数字电子技术(课件)lec22.ppt

1、2020/7/13,Chapter 9 Shift Registers,1,Lecture 22 Outline,9-6Bidirectional Shift Registers 9-7Shift Register Counters 9-8Shift Register Applications Quiz 2,Lecture 22: Shift Registers Applications,2020/7/13,Chapter 9 Shift Registers,2,Key Knowledge in Lecture 22,Operation principle of bidirectional s

2、hift register. Johnson counter circuits and their sequences. Ring counter characteristics. Use of 74HC195 as a ring counter and Johnson counter. Analysis of 74HC195 as a regular counter. Some other applications of shift register.,Difficult Topics: Determine shift register counting pattern b) in 1 us

3、; c) In the propagation delay time of eight flip-flops; d) In the propagation delay time of one flip-flop.,Answer: d),With a 100kHz clock frequency, eight bits can be serially entered into a shift register in 80 us;b) 8 us; c) 80 ms; d) 10 us,Answer: a),Lecture 22: Shift Registers Applications,2020/

4、7/13,Chapter 9 Shift Registers,26,Test Your Understanding,3.A modulus-10 Johnson counter requires a) ten flip-flops; b) four flip-flops c) five flip-flops;d) twelve flip-flops,Answer: c),4.A modulus-10 ring counter requires a minimum of : a) ten flip-flops;b) five flip-flops; c) four flip-flops; d)

5、twelve flip-flops;,Answer: a),Lecture 22: Shift Registers Applications,5.When an 8-bit serial in/serial out shift register is used for a 24 us time delay, the clock frequency must be a) 41.67 kHz; b) 333 kHz; c) 125 kHz; d) 8 MHz,Answer: b),2020/7/13,Chapter 9 Shift Registers,27,Summary of Lecture 2

6、2,Some of the bidirectional shift registers have two separate serial inputs while others only have one. An n stage Johnson counter produces a modulus of 2n sequence; A ring counter can only produce n sequences. 74HC195 can be connected as a ring counter and a Johnson counter fairly easily. 74HC195 c

7、an be connected as counters of any modulus depend on the parallel load data. For example, the parallel data is 0, the modulus is 12. One of the application for the shift register is in the binary-to-BCD converter where binary number is shifted in serially and changed to BCD.,Lecture 22: Shift Registers Applications,2020/7/13,Chapter 9 Shift Registers,28,Thank you for your participation!,The End of Lecture 22,Lecture 22: Shift Registers Applications,2020/7/13,Chapter 9 Shift Registers,29,Two way interactive question-and-answer session.,Home