INC 253 Digital and electronics laboratory I Laboratory 9 Sequential Circuit Author: ID Co-Authors: 1. ID 2. ID 3. ID Experiment Date: Report received Date: Comments For Instructor Full Marks Pre lab 10 Results 15 Discussion 25 uestions 10 Conclusion 5 Total 65 Department of Control System and Instrumentation Engineering Faculty of Engineering ing Mongkut s University of Technology Thonburi
Objectives 1. To study the functions of asynchronous and synchronous counter circuit. 2. To understand how to make the count-up and count-down asynchronous and synchronous counter circuit. 3. To study the functions of shift register circuit. 4. To understand how to make shift register circuit. Equipments Required 1. Training Board Devices Required 1. IC no. 7408, 7474, 7476 Basic Information 1. Asynchronous Counter Asynchronous counter is a counter circuit, which created from the series of - flip-flops. The clock signal will be given to the clock input of the first - flip-flop then the output of the first - flip-flop will connect to the input of the adjacent flip-flop. The output signal, which represents the current binary counting value, is the output signal ( ) of all - flip-flop. While the output ( ) of the first - flip-flop is the least significant bit (LSB) of the binary value. The maximum number of counting value depends on the number of - flip-flops in the circuit. For example, the 4 bits counter is composed of 4 - flip-flops. This maximum number, which this counter can count, is 2 4 = 16. Hence, this counter can count from 0 to 15. If the output ( ) of the first - flip-flop is connected to the clock input of the adjacent - flip-flop, this counter will be the count-up counter. For example, the connecting of flip-flops in Fig. 1 is 4-bits count-up asynchronous counter. A B C D CL All and connect to Fig. 1: 4-bits count-up asynchronous counter INC, MUTT 2
However, if the output ( ) of the first - flip-flop is connected to the clock input of the adjacent - flip-flop, this counter will be the count-down counter, as shown in Fig. 2. A B C D CL All and connect to 2. Synchronous Counter Fig. 2: 4-bits count-down asynchronous counter Synchronous counter was created for figure out the problem of counter circuit, which contains a lot of bits for counting. In this case, if we use asynchronous counter, it will consume a lot of time to complete one counting. Since the adjacent counter need to wait the previous counter to complete the counting first, before receiving the output signal for counting and sending the output signal to the next flip-flop. The synchronous counter, as shown in Fig. 3, was designed by parallel connecting the input signal to the clock input of each flip-flops. The maximum number of counting value depends on the number of flip-flops in the circuit, which equals to 2 n (where n is the number of flipflops in the circuit). A B C D CL input 3. Shift Register Circuit Fig. 3: 4-bits count-up synchronous counter Shift register circuit is widely used in the internal circuit of computers, calculators and printers. The shift register will be used as buffer for transfer data in and out, and can be used for both serial and parallel data transfer. The shift register circuit can be created from the connection of D flop-flops or - flip-flops. One flip-flop is used for represent 1 bit of data. INC, MUTT 3
Pre-Lab Preparation 1. Design the 3-bits count-up asynchronous counter circuit by using IC7476 and plot its timing diagram when outputs start at 0000. INC, MUTT 4
2. Design the 3-bits count-up asynchronous counter circuit by using IC7476 and plot its counter output signals when outputs start at 0000. INC, MUTT 5
3. Plot the counter output signals of the 3-bits count-up synchronous counter circuit in Fig. 4 when outputs start at 0000. INC, MUTT 6
4. Plot the counter output signals of the Mod-5 synchronous counter circuit in Fig. 5 when outputs start at 0000. INC, MUTT 7
5. Plot the D flip-flop output signals of the Shift Register circuit in Fig. 6 when outputs start at 0000. INC, MUTT 8
Procedure 1. Asynchronous Counter 1.1. Make the 3-bits count-up asynchronous counter circuit by using IC 7476. 1.2. Put each pulse of input signal to the counter circuit and notice the changing of output signal from these 3 flip-flops. 1.3. Record the result in Table 1. Table 1: The result the 3-bits count-up asynchronous counter. Input signal Output signal Clock No. C B A Decade code 1 2 3 4 5 6 7 8 9 10 1.4. Make the 3-bits count-down asynchronous counter circuit by using IC 7476. 1.5. Put each pulse of input signal to the counter circuit and notice the changing of output signal from these 3 flip-flops. 1.6. Record the result in Table 2. INC, MUTT 9
Table 2: The result the 3-bits count-down asynchronous counter. Input signal Output signal Clock No. C B A Decade code 1 2 3 4 5 6 7 8 9 10 2. Synchronous Counter 2.1. Make the 3-bits count-up synchronous counter circuit by using IC 7476, as shown in Fig. 4 (connect logic 1 to the and input of the first flip-flop). A B C CL input Fig. 4: 3-bits count-up synchronous counter INC, MUTT 10
2.2. Put each pulse of input signal to the counter circuit and notice the changing of output signal from these 3 flip-flops. 2.3. Record the result in Table 3. Table 3: The result the 3-bits count-up synchronous counter. Input signal Output signal Clock No. C B A Decade code 1 2 3 4 5 6 7 8 9 10 2.4. Make the Mod-5 synchronous counter circuit by using IC 7476, as shown in Fig. 5. A B C CL input INC, MUTT Fig. 5: Mod-5 synchronous counter 11
2.5. Put each pulse of input signal to the counter circuit and notice the changing of output signal from these 3 flip-flops. 2.6. Record the result in Table 4. Table 4: The result the Mod-5 synchronous counter. Input signal Output signal Clock No. C B A Decade code 1 2 3 4 5 6 7 8 9 10 3. Shift Register 3.1. Make the Shift Register circuit, as shown in Fig. 6. (while connecting logic 1 to all PR and legs). Then, record the result in Table 5. A B C D Input data D D D D CL INC, MUTT Fig. 6: Shift register circuit 12
Table 5: The result the shift register circuit. Input signal Output signal Clock No. Data D C B A 1 0 2 1 3 0 4 1 5 1 6 1 7 0 8 0 9 0 10 1 INC, MUTT 13
uestions 1. Design the Mod-10 synchronous counter and plot its output signals when output signals start at 0000. INC, MUTT 14
2. Design the shift register for transmitting 2 bits data in parallel. INC, MUTT 15