【正文】 50%10%B a s e l i n eP u l s e w i d t hR i s e t i m e F a l l t i m eA m p l i t u d etWtrtfU n d e r s h o o tR i n g i n gOv e r s h o o tR i n g i n gD r o o pFundamentals of Digital Circuits 28 Digital waveform haracteristics ? Periodic pulse Period=T=T1= ? ? ? =Tn Frequency=1/T ? Nonperiodic pulse T1 T2 T3 T4 …… fTTf1,1??Fundamentals of Digital Circuits 29 Period Pulse The Duty cycle (D ) is defined as the ratio of the pulse width (tw ) to the period (T ) and can be expressed as a percentage. . %100 ??Ttc y c l eD ut y w T tw 0 1 10 11 t (ms) Fundamentals of Digital Circuits 30 Example 11: A portion of a periodic digital waveform is shown in the figure. The measurements are in milliseconds. Determine the following: (1)period (2)frequency (3) duty cycle Solution: (1) T=10 ms (2) f=1/T=1/10ms=1/=100Hz (3) Duty cycle=tw/T=1ms/10ms?100%=10% T tw 0 1 10 11 t (ms) Fundamentals of Digital Circuits 31 A Digital Waveform Carries Binary Information ? When the waveform is HIGH, a binary 1 is present。Fundamentals of Digital Circuits 1 Digital Fundamentals Tenth Edition Floyd 169。 2022 Pearson Education Fundamentals of Digital Circuits 2 ? Remended:清華大學(xué)電子學(xué)教研組編，閻石主編，數(shù)字電子技術(shù)基礎(chǔ)，第四版，高等教育出版社， 7040066963 ? Remended:王毓銀主編，數(shù)字電路邏輯設(shè)計(jì)（脈沖與數(shù)字電路，第三版），高等教育出版社， 7040077302 Fundamentals of Digital Circuits 3 數(shù)字電子技術(shù)基礎(chǔ) Fundamentals of Digital Circuits 4 數(shù)字電路邏輯設(shè)計(jì) Fundamentals of Digital Circuits 5 Chapter 1 Introductory Concepts Fundamentals of Digital Circuits 6 What is Digital? How does digital signal work? Why use Digital? Digital Fundamentals of Digital Circuits 7 What is Digital? Digital Analog Fundamentals of Digital Circuits 8 Digital and Analog signals(quantity) ? Analog signals ? Continues in time domain ? Continues values . Speaker, Thermometer Temperature (oC) Time(s) 0 Fundamentals of Digital Circuits 9 Sampled signals Temperrature 0c Temperature (oC) Time(s) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ? Discrete in time domain ? Continues values Fundamentals of Digital Circuits 10 Most natural quantities that we see are analog and vary continuously. Analog systems can generally handle higher power than digital systems. Digital systems can process, store, and transmit data more efficiently but can only assign discrete values to each point. Analog Quantities 1100A . M .95908580752 3 4 5 6 7 8 9 10 1 1 12 1 2 3 4 5 6 7 8 9 10 1 1 12P . M .T e m pe ra t ur e( 176。 when the waveform is LOW, a binary 0 is present. Each bits in a sequence occupies a defined time interval called a bit time, or bit interval. Clock 1 0 Fundamentals of Digital Circuits 32 The Clock ? In digital systems, all digital waveforms are synchronized with a basic timing waveform, called the clock. The clock is a periodic waveform. The clock waveform itself does not carry information. Fundamentals of Digital Circuits 33 The Clock ? In digital systems, all digital waveforms are synchronized with a basic timing waveform, called the clock. Fundamentals of Digital Circuits 34 A timing diagram is used to show the relationship between two or more digital waveforms, Summary Timing Diagrams C l oc kABCA diagram like this can be observed directly on a logic analyzer. Fundamentals of Digital Circuits 35 Data can be transmitted by either serial transfer or parallel transfer. Summary Serial and Parallel Data C o m p u t e r M o d e m1 0 1 1 0 0 1 0t0 t1 t2 t3 t 4 t 5 t 6 t 7C o m p u t e r P r i n t e r0t0t11001101Fundamentals of Digital Circuits 36 13 BASIC LOGIC OPERATIONS Fundamentals of Digital Circuits 37 Logic Functions ? For example, the propositional statement “The light is on” will be true if the “The bulb is not burned out” is true and if “The switch is on” is true. ? The first statement is then the basic proposition, and the other two statements are the conditions on which the proposition depends. Fundamentals of Digital Circuits 38 Boolean Algebra ? In 1850s, the Irish logician and mathematician Gee Bool developed a mathematical system for formulating logic statements with symbols so that problems can be written and solved in a manner similar to ordinary algebra. Fundamentals of Digital Circuits 39 Basic Logic Operations ? In Boolean algebra, there are three basic logic operations: NOT, AND, and OR. ? Each of the