makes use of the fact that a magnetic material can be magnetized with two different orientations. Thus, magnetizing spots on a strip of magnetic tape, or on a hard disk with a magnetic coating, or on a magnetic floppy disk are well known and widely used memory systems. In optical memory data is encoded in binary by making two different kinds of reflecting surface on a spiral track of a circular disk.

A special pointed source of light falls on the surface and intensity of reflected light gives infonnation about the data stored.

A number of devices that utilize magnetic and optical storage are illustrated in Fig. Look at the binary representation of the decimal number 9 in Table 1. L How many bits are there in this binary number? If it is stored in the register in Fig. If a shift operation requires a time of J s to complete, bow long would it take to enter an 8-bit number into the parallel register in Fig.

How long would it take to enter an 8,bit number into the serial register in Fig. When we speak of a microprocessor, what is meant by the term port? Counters It was mentioned previously that counting is an operation easily performed by a digital circuit. A digital circuit designed to keep track of a number of events, or to count, is called a counte,: The counter in Fig.

It is similar to a storage register, since it is capable of storing a binary number. The input to this counter is the rectangular waveform labeled clock. Each time the clock signal changes state from low to high, the counter will add one 1 to the number stored in its flip-flops.

In other words, this counter will count the number of clock transitions from low to high. A clock having a small circle bubble in the input side would count clock transitions from high to low.

As an example of how this circuit might be used, suppose that the counter consists of four flip-flops, all of which are RESET. That is, the binary number stored in the counter is The clock signal is initially held low.

Now the clock is allowed to "run" for six clock periods, and then it is held low, as shown in Fig. After the first clock transition from low to high, the counter will advance to I. After the second transition, it will advance to , and so on, until it will store the binary number Oll O after the sixth transition. The binary number Oll O is equal to decimal 6, and thus the counter has counted and stored the six clock transitions!

A four-flip-flop counter can count decimal numbers from Oto To count higher, it is necessary to add more flip-flops. The tenn 2" means 2 raised to the nth power, that is, 2 multiplied by itself n times. For now, this listing of powers of2 can be used with Eq. Solution From Eq. Arithmetic logic Unit An arithmetic logic unit ALU is a digital circuit capable ofperfonning both arithmetic and logic operations.

Multiplication x and division 7 of digital numbers are accomplished with other digital circuits. The ALU represented in Fig.

A bus and the B bus, and the F bus is the resultant output. The digital levels on the S bus detennine which operation is to be performed. Generally, each of the data buses will have the same number of bits. Both the A and B inputs are 4-bit buses, and the output at F is also F a 4-bit bus. For this particular circuit, the control signal at the S bus is also four bits.

In addition, the has a number of other inputs and outputs which we will discuss in detail later. The two numbers to be added are represented by the proper logic levels at A and B, and the SUM of these two numbers will appear at output F. Here's how we might do it with decimal numbers. The digital levels illustrated in Fig. The equivalent decimal numbers are shown in parentheses. The desired function appears at the F bus. There are tour AND operations.

Comparison Comparing the magnitude of two numbers is an important logical operation. The circuit in Fig. The other two outputs will be low. A in the TTL family is a 4-bit comparator similar to Fig. Also, the ALU can be used with the same results. A comparator. In the case of a computer, information is frequently entered by typing on a keyboard or perhaps by using a magnetic floppy disk.

Useful information can be obtained from the computer by examining the visual displays on a cathode-ray tube CRT or by reading material produced on a printer. Clearly there is a requirement to connect multiple input devices, one at a time, to the system. The digital circuit used for this operation is a multiplexer. Likewise, there is a need to connect the system output to a number of different destinations, one at a time.

The digital circuit used for this purpose is a demultiplexer. The term multiplex means "many into one. There are n input lines. Each line is used to shift digital data serially. There is a single output line which is connected to the computer system input port. Operation of the circuit can be explained by using the "switch" as a model. Each setting of the digital control levels on the C bus will connect the switch to one of the input lines.

Data from that particular input is then entered into the computer. Changing the C bus levels will connect a different input. Thus, data from multiple sources can be connected to a single input port, one at a time. It has 16 input lines and a single output line.

The opposite of multiplex is demultiplex, which means "one into many. This digital circuit simply connects the single data input line to one of the n output lines, one at a time, according to the levels on the C bus. Thus serial data from the computer output port can be directed to different destinations, one at a time. Any information entered into a digital system must be in the form of a digital number.

A circuit that changes data into the required digital form is called an encoder. The encoder shown in Fig. It may be used with a keyboard. For instance, depressing the number 4 key on a keyboard will cause input line 4 to this encoder to be high the other inputs are all low. The result will be decimal 4, binary , at the encoder output as shown. Taking digital information from the output of a computer and changing it into another form is accomplished with a decoder, for example, changing the digital number O decimal 6 into its decimal fonn.

The decoder in Fig. As shown, the binary input OI IO will cause output line 6 to be high, while all other output lines remain low. There are many different types of encoders and decoders. A number of them will be discussed in detail in Chapter 4.

What binary number will be stored in the counter in Fig. How many flip-flops are required to construct a digital counter capable of counting events? State whether or not the ALU in Fig. What are the digital output levels of the encoder in Fig.

A computer intended to perform a very specific task, constructed with a minimum number of components, might be referred to as a microcomputer.

Small portable, or desktop, computers are usually in the microcomputer class. Computers with greater capacities, often used in business, are called minicomputers. A large mainframe computer system capable of storing and manipulating massive quantities of data, for example, a digital computer system used by a bank or an insurance company, might then be called a maxicomputer. Uses What can a digital computer be used for?

Numerical computation is surely one possible use. The inclusion of an ALU with additional logic circuits provides arithmetic capabilities addition, subtraction, multiplication, division. The logic portion of the ALU means the computer can be used to make logical decisions. Beyond these basic functions, a digital computer can be used to process data balance bank accounts , to rapidly perform otherwise time-consuming tasks determine payroll amounts and print out paychecks , to precisely monitor and control intricate processes life support systems in a hospital operating room , to use speech for communication with humans automatic telephone systems and voice recognition -the list is almost end- less, and is limited only by the ingenuity and resourcefulness of individual users!

Basic Configurations A microcomputer designed to control a given machine, process, or system might be represented as in Fig. The control signals produced by the computer appear as the output bus and are sent to an output device. Here, the signals are properly conditioned and sent to the mechanism being controlled. The controlled entity must then send signals indicating its present condition back to the computer via an input device and via the input bus. The computer analyzes these present condition signals, determines any necessary action, and sends required correction signals out to the system.

A microcomputer system might be designed to irrigate the lawn area of a park. Watering is to be done only at night, when the soil moisture falls below a given value.

The system "sensors" in this case would be 1 a probe to detect soil moisture and 2 a light detector to distinguish between daylight Controlled IA and darkness. The input bus is serviced with A digital computer based system aMUX. Audio output. This allows the connection of a number of different input devices: A keyboard for typewritten entry of alphanumeric information A disk drive or tape drive for entering data stored in magnetic form A microphone for voice input The DEMUX on the output bus allows numerous possibilities for receiving information from the computer: The familiar CRT for a visual display A printer to provide printed material called hard copy A disk or tape drive to record data in magnetic form Perhaps a speaker for audio information A minicomputer such as this can be used for many different tasks.

It can be used as a word processor, for data processing, for communication via telephone both voice and fax , for training in an educational setting, for computer games, and so on! The block diagram in Fig. For instance, a maxicomputer will likely have more than one printer, and perhaps even different types of printers. It will generally have a large number of users, all of whom desire access to the system at the same time.

One workstation must then be provided for each user. A keyboard and a CRT are the minimum components required at each workstation. The digital circuits used to construct maxicomputer systems are necessarily more complicated than minicomputer systems, and they may operate at a much faster rate. Let's take a look inside a typical digital computer. It is constructed using an ALU along with a number of registers and counters.

All the operations within the CPU, and indeed within the computer itself, must be Clock carefully coordinated. A digital signal refened to as the system clock is used as a reference to time when specific operations take place. The clock signal is usually a periodic, rectangular waveform as illustrated CPU in Fig.

Using a crystal in the clock circuit allows the accuracy and stability of the clock frequency, to The "heart" and "brain" of be controlled with great precision.

The clock provides a digital computer a "heartbeat" for the computer. A block diagram of a digital computer is started by drawing the CPU and clock as shown in Fig. The CPU is capable of computation and decision, but it must have specific instructions telling it exactly what to do and when to do it.

This set of instructions is called a program. A program is a detailed list of CPU operations written by a human programmer. The pro- grammer decides what the computer is to do and when it should be done, and then writes a list of instructions to be carried out in the proper order. The program is Program Data entered into the computer, using perhaps a keyboard, memory memory and stored in the computer memory.

It will execute the instruction and then fetch the next instruction. With this repeated fetch- and-execute cycle, the CPU will accomplish the desired task. A memory block used. A portion of the memory block in Fig.

This is the area where the information being processed by the computer is stored. Since the CPU takes "reads" data from memory, as well as returns "writes" data into memory, the memory data bus is bidirectional.

By contrast, the program data bus is not bidirectional, since information on this bus is always from memory to CPU. The CPU communicates with the "outside world" by means of the input encoders and the output decoders.

This configuration is sometimes quite inefficient, since all information entering or exiting the computer must pass through the CPU. The CPU operates at a much faster rate than most external devices, and it must wait while data are being entered or exited: A direct memory access DMA block is generally included to alleviate this problem.

As seen in Fig. While information is being transfened via the DMA, the CPU is free to cany on its computational or logical operations. This greatly improves system efficiency as well as speed of operation. Before data can be entered into the computer, a signal on the input requestline asks the computer for "per- mission" to input information. For instance, depressing the enter key on a keyboard will generate an input request signal.

Program Data memory memory. This request-acknowledge sequence is often called handshaking. A similar handshaking must occur when the CPU is ready to deliver data to an external device.

However, in this case, the CPU makes an output request, and the external device gives permission. All of these blocks are operated in synchronism with the clock, but additional direction must be provided. These online bookshops told us they have this item: The University of Sydney. Skip to content Skip to search. Not open to the public Author Malvino, Albert Paul. Language English Dewey Number This single location in New South Wales: Other suppliers National Library of Australia — Copies Direct The National Library may be able to supply you with a photocopy or electronic copy of all or part of this item, for a fee, depending on copyright restrictions.

Electronic digital computers — Circuits. Public Private login e. Not open to the public Book; Illustrated English Show 0 more libraries Then set up a personal list of libraries from your profile page by clicking on your user name at the top right of any screen. We were unable to find this edition in any bookshop we are able digitsl search. To include a comma in your tag, surround the tag with double quotes. You also may like to try some of these bookshopswhich may or may not sell this item.

Not open to the public Book; Illustrated English Show 0 more libraries Then set up a personal list of libraries from your profile page by clicking on your user name at the top right of any screen. These 7 locations in All: Skip to content Skip to search. Electronic digital computers — Circuits. To include a comma in your tag, surround the tag with double quotes. Other Authors Leach, Donald P. In order to set up a list of libraries that you have access to, you must first login or sign up.

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