ECET105—Digit al Fundamen talsLab #7 Detailed Directions I. O!ECTI"E1. To test th e operat ion of a 74LS 74 D flip -flo p and compar e the oper ation wi th the predicted behavior2. To test the operation of a 74LS11 2 J-K fli p-flo p and compare the op erati on with the predicted behavior. To meas!r e propa"a tion de la#s o f a 74LS1 12 J- K fli p-flo p 4. To b!ild and t est an en hanced adder- s!btr actorII. $%&T LIT $%!ipment&'() *+ or +ompatible with ,indows 2or i"her/!art!s '' Desi"n Software0e rsion .1 3re%!enc# enerator5scilloscope *arts& 2 6 resistors8 9 , 2 6 :ed L$Ds 1 6 74LS74 d!al D flip-flop 1 6 reen L$D 1 6 74LS112 d!al J-K flip-flop 1 6 S*DT Switch8 D'* confi"!ration 1 6 eS5+ ''' 3*; (oard III. $&OCED'&E %. Te st t(e 7)L 7) D Fli*+Flo* 1. (!ild the D flip -fl op circ!it shown in Figure 7.1. The L$Ds are wired as active-L5, since the flip-flop can s!ppl# more c!rrent in a low state than in a hi"h state. This means that the "reen L$D is on when / is 'and the red L$D indicates / is '. :emember to attach ++ to pin 14 and "ro!nd to pin 7. Course Number: ECET105 Laboratory Number: 7 Page 1 of 14
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1. (!ild the D flip-flop circ!it shown in Figure 7.1. The L$Ds are wired as active-L5,since the flip-flop can s!ppl# more c!rrent in a low state than in a hi"h state. This means
that the "reen L$D is on when / is ' and the red L$D indicates / is '.
:emember to attach ++ to pin 14 and "ro!nd to pin 7.
Course Number: ECET105 Laboratory Number: 7 Page 1 of 14
1. The adder-s!btractor circ!it b!ilt in Lab has a f!ndamental weaBness. ,henever an# of
the inp!ts is chan"ed8 the o!tp!t chan"es. This wo!ld present a si"nificant problem in
b!ildin" a calc!lator since the !ser onl# wants the selected operation to occ!r when the
e%!al b!tton is pressed. ,e can modif# the circ!it from Lab to operate in this wa# b#addin" in flip-flops to store the o!tp!ts onl# on the activation of a clocB si"nal.
2. <sin" /!art!s ''8 modif# the circ!it from Lab as shown in Figure 7. b# addin" three
7474 D-flip-flip chips. Gote that a clear f!nction has been added and that the flip-flop
presets are inactive since the# are tied to M =labeled ++@.
)aBe s!re #o!r circ!it is wired correctl#. 't is eas# to maBe a simple mistaBe and #o! need to
do!ble checB. 5ne wirin" error is "oin" to cost #o! a lot of tro!bleshootin" effort.
Figure 7.—En(anced %dder+ubtractor
. *erform a sim!lation to verif# the correct operation of the circ!it. Gote that in this case
=for the act!al eSoc board@8 the +L5+K si"nal is not a periodic si"nalI the +L5+K si"nalis a discrete si"nal occ!rrin" on a switch clos!re.
Course Number: ECET105 Laboratory Number: 7 Page 10 of 14