Physics 623Digital CircuitsAug. 4, 20061 Purpose• To introduce the basic principles of digital circuitry.• To understand the small signal response of various gates and circuits typical of currentlyavailable TTL integrated circuitry.2 DiscussionThe circuits are TTL 7400 series of various types from various manufacturers. Use the built-insupply for Vcc= +5 V DC. The logic levels are:• One: 3 to 5.0 volts; nominally 4.75 V.• Zero: 0 to 0.4 volts; nominally ground = 0 V.• Switching Level ∼ 1.4 V.The delay in passing a signal through one NAND gate is typically 13 ns for the SN7400series and is about 7 ns for the 74LS00 series. The fanout capability is 10, (i.e. ten inputs canbe connected to each output). The operating temperature range is from about 0◦C to 70◦C.The general characteristics of TTL logic are described in the attached sheets together with thedetailed specifications of individual chips.Every input of every logical unit you use must be connected to something. Check eachinput pin around the symbol on the data sheet and decide where it should be connected.Some unused inputs may not be shown on the simplified logic diagrams.3 Procedure1. Verify the truth table for a JK flip-flop, using the 74LS112. (The Clock is CP). The datasheet for the out-dated 7473 flip-flop is included for its superior functional block diagram.Study it and see how a JKFF works.Here, J and K refer to the respective input levels w hen the nthclock is high, and Qn+1refers to the output after clock returns from 1 to 0. These flip-flops have a “set” (SD) anda “reset” (CD) feature. Experiment with the SD and CD inputs to determine their effect.See the 74LS112 data sheet.1J K Qn+10 0 Qn0 1 01 0 11 1 Qn2. Connect the 74LS112 JKFF’s to make an 4 bit counter (0 to 15). To display the sequenceof bits use the lights on the board. Don’t forget to hook up all the inputs, even if theyaren’t shown on the functional logic diagram. What do you want the J & K inputs to bein this case? What do you want on the preset and clear lines?L0L1 L2L3.....................= "1"3. Make a ring oscillator.Use an odd number of gates. A signal is propagated around the loop with a speed dependingon the delay of each gate and the number of gates. For 7 gates the period is about 50 -150 nsec., depending on the type of gate. Check the frequency by looking at the outputof any gate with the s cope. Use your four bit counter to count the oscillations. Determinethe gate delay from your measured frequency. Note that a full cycle requires delays goingaround the loop twice. Where must the unused input of each NAND gate be connected?.. .... ..= "1"4. Study the behavior of the monostable multivibrator (oneshot). A dual oneshot has an idnumber 74LS221. Connect the circuit shown. Check the spec sheet for valid resistor andcapacitor values! Arrange the two outputs so that they have the appropriate relative timingwhen triggered by a rising edge. Determine the output pulse width relative to the RC timeconstant of your external circuit. What changes would have to be made to trigger your2circuit on the falling edge? What would the result be if you used the rising-edge triggerinput (B) on the second one-shot? Use the data sheets to determine what to do with theunused inputs. They are not all “true”.Output 1Output 2Triggertime1 ms.3 msR2.5. Investigate the properties of the 8 bit serial-input parallel-output shift register (ID =74HCT164). Connect the chip, then clock various numbers into the register using theswitches. Use the eight LED’s on the breadboard to show the states of the output. Howdoes the “Reset” function work? Keep the circuit set up for the next exercise.6. The 74LS283 is a four bit adder which performs the binary addition of one 4 bit number(A1to A4) to another (B1to B4), including a “carry in ” bit (C0), in order to produce a4-bit sum (S1to S4) plus a “carry out” (C4).Use the shift register to generate both the input binary numbers, so that A1to A4corre-spond to QEthrough QHand B1to B4to QAthrough QD. For convenience it is useful toconnect the input and output 4-bit numbers to a hex display using the TIL311 chip. Verifythe addition.7. Optional – if time permits. Replace the adder with a four bit magnitude comparator(74LS85). Compare the two displayed numbers and verify all the outputs. Now experimentwith the carry inputs to determine what values are required to function