Introduction to Digital Electronics Technology

Introduction to Digital Electronic Technology
1.1 Overview
1.1.1 Digital Signals and Digital Circuits
1. Digital Signals and Analog Signals
2. Analog Circuits and Digital Circuits
1.1.2 Classification of Digital Circuits
1. Classification by Circuit Type
2. Classification by Integration Level
3. Classification by Semiconductor Conductive Type
1.1.3 Advantages of Digital Circuits
1. Easy Integration
2. Strong Anti-interference Capability, High Reliability
3. Convenient for Long-term Storage
4. Strong Versatility, Low Cost, and Multiple Series
5. Good Confidentiality
1.1.4 Main Parameters of Pulse Waveform
1. Pulse Amplitude Um
2. Pulse Rise Time
3. Pulse Fall Time
4. Pulse Width 5.
Pulse Period
6. Pulse Frequency
7. Duty Cycle q

1.2 Number systems and code systems
1.2.1 Number systems
1. Decimal 2. Binary 3. Octal and hexadecimal 1.2.2 Conversion between different number systems 1. Conversion of various number systems to decimal 2. Conversion of decimal to binary 3. Conversion between binary, octal and hexadecimal
1.2.3 Binary codes 1. Binary-decimal codes 8421, 5421 and remainder 3 codes 2. Reliability codes 1. Gray code 2. Parity check code Homework: P10 2. (1) (3) 3. (1) (3) 4. (4) 5. (4) 6. (4) 7. (4) Chapter 1 Introduction

1.1 Overview
1.1.1 Digital Signals and Digital Circuits
Electrical signal - current or voltage that changes with time.
1. Digital Signals and Analog Signals Analog
signal - the amplitude changes continuously with time
Digital signal - intermittent change (discrete change), discrete in time and integer in amplitude, mostly composed of two values ​​0 and 1, also known as binary signal.
For example, P1 Figure 1.1.1. Discuss discrete signals with classmates.

2. Analog circuits and digital circuits
Analog circuits - Circuits that transmit or process analog signals, such as voltage, power amplification, etc.;
digital circuits - Circuits that process, transmit, store, control, process, calculate, operate, and perform logical operations on digital signals.
For example, measuring motor speed: motor-photoelectric conversion-shaping-gate control-counter-decoder-display
Time base circuit
1.1.2 Classification of digital circuits The
rapid development of microelectronics technology has led to the rapid development of digital circuits.
1. Classification by circuit type
(1) The output of a combinational logic circuit is only related to the input at the time, such as encoders, adders and subtractors, comparators, and data selectors.
(2) The output of a sequential logic circuit is not only related to the input at the time, but also to the original state of the circuit.
For example, triggers, counters, registers
2. Classification by integration level
SSI →MSI→LIS→VLSI

Table 1.1.1 Classification of digital integrated circuits

3. Classification by the conductivity type of semiconductors
(1) Bipolar circuit
(2) Unipolar circuit

1.1.3 Advantages of digital circuits
1. Easy to integrate. Two states "0" and "1", low requirements for component precision.
2. Strong anti-interference ability and high reliability. The signal is easy to distinguish and not easily disturbed by noise.
3. Convenient for long-term storage. Floppy disk, hard disk, CD.
4. High versatility, low cost, and many series.
(International standard) TTL series digital circuits, gate arrays, programmable logic devices.
5. Good confidentiality. Easy to encrypt.

1.1.4 Main parameters of pulse waveform
In digital circuits, pulse waveforms are processed and handled, and the most commonly used is rectangular pulse.
Figure 1.1.2 Parameters of pulse waveform

1. Pulse amplitude. The maximum value of the pulse voltage waveform change, in volts (V).
2. Pulse rise time. The time required for the pulse waveform to rise from 0.1Um to 0.9Um.
3. Pulse fall time. The time required for the pulse waveform to fall from 0.9Um to 0.1Um.
The shorter the pulse rise time tr and fall time tf, the closer it is to the ideal short pulse. The units are seconds (s), milliseconds (ms), microseconds (us), and nanoseconds (ns).
4. Pulse width. The time required for the pulse to rise from 0.5Um to fall from 0.5Um, the unit is the same as tr and tf.

5. Pulse period T. In a periodic pulse, the time required for two adjacent pulse waveforms to repeat. The unit is the same as tr and tf.
6. Pulse frequency f: The number of times a pulse appears per second. The unit is Hertz (Hz), kilohertz (kHz), megahertz (MHz), f = 1∕T.
7. Duty cycle q: The ratio of pulse width to pulse repetition period T. q = ∕T.
It is a parameter that describes the density of the pulse waveform.

1.2 Number system and code system
1.2.1 Number system 1.
Decimal system
1. Representation


Discuss with classmates the representation methods and characteristics of binary, octal and hexadecimal systems

2. Binary

3. Octal and Hexadecimal
1. Octal
Every eight is incremented; coefficients are 0 to 7; base 8; power 8n.
2. Hexadecimal
Every sixteen is incremented; coefficients are: 0 to 9, A, B, C, D, E, F; base 16; power 16n.

Table 1.2.1 Decimal, binary, octal, hexadecimal comparison table

1.2.2 Conversion between different number systems 1. Conversion of
various number systems into
decimal When converting binary, octal, and hexadecimal numbers into decimal, just expand them by weight and find the sum of each weighted coefficient to get the decimal number corresponding to the corresponding number.
Example:

2. Decimal to Binary Conversion
The integer part of a decimal number is converted to a binary number using the "divide by 2 and take the remainder method";
the decimal fraction part is converted to a binary number using the "multiply by 2 and take the integer method".
Example 1.1.1 Convert the decimal number (107.625)10 to a binary number.
The integer part of a decimal number is converted to a binary number using the "divide by 2 and take the remainder method", which is to divide the integer part by 2 successively and write down the remainders in sequence until the quotient is 0. The first remainder is the lowest bit of the binary number, and the last remainder is the highest bit.
Solution: ① Integer part conversion


Therefore,
② Decimal part conversion The
decimal fraction part is converted to a binary number using the "multiply by 2 and take the integer method", which is to multiply the decimal part by 2 continuously and take the integer part of the multiplier as the decimal of the binary number.
Therefore, the binary number corresponding to the decimal number (107.625)10 is
(107.625)10＝(1101011.101)2

3. Conversion between binary, octal and hexadecimal
1. Conversion between binary and octal
(1) Convert binary numbers to octal numbers.
The method of converting binary numbers to octal numbers is: the integer part starts from the low bit, and every three binary numbers form a group. If the last three digits are less than three, add 0 to the high bit to make up to three digits; the binary number after the decimal point starts from the high bit, and every three binary numbers form a group. If the last three digits are less than three, add 0 to the low bit to make up to three digits, and then replace them with the corresponding octal number, and then write the corresponding octal number in order.
Example 1.1.2 Convert the binary number (11100101.11101011)2 to octal number.
(11100101.11101011)2 = (345.726)8

(2) Convert an octal number to a binary number.
Replace each octal number with three binary numbers and arrange them in the original order to get the corresponding binary number.
Example 1.1.3 Convert the octal number (745.361)8 to binary.
(745.361)8 = (111100101.011110001)2

2. Conversion between binary and hexadecimal
(1) Convert binary numbers to hexadecimal numbers.
The method of converting binary numbers to hexadecimal numbers is: the integer part starts from the low bit, and each four binary digits form a group. If the last digit is less than four digits, add 0 to the high bit to make up four digits; the decimal part starts from the high bit, and each four binary digits form a group. If the last digit is less than four digits, add 0 to the low bit to make up four digits, and then replace it with the corresponding hexadecimal number, and then write the corresponding hexadecimal number in order.
Example 1.1.4 Convert the binary number (10011111011.111011)2 to hexadecimal number.
(10011111011.111011)2 = (4FB.EC)16

(2) Convert hexadecimal numbers to binary numbers.
Replace each hexadecimal digit with four binary digits and arrange them in the original order to get the corresponding binary number.
Example 1.1.5 Convert the hexadecimal number (3BE5.97D)16 to binary.
(3BE5.97D)16 = (11101111100101.100101111101)2

1.2.3 Binary code
Discussion: The role of code; BCD code.
1. Binary-decimal code
The code that represents the ten digits 0 to 9 of a decimal number with binary numbers is called binary-decimal code, also known as BCD code.

Table 1.2.2 Commonly used binary-decimal code table (focusing on 8421 code, 5421 code and remainder 3 code)

Note: The meaning of the weight code is included.

2. Reliability Code
1. Gray Code

Table 1.2.3 Gray code and binary code relationship comparison table

2. Parity check code
In order to detect and correct errors and improve the anti-interference ability of the equipment, reliability codes need to be used. Parity check codes have the ability to check such errors. They are composed of two parts.

Table 1.2.4 8421 parity check code